/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp

Bug Summary

File:	clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp
Warning:	line 1028, column 43 Called C++ object pointer is null
Annotated Source Code

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clang -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name CStringChecker.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mthread-model posix -mframe-pointer=none -relaxed-aliasing -fmath-errno -fno-rounding-math -masm-verbose -mconstructor-aliases -munwind-tables -target-cpu x86-64 -dwarf-column-info -fno-split-dwarf-inlining -debugger-tuning=gdb -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-10/lib/clang/10.0.0 -D CLANG_VENDOR="Debian " -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/build-llvm/tools/clang/lib/StaticAnalyzer/Checkers -I /build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers -I /build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/include -I /build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/build-llvm/tools/clang/include -I /build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/build-llvm/include -I /build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/llvm/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/backward -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-10/lib/clang/10.0.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/build-llvm/tools/clang/lib/StaticAnalyzer/Checkers -fdebug-prefix-map=/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37=. -ferror-limit 19 -fmessage-length 0 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -fobjc-runtime=gcc -fno-common -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -o /tmp/scan-build-2020-01-12-070717-18343-1 -x c++ /build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp
1//= CStringChecker.cpp - Checks calls to C string functions --------*- C++ -*-//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This defines CStringChecker, which is an assortment of checks on calls
10// to functions in <string.h>.
11//
12//===----------------------------------------------------------------------===//

14#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
15#include "InterCheckerAPI.h"
16#include "clang/Basic/CharInfo.h"
17#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
18#include "clang/StaticAnalyzer/Core/Checker.h"
19#include "clang/StaticAnalyzer/Core/CheckerManager.h"
20#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
21#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
22#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
23#include "llvm/ADT/STLExtras.h"
24#include "llvm/ADT/SmallString.h"
25#include "llvm/Support/raw_ostream.h"

27using namespace clang;
28using namespace ento;

30namespace {
31enum class ConcatFnKind { none = 0, strcat = 1, strlcat = 2 };
32class CStringChecker : public Checker< eval::Call,
                                       check::PreStmt<DeclStmt>,
                                       check::LiveSymbols,
                                       check::DeadSymbols,
                                       check::RegionChanges
                                       > {
mutable std::unique_ptr<BugType> BT_Null, BT_Bounds, BT_Overlap,
    BT_NotCString, BT_AdditionOverflow;

mutable const char *CurrentFunctionDescription;

43public:
/// The filter is used to filter out the diagnostics which are not enabled by
/// the user.
struct CStringChecksFilter {
  DefaultBool CheckCStringNullArg;
  DefaultBool CheckCStringOutOfBounds;
  DefaultBool CheckCStringBufferOverlap;
  DefaultBool CheckCStringNotNullTerm;

  CheckerNameRef CheckNameCStringNullArg;
  CheckerNameRef CheckNameCStringOutOfBounds;
  CheckerNameRef CheckNameCStringBufferOverlap;
  CheckerNameRef CheckNameCStringNotNullTerm;
};

CStringChecksFilter Filter;

static void *getTag() { static int tag; return &tag; }

bool evalCall(const CallEvent &Call, CheckerContext &C) const;
void checkPreStmt(const DeclStmt *DS, CheckerContext &C) const;
void checkLiveSymbols(ProgramStateRef state, SymbolReaper &SR) const;
void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const;

ProgramStateRef
  checkRegionChanges(ProgramStateRef state,
                     const InvalidatedSymbols *,
                     ArrayRef<const MemRegion *> ExplicitRegions,
                     ArrayRef<const MemRegion *> Regions,
                     const LocationContext *LCtx,
                     const CallEvent *Call) const;

typedef void (CStringChecker::*FnCheck)(CheckerContext &,
                                        const CallExpr *) const;
CallDescriptionMap<FnCheck> Callbacks = {
    {{CDF_MaybeBuiltin, "memcpy", 3}, &CStringChecker::evalMemcpy},
    {{CDF_MaybeBuiltin, "mempcpy", 3}, &CStringChecker::evalMempcpy},
    {{CDF_MaybeBuiltin, "memcmp", 3}, &CStringChecker::evalMemcmp},
    {{CDF_MaybeBuiltin, "memmove", 3}, &CStringChecker::evalMemmove},
    {{CDF_MaybeBuiltin, "memset", 3}, &CStringChecker::evalMemset},
    {{CDF_MaybeBuiltin, "explicit_memset", 3}, &CStringChecker::evalMemset},
    {{CDF_MaybeBuiltin, "strcpy", 2}, &CStringChecker::evalStrcpy},
    {{CDF_MaybeBuiltin, "strncpy", 3}, &CStringChecker::evalStrncpy},
    {{CDF_MaybeBuiltin, "stpcpy", 2}, &CStringChecker::evalStpcpy},
    {{CDF_MaybeBuiltin, "strlcpy", 3}, &CStringChecker::evalStrlcpy},
    {{CDF_MaybeBuiltin, "strcat", 2}, &CStringChecker::evalStrcat},
    {{CDF_MaybeBuiltin, "strncat", 3}, &CStringChecker::evalStrncat},
    {{CDF_MaybeBuiltin, "strlcat", 3}, &CStringChecker::evalStrlcat},
    {{CDF_MaybeBuiltin, "strlen", 1}, &CStringChecker::evalstrLength},
    {{CDF_MaybeBuiltin, "strnlen", 2}, &CStringChecker::evalstrnLength},
    {{CDF_MaybeBuiltin, "strcmp", 2}, &CStringChecker::evalStrcmp},
    {{CDF_MaybeBuiltin, "strncmp", 3}, &CStringChecker::evalStrncmp},
    {{CDF_MaybeBuiltin, "strcasecmp", 2}, &CStringChecker::evalStrcasecmp},
    {{CDF_MaybeBuiltin, "strncasecmp", 3}, &CStringChecker::evalStrncasecmp},
    {{CDF_MaybeBuiltin, "strsep", 2}, &CStringChecker::evalStrsep},
    {{CDF_MaybeBuiltin, "bcopy", 3}, &CStringChecker::evalBcopy},
    {{CDF_MaybeBuiltin, "bcmp", 3}, &CStringChecker::evalMemcmp},
    {{CDF_MaybeBuiltin, "bzero", 2}, &CStringChecker::evalBzero},
    {{CDF_MaybeBuiltin, "explicit_bzero", 2}, &CStringChecker::evalBzero},
};

// These require a bit of special handling.
CallDescription StdCopy{{"std", "copy"}, 3},
    StdCopyBackward{{"std", "copy_backward"}, 3};

FnCheck identifyCall(const CallEvent &Call, CheckerContext &C) const;
void evalMemcpy(CheckerContext &C, const CallExpr *CE) const;
void evalMempcpy(CheckerContext &C, const CallExpr *CE) const;
void evalMemmove(CheckerContext &C, const CallExpr *CE) const;
void evalBcopy(CheckerContext &C, const CallExpr *CE) const;
void evalCopyCommon(CheckerContext &C, const CallExpr *CE,
                    ProgramStateRef state,
                    const Expr *Size,
                    const Expr *Source,
                    const Expr *Dest,
                    bool Restricted = false,
                    bool IsMempcpy = false) const;

void evalMemcmp(CheckerContext &C, const CallExpr *CE) const;

void evalstrLength(CheckerContext &C, const CallExpr *CE) const;
void evalstrnLength(CheckerContext &C, const CallExpr *CE) const;
void evalstrLengthCommon(CheckerContext &C,
                         const CallExpr *CE,
                         bool IsStrnlen = false) const;

void evalStrcpy(CheckerContext &C, const CallExpr *CE) const;
void evalStrncpy(CheckerContext &C, const CallExpr *CE) const;
void evalStpcpy(CheckerContext &C, const CallExpr *CE) const;
void evalStrlcpy(CheckerContext &C, const CallExpr *CE) const;
void evalStrcpyCommon(CheckerContext &C, const CallExpr *CE, bool ReturnEnd,
                      bool IsBounded, ConcatFnKind appendK,
                      bool returnPtr = true) const;

void evalStrcat(CheckerContext &C, const CallExpr *CE) const;
void evalStrncat(CheckerContext &C, const CallExpr *CE) const;
void evalStrlcat(CheckerContext &C, const CallExpr *CE) const;

void evalStrcmp(CheckerContext &C, const CallExpr *CE) const;
void evalStrncmp(CheckerContext &C, const CallExpr *CE) const;
void evalStrcasecmp(CheckerContext &C, const CallExpr *CE) const;
void evalStrncasecmp(CheckerContext &C, const CallExpr *CE) const;
void evalStrcmpCommon(CheckerContext &C,
                      const CallExpr *CE,
                      bool IsBounded = false,
                      bool IgnoreCase = false) const;

void evalStrsep(CheckerContext &C, const CallExpr *CE) const;

void evalStdCopy(CheckerContext &C, const CallExpr *CE) const;
void evalStdCopyBackward(CheckerContext &C, const CallExpr *CE) const;
void evalStdCopyCommon(CheckerContext &C, const CallExpr *CE) const;
void evalMemset(CheckerContext &C, const CallExpr *CE) const;
void evalBzero(CheckerContext &C, const CallExpr *CE) const;

// Utility methods
std::pair<ProgramStateRef , ProgramStateRef >
static assumeZero(CheckerContext &C,
                  ProgramStateRef state, SVal V, QualType Ty);

static ProgramStateRef setCStringLength(ProgramStateRef state,
                                            const MemRegion *MR,
                                            SVal strLength);
static SVal getCStringLengthForRegion(CheckerContext &C,
                                      ProgramStateRef &state,
                                      const Expr *Ex,
                                      const MemRegion *MR,
                                      bool hypothetical);
SVal getCStringLength(CheckerContext &C,
                      ProgramStateRef &state,
                      const Expr *Ex,
                      SVal Buf,
                      bool hypothetical = false) const;

const StringLiteral *getCStringLiteral(CheckerContext &C,
                                       ProgramStateRef &state,
                                       const Expr *expr,
                                       SVal val) const;

static ProgramStateRef InvalidateBuffer(CheckerContext &C,
                                        ProgramStateRef state,
                                        const Expr *Ex, SVal V,
                                        bool IsSourceBuffer,
                                        const Expr *Size);

static bool SummarizeRegion(raw_ostream &os, ASTContext &Ctx,
                            const MemRegion *MR);

static bool memsetAux(const Expr *DstBuffer, SVal CharE,
                      const Expr *Size, CheckerContext &C,
                      ProgramStateRef &State);

// Re-usable checks
ProgramStateRef checkNonNull(CheckerContext &C,
                                 ProgramStateRef state,
                                 const Expr *S,
                                 SVal l,
                                 unsigned IdxOfArg) const;
ProgramStateRef CheckLocation(CheckerContext &C,
                                  ProgramStateRef state,
                                  const Expr *S,
                                  SVal l,
                                  const char *message = nullptr) const;
ProgramStateRef CheckBufferAccess(CheckerContext &C,
                                      ProgramStateRef state,
                                      const Expr *Size,
                                      const Expr *FirstBuf,
                                      const Expr *SecondBuf,
                                      const char *firstMessage = nullptr,
                                      const char *secondMessage = nullptr,
                                      bool WarnAboutSize = false) const;

ProgramStateRef CheckBufferAccess(CheckerContext &C,
                                      ProgramStateRef state,
                                      const Expr *Size,
                                      const Expr *Buf,
                                      const char *message = nullptr,
                                      bool WarnAboutSize = false) const {
  // This is a convenience overload.
  return CheckBufferAccess(C, state, Size, Buf, nullptr, message, nullptr,
                           WarnAboutSize);
}
ProgramStateRef CheckOverlap(CheckerContext &C,
                                 ProgramStateRef state,
                                 const Expr *Size,
                                 const Expr *First,
                                 const Expr *Second) const;
void emitOverlapBug(CheckerContext &C,
                    ProgramStateRef state,
                    const Stmt *First,
                    const Stmt *Second) const;

void emitNullArgBug(CheckerContext &C, ProgramStateRef State, const Stmt *S,
                    StringRef WarningMsg) const;
void emitOutOfBoundsBug(CheckerContext &C, ProgramStateRef State,
                        const Stmt *S, StringRef WarningMsg) const;
void emitNotCStringBug(CheckerContext &C, ProgramStateRef State,
                       const Stmt *S, StringRef WarningMsg) const;
void emitAdditionOverflowBug(CheckerContext &C, ProgramStateRef State) const;

ProgramStateRef checkAdditionOverflow(CheckerContext &C,
                                          ProgramStateRef state,
                                          NonLoc left,
                                          NonLoc right) const;

// Return true if the destination buffer of the copy function may be in bound.
// Expects SVal of Size to be positive and unsigned.
// Expects SVal of FirstBuf to be a FieldRegion.
static bool IsFirstBufInBound(CheckerContext &C,
                              ProgramStateRef state,
                              const Expr *FirstBuf,
                              const Expr *Size);
255};

257} //end anonymous namespace

259REGISTER_MAP_WITH_PROGRAMSTATE(CStringLength, const MemRegion *, SVal)namespace { class CStringLength {}; using CStringLengthTy = llvm
::ImmutableMap<const MemRegion *, SVal>; } namespace clang
 { namespace ento { template <> struct ProgramStateTrait
<CStringLength> : public ProgramStatePartialTrait<CStringLengthTy
> { static void *GDMIndex() { static int Index; return &
Index; } }; } }

261//===----------------------------------------------------------------------===//
262// Individual checks and utility methods.
263//===----------------------------------------------------------------------===//

265std::pair<ProgramStateRef , ProgramStateRef >
266CStringChecker::assumeZero(CheckerContext &C, ProgramStateRef state, SVal V,
                         QualType Ty) {
Optional<DefinedSVal> val = V.getAs<DefinedSVal>();
if (!val)
  return std::pair<ProgramStateRef , ProgramStateRef >(state, state);

SValBuilder &svalBuilder = C.getSValBuilder();
DefinedOrUnknownSVal zero = svalBuilder.makeZeroVal(Ty);
return state->assume(svalBuilder.evalEQ(state, *val, zero));
275}

277ProgramStateRef CStringChecker::checkNonNull(CheckerContext &C,
                                          ProgramStateRef state,
                                          const Expr *S, SVal l,
                                          unsigned IdxOfArg) const {
// If a previous check has failed, propagate the failure.
if (!state)
  return nullptr;

ProgramStateRef stateNull, stateNonNull;
std::tie(stateNull, stateNonNull) = assumeZero(C, state, l, S->getType());

if (stateNull && !stateNonNull) {
  if (Filter.CheckCStringNullArg) {
    SmallString<80> buf;
    llvm::raw_svector_ostream OS(buf);
    assert(CurrentFunctionDescription)((CurrentFunctionDescription) ? static_cast<void> (0) :
 __assert_fail ("CurrentFunctionDescription", "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 292, __PRETTY_FUNCTION__));
    OS << "Null pointer passed as " << IdxOfArg
       << llvm::getOrdinalSuffix(IdxOfArg) << " argument to "
       << CurrentFunctionDescription;

    emitNullArgBug(C, stateNull, S, OS.str());
  }
  return nullptr;
}

// From here on, assume that the value is non-null.
assert(stateNonNull)((stateNonNull) ? static_cast<void> (0) : __assert_fail
 ("stateNonNull", "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 303, __PRETTY_FUNCTION__));
return stateNonNull;
305}

307// FIXME: This was originally copied from ArrayBoundChecker.cpp. Refactor?
308ProgramStateRef CStringChecker::CheckLocation(CheckerContext &C,
                                           ProgramStateRef state,
                                           const Expr *S, SVal l,
                                           const char *warningMsg) const {
// If a previous check has failed, propagate the failure.
if (!state)
  return nullptr;

// Check for out of bound array element access.
const MemRegion *R = l.getAsRegion();
if (!R)
  return state;

const ElementRegion *ER = dyn_cast<ElementRegion>(R);
if (!ER)
  return state;

if (ER->getValueType() != C.getASTContext().CharTy)
  return state;

// Get the size of the array.
const SubRegion *superReg = cast<SubRegion>(ER->getSuperRegion());
SValBuilder &svalBuilder = C.getSValBuilder();
SVal Extent =
  svalBuilder.convertToArrayIndex(superReg->getExtent(svalBuilder));
DefinedOrUnknownSVal Size = Extent.castAs<DefinedOrUnknownSVal>();

// Get the index of the accessed element.
DefinedOrUnknownSVal Idx = ER->getIndex().castAs<DefinedOrUnknownSVal>();

ProgramStateRef StInBound = state->assumeInBound(Idx, Size, true);
ProgramStateRef StOutBound = state->assumeInBound(Idx, Size, false);
if (StOutBound && !StInBound) {
  // These checks are either enabled by the CString out-of-bounds checker
  // explicitly or implicitly by the Malloc checker.
  // In the latter case we only do modeling but do not emit warning.
  if (!Filter.CheckCStringOutOfBounds)
    return nullptr;
  // Emit a bug report.
  if (warningMsg) {
    emitOutOfBoundsBug(C, StOutBound, S, warningMsg);
  } else {
    assert(CurrentFunctionDescription)((CurrentFunctionDescription) ? static_cast<void> (0) :
 __assert_fail ("CurrentFunctionDescription", "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 350, __PRETTY_FUNCTION__));
    assert(CurrentFunctionDescription[0] != '\0')((CurrentFunctionDescription[0] != '\0') ? static_cast<void
> (0) : __assert_fail ("CurrentFunctionDescription[0] != '\\0'"
, "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 351, __PRETTY_FUNCTION__));

    SmallString<80> buf;
    llvm::raw_svector_ostream os(buf);
    os << toUppercase(CurrentFunctionDescription[0])
       << &CurrentFunctionDescription[1]
       << " accesses out-of-bound array element";
    emitOutOfBoundsBug(C, StOutBound, S, os.str());
  }
  return nullptr;
}

// Array bound check succeeded.  From this point forward the array bound
// should always succeed.
return StInBound;
366}

368ProgramStateRef CStringChecker::CheckBufferAccess(CheckerContext &C,
                                               ProgramStateRef state,
                                               const Expr *Size,
                                               const Expr *FirstBuf,
                                               const Expr *SecondBuf,
                                               const char *firstMessage,
                                               const char *secondMessage,
                                               bool WarnAboutSize) const {
// If a previous check has failed, propagate the failure.
if (!state)
  return nullptr;

SValBuilder &svalBuilder = C.getSValBuilder();
ASTContext &Ctx = svalBuilder.getContext();
const LocationContext *LCtx = C.getLocationContext();

QualType sizeTy = Size->getType();
QualType PtrTy = Ctx.getPointerType(Ctx.CharTy);

// Check that the first buffer is non-null.
SVal BufVal = C.getSVal(FirstBuf);
state = checkNonNull(C, state, FirstBuf, BufVal, 1);
if (!state)
  return nullptr;

// If out-of-bounds checking is turned off, skip the rest.
if (!Filter.CheckCStringOutOfBounds)
  return state;

// Get the access length and make sure it is known.
// FIXME: This assumes the caller has already checked that the access length
// is positive. And that it's unsigned.
SVal LengthVal = C.getSVal(Size);
Optional<NonLoc> Length = LengthVal.getAs<NonLoc>();
if (!Length)
  return state;

// Compute the offset of the last element to be accessed: size-1.
NonLoc One = svalBuilder.makeIntVal(1, sizeTy).castAs<NonLoc>();
SVal Offset = svalBuilder.evalBinOpNN(state, BO_Sub, *Length, One, sizeTy);
if (Offset.isUnknown())
  return nullptr;
NonLoc LastOffset = Offset.castAs<NonLoc>();

// Check that the first buffer is sufficiently long.
SVal BufStart = svalBuilder.evalCast(BufVal, PtrTy, FirstBuf->getType());
if (Optional<Loc> BufLoc = BufStart.getAs<Loc>()) {
  const Expr *warningExpr = (WarnAboutSize ? Size : FirstBuf);

  SVal BufEnd = svalBuilder.evalBinOpLN(state, BO_Add, *BufLoc,
                                        LastOffset, PtrTy);
  state = CheckLocation(C, state, warningExpr, BufEnd, firstMessage);

  // If the buffer isn't large enough, abort.
  if (!state)
    return nullptr;
}

// If there's a second buffer, check it as well.
if (SecondBuf) {
  BufVal = state->getSVal(SecondBuf, LCtx);
  state = checkNonNull(C, state, SecondBuf, BufVal, 2);
  if (!state)
    return nullptr;

  BufStart = svalBuilder.evalCast(BufVal, PtrTy, SecondBuf->getType());
  if (Optional<Loc> BufLoc = BufStart.getAs<Loc>()) {
    const Expr *warningExpr = (WarnAboutSize ? Size : SecondBuf);

    SVal BufEnd = svalBuilder.evalBinOpLN(state, BO_Add, *BufLoc,
                                          LastOffset, PtrTy);
    state = CheckLocation(C, state, warningExpr, BufEnd, secondMessage);
  }
}

// Large enough or not, return this state!
return state;
445}

447ProgramStateRef CStringChecker::CheckOverlap(CheckerContext &C,
                                          ProgramStateRef state,
                                          const Expr *Size,
                                          const Expr *First,
                                          const Expr *Second) const {
if (!Filter.CheckCStringBufferOverlap)
  return state;

// Do a simple check for overlap: if the two arguments are from the same
// buffer, see if the end of the first is greater than the start of the second
// or vice versa.

// If a previous check has failed, propagate the failure.
if (!state)
  return nullptr;

ProgramStateRef stateTrue, stateFalse;

// Get the buffer values and make sure they're known locations.
const LocationContext *LCtx = C.getLocationContext();
SVal firstVal = state->getSVal(First, LCtx);
SVal secondVal = state->getSVal(Second, LCtx);

Optional<Loc> firstLoc = firstVal.getAs<Loc>();
if (!firstLoc)
  return state;

Optional<Loc> secondLoc = secondVal.getAs<Loc>();
if (!secondLoc)
  return state;

// Are the two values the same?
SValBuilder &svalBuilder = C.getSValBuilder();
std::tie(stateTrue, stateFalse) =
  state->assume(svalBuilder.evalEQ(state, *firstLoc, *secondLoc));

if (stateTrue && !stateFalse) {
  // If the values are known to be equal, that's automatically an overlap.
  emitOverlapBug(C, stateTrue, First, Second);
  return nullptr;
}

// assume the two expressions are not equal.
assert(stateFalse)((stateFalse) ? static_cast<void> (0) : __assert_fail (
"stateFalse", "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 490, __PRETTY_FUNCTION__));
state = stateFalse;

// Which value comes first?
QualType cmpTy = svalBuilder.getConditionType();
SVal reverse = svalBuilder.evalBinOpLL(state, BO_GT,
                                       *firstLoc, *secondLoc, cmpTy);
Optional<DefinedOrUnknownSVal> reverseTest =
    reverse.getAs<DefinedOrUnknownSVal>();
if (!reverseTest)
  return state;

std::tie(stateTrue, stateFalse) = state->assume(*reverseTest);
if (stateTrue) {
  if (stateFalse) {
    // If we don't know which one comes first, we can't perform this test.
    return state;
  } else {
    // Switch the values so that firstVal is before secondVal.
    std::swap(firstLoc, secondLoc);

    // Switch the Exprs as well, so that they still correspond.
    std::swap(First, Second);
  }
}

// Get the length, and make sure it too is known.
SVal LengthVal = state->getSVal(Size, LCtx);
Optional<NonLoc> Length = LengthVal.getAs<NonLoc>();
if (!Length)
  return state;

// Convert the first buffer's start address to char*.
// Bail out if the cast fails.
ASTContext &Ctx = svalBuilder.getContext();
QualType CharPtrTy = Ctx.getPointerType(Ctx.CharTy);
SVal FirstStart = svalBuilder.evalCast(*firstLoc, CharPtrTy,
                                       First->getType());
Optional<Loc> FirstStartLoc = FirstStart.getAs<Loc>();
if (!FirstStartLoc)
  return state;

// Compute the end of the first buffer. Bail out if THAT fails.
SVal FirstEnd = svalBuilder.evalBinOpLN(state, BO_Add,
                               *FirstStartLoc, *Length, CharPtrTy);
Optional<Loc> FirstEndLoc = FirstEnd.getAs<Loc>();
if (!FirstEndLoc)
  return state;

// Is the end of the first buffer past the start of the second buffer?
SVal Overlap = svalBuilder.evalBinOpLL(state, BO_GT,
                              *FirstEndLoc, *secondLoc, cmpTy);
Optional<DefinedOrUnknownSVal> OverlapTest =
    Overlap.getAs<DefinedOrUnknownSVal>();
if (!OverlapTest)
  return state;

std::tie(stateTrue, stateFalse) = state->assume(*OverlapTest);

if (stateTrue && !stateFalse) {
  // Overlap!
  emitOverlapBug(C, stateTrue, First, Second);
  return nullptr;
}

// assume the two expressions don't overlap.
assert(stateFalse)((stateFalse) ? static_cast<void> (0) : __assert_fail (
"stateFalse", "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 556, __PRETTY_FUNCTION__));
return stateFalse;
558}

560void CStringChecker::emitOverlapBug(CheckerContext &C, ProgramStateRef state,
                                const Stmt *First, const Stmt *Second) const {
ExplodedNode *N = C.generateErrorNode(state);
if (!N)
  return;

if (!BT_Overlap)
  BT_Overlap.reset(new BugType(Filter.CheckNameCStringBufferOverlap,
                               categories::UnixAPI, "Improper arguments"));

// Generate a report for this bug.
auto report = std::make_unique<PathSensitiveBugReport>(
    *BT_Overlap, "Arguments must not be overlapping buffers", N);
report->addRange(First->getSourceRange());
report->addRange(Second->getSourceRange());

C.emitReport(std::move(report));
577}

579void CStringChecker::emitNullArgBug(CheckerContext &C, ProgramStateRef State,
                                  const Stmt *S, StringRef WarningMsg) const {
if (ExplodedNode *N = C.generateErrorNode(State)) {
  if (!BT_Null)
    BT_Null.reset(new BuiltinBug(
        Filter.CheckNameCStringNullArg, categories::UnixAPI,
        "Null pointer argument in call to byte string function"));

  BuiltinBug *BT = static_cast<BuiltinBug *>(BT_Null.get());
  auto Report = std::make_unique<PathSensitiveBugReport>(*BT, WarningMsg, N);
  Report->addRange(S->getSourceRange());
  if (const auto *Ex = dyn_cast<Expr>(S))
    bugreporter::trackExpressionValue(N, Ex, *Report);
  C.emitReport(std::move(Report));
}
594}

596void CStringChecker::emitOutOfBoundsBug(CheckerContext &C,
                                      ProgramStateRef State, const Stmt *S,
                                      StringRef WarningMsg) const {
if (ExplodedNode *N = C.generateErrorNode(State)) {
  if (!BT_Bounds)
    BT_Bounds.reset(new BuiltinBug(
        Filter.CheckCStringOutOfBounds ? Filter.CheckNameCStringOutOfBounds
                                       : Filter.CheckNameCStringNullArg,
        "Out-of-bound array access",
        "Byte string function accesses out-of-bound array element"));

  BuiltinBug *BT = static_cast<BuiltinBug *>(BT_Bounds.get());

  // FIXME: It would be nice to eventually make this diagnostic more clear,
  // e.g., by referencing the original declaration or by saying *why* this
  // reference is outside the range.
  auto Report = std::make_unique<PathSensitiveBugReport>(*BT, WarningMsg, N);
  Report->addRange(S->getSourceRange());
  C.emitReport(std::move(Report));
}
616}

618void CStringChecker::emitNotCStringBug(CheckerContext &C, ProgramStateRef State,
                                     const Stmt *S,
                                     StringRef WarningMsg) const {
if (ExplodedNode *N = C.generateNonFatalErrorNode(State)) {
  if (!BT_NotCString)
    BT_NotCString.reset(new BuiltinBug(
        Filter.CheckNameCStringNotNullTerm, categories::UnixAPI,
        "Argument is not a null-terminated string."));

  auto Report =
      std::make_unique<PathSensitiveBugReport>(*BT_NotCString, WarningMsg, N);

  Report->addRange(S->getSourceRange());
  C.emitReport(std::move(Report));
}
633}

635void CStringChecker::emitAdditionOverflowBug(CheckerContext &C,
                                           ProgramStateRef State) const {
if (ExplodedNode *N = C.generateErrorNode(State)) {
  if (!BT_NotCString)
    BT_NotCString.reset(
        new BuiltinBug(Filter.CheckNameCStringOutOfBounds, "API",
                       "Sum of expressions causes overflow."));

  // This isn't a great error message, but this should never occur in real
  // code anyway -- you'd have to create a buffer longer than a size_t can
  // represent, which is sort of a contradiction.
  const char *WarningMsg =
      "This expression will create a string whose length is too big to "
      "be represented as a size_t";

  auto Report =
      std::make_unique<PathSensitiveBugReport>(*BT_NotCString, WarningMsg, N);
  C.emitReport(std::move(Report));
}
654}

656ProgramStateRef CStringChecker::checkAdditionOverflow(CheckerContext &C,
                                                   ProgramStateRef state,
                                                   NonLoc left,
                                                   NonLoc right) const {
// If out-of-bounds checking is turned off, skip the rest.
if (!Filter.CheckCStringOutOfBounds)
  return state;

// If a previous check has failed, propagate the failure.
if (!state)
  return nullptr;

SValBuilder &svalBuilder = C.getSValBuilder();
BasicValueFactory &BVF = svalBuilder.getBasicValueFactory();

QualType sizeTy = svalBuilder.getContext().getSizeType();
const llvm::APSInt &maxValInt = BVF.getMaxValue(sizeTy);
NonLoc maxVal = svalBuilder.makeIntVal(maxValInt);

SVal maxMinusRight;
if (right.getAs<nonloc::ConcreteInt>()) {
  maxMinusRight = svalBuilder.evalBinOpNN(state, BO_Sub, maxVal, right,
                                               sizeTy);
} else {
  // Try switching the operands. (The order of these two assignments is
  // important!)
  maxMinusRight = svalBuilder.evalBinOpNN(state, BO_Sub, maxVal, left,
                                          sizeTy);
  left = right;
}

if (Optional<NonLoc> maxMinusRightNL = maxMinusRight.getAs<NonLoc>()) {
  QualType cmpTy = svalBuilder.getConditionType();
  // If left > max - right, we have an overflow.
  SVal willOverflow = svalBuilder.evalBinOpNN(state, BO_GT, left,
                                              *maxMinusRightNL, cmpTy);

  ProgramStateRef stateOverflow, stateOkay;
  std::tie(stateOverflow, stateOkay) =
    state->assume(willOverflow.castAs<DefinedOrUnknownSVal>());

  if (stateOverflow && !stateOkay) {
    // We have an overflow. Emit a bug report.
    emitAdditionOverflowBug(C, stateOverflow);
    return nullptr;
  }

  // From now on, assume an overflow didn't occur.
  assert(stateOkay)((stateOkay) ? static_cast<void> (0) : __assert_fail ("stateOkay"
, "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 704, __PRETTY_FUNCTION__));
  state = stateOkay;
}

return state;
709}

711ProgramStateRef CStringChecker::setCStringLength(ProgramStateRef state,
                                              const MemRegion *MR,
                                              SVal strLength) {
assert(!strLength.isUndef() && "Attempt to set an undefined string length")((!strLength.isUndef() && "Attempt to set an undefined string length"
) ? static_cast<void> (0) : __assert_fail ("!strLength.isUndef() && \"Attempt to set an undefined string length\""
, "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 714, __PRETTY_FUNCTION__));

MR = MR->StripCasts();

switch (MR->getKind()) {
case MemRegion::StringRegionKind:
  // FIXME: This can happen if we strcpy() into a string region. This is
  // undefined [C99 6.4.5p6], but we should still warn about it.
  return state;

case MemRegion::SymbolicRegionKind:
case MemRegion::AllocaRegionKind:
case MemRegion::VarRegionKind:
case MemRegion::FieldRegionKind:
case MemRegion::ObjCIvarRegionKind:
  // These are the types we can currently track string lengths for.
  break;

case MemRegion::ElementRegionKind:
  // FIXME: Handle element regions by upper-bounding the parent region's
  // string length.
  return state;

default:
  // Other regions (mostly non-data) can't have a reliable C string length.
  // For now, just ignore the change.
  // FIXME: These are rare but not impossible. We should output some kind of
  // warning for things like strcpy((char[]){'a', 0}, "b");
  return state;
}

if (strLength.isUnknown())
  return state->remove<CStringLength>(MR);

return state->set<CStringLength>(MR, strLength);
749}

751SVal CStringChecker::getCStringLengthForRegion(CheckerContext &C,
                                             ProgramStateRef &state,
                                             const Expr *Ex,
                                             const MemRegion *MR,
                                             bool hypothetical) {
if (!hypothetical) {
  // If there's a recorded length, go ahead and return it.
  const SVal *Recorded = state->get<CStringLength>(MR);
  if (Recorded)
    return *Recorded;
}

// Otherwise, get a new symbol and update the state.
SValBuilder &svalBuilder = C.getSValBuilder();
QualType sizeTy = svalBuilder.getContext().getSizeType();
SVal strLength = svalBuilder.getMetadataSymbolVal(CStringChecker::getTag(),
                                                  MR, Ex, sizeTy,
                                                  C.getLocationContext(),
                                                  C.blockCount());

if (!hypothetical) {
  if (Optional<NonLoc> strLn = strLength.getAs<NonLoc>()) {
    // In case of unbounded calls strlen etc bound the range to SIZE_MAX/4
    BasicValueFactory &BVF = svalBuilder.getBasicValueFactory();
    const llvm::APSInt &maxValInt = BVF.getMaxValue(sizeTy);
    llvm::APSInt fourInt = APSIntType(maxValInt).getValue(4);
    const llvm::APSInt *maxLengthInt = BVF.evalAPSInt(BO_Div, maxValInt,
                                                      fourInt);
    NonLoc maxLength = svalBuilder.makeIntVal(*maxLengthInt);
    SVal evalLength = svalBuilder.evalBinOpNN(state, BO_LE, *strLn,
                                              maxLength, sizeTy);
    state = state->assume(evalLength.castAs<DefinedOrUnknownSVal>(), true);
  }
  state = state->set<CStringLength>(MR, strLength);
}

return strLength;
788}

790SVal CStringChecker::getCStringLength(CheckerContext &C, ProgramStateRef &state,
                                    const Expr *Ex, SVal Buf,
                                    bool hypothetical) const {
const MemRegion *MR = Buf.getAsRegion();
if (!MR) {
5
←
Assuming 'MR' is non-null→
6
←
Taking false branch→
  // If we can't get a region, see if it's something we /know/ isn't a
  // C string. In the context of locations, the only time we can issue such
  // a warning is for labels.
  if (Optional<loc::GotoLabel> Label = Buf.getAs<loc::GotoLabel>()) {
    if (Filter.CheckCStringNotNullTerm) {
      SmallString<120> buf;
      llvm::raw_svector_ostream os(buf);
      assert(CurrentFunctionDescription)((CurrentFunctionDescription) ? static_cast<void> (0) :
 __assert_fail ("CurrentFunctionDescription", "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 802, __PRETTY_FUNCTION__));
      os << "Argument to " << CurrentFunctionDescription
         << " is the address of the label '" << Label->getLabel()->getName()
         << "', which is not a null-terminated string";

      emitNotCStringBug(C, state, Ex, os.str());
    }
    return UndefinedVal();
  }

  // If it's not a region and not a label, give up.
  return UnknownVal();
}

// If we have a region, strip casts from it and see if we can figure out
// its length. For anything we can't figure out, just return UnknownVal.
MR = MR->StripCasts();

switch (MR->getKind()) {
7
←
Control jumps to the 'default' case at line 842→
case MemRegion::StringRegionKind: {
  // Modifying the contents of string regions is undefined [C99 6.4.5p6],
  // so we can assume that the byte length is the correct C string length.
  SValBuilder &svalBuilder = C.getSValBuilder();
  QualType sizeTy = svalBuilder.getContext().getSizeType();
  const StringLiteral *strLit = cast<StringRegion>(MR)->getStringLiteral();
  return svalBuilder.makeIntVal(strLit->getByteLength(), sizeTy);
}
case MemRegion::SymbolicRegionKind:
case MemRegion::AllocaRegionKind:
case MemRegion::VarRegionKind:
case MemRegion::FieldRegionKind:
case MemRegion::ObjCIvarRegionKind:
  return getCStringLengthForRegion(C, state, Ex, MR, hypothetical);
case MemRegion::CompoundLiteralRegionKind:
  // FIXME: Can we track this? Is it necessary?
  return UnknownVal();
case MemRegion::ElementRegionKind:
  // FIXME: How can we handle this? It's not good enough to subtract the
  // offset from the base string length; consider "123\x00567" and &a[5].
  return UnknownVal();
default:
  // Other regions (mostly non-data) can't have a reliable C string length.
  // In this case, an error is emitted and UndefinedVal is returned.
  // The caller should always be prepared to handle this case.
  if (Filter.CheckCStringNotNullTerm) {
8
←
Assuming the condition is true→
9
←
Taking true branch→
    SmallString<120> buf;
    llvm::raw_svector_ostream os(buf);

    assert9.1
Field 'CurrentFunctionDescription' is non-null
(CurrentFunctionDescription)((CurrentFunctionDescription) ? static_cast<void> (0) :
 __assert_fail ("CurrentFunctionDescription", "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 850, __PRETTY_FUNCTION__));
10
←
'?' condition is true→
    os << "Argument to " << CurrentFunctionDescription << " is ";

    if (SummarizeRegion(os, C.getASTContext(), MR))
11
←
Calling 'CStringChecker::SummarizeRegion'→
      os << ", which is not a null-terminated string";
    else
      os << "not a null-terminated string";

    emitNotCStringBug(C, state, Ex, os.str());
  }
  return UndefinedVal();
}
862}

864const StringLiteral *CStringChecker::getCStringLiteral(CheckerContext &C,
ProgramStateRef &state, const Expr *expr, SVal val) const {

// Get the memory region pointed to by the val.
const MemRegion *bufRegion = val.getAsRegion();
if (!bufRegion)
  return nullptr;

// Strip casts off the memory region.
bufRegion = bufRegion->StripCasts();

// Cast the memory region to a string region.
const StringRegion *strRegion= dyn_cast<StringRegion>(bufRegion);
if (!strRegion)
  return nullptr;

// Return the actual string in the string region.
return strRegion->getStringLiteral();
882}

884bool CStringChecker::IsFirstBufInBound(CheckerContext &C,
                                     ProgramStateRef state,
                                     const Expr *FirstBuf,
                                     const Expr *Size) {
// If we do not know that the buffer is long enough we return 'true'.
// Otherwise the parent region of this field region would also get
// invalidated, which would lead to warnings based on an unknown state.

// Originally copied from CheckBufferAccess and CheckLocation.
SValBuilder &svalBuilder = C.getSValBuilder();
ASTContext &Ctx = svalBuilder.getContext();
const LocationContext *LCtx = C.getLocationContext();

QualType sizeTy = Size->getType();
QualType PtrTy = Ctx.getPointerType(Ctx.CharTy);
SVal BufVal = state->getSVal(FirstBuf, LCtx);

SVal LengthVal = state->getSVal(Size, LCtx);
Optional<NonLoc> Length = LengthVal.getAs<NonLoc>();
if (!Length)
  return true; // cf top comment.

// Compute the offset of the last element to be accessed: size-1.
NonLoc One = svalBuilder.makeIntVal(1, sizeTy).castAs<NonLoc>();
SVal Offset = svalBuilder.evalBinOpNN(state, BO_Sub, *Length, One, sizeTy);
if (Offset.isUnknown())
  return true; // cf top comment
NonLoc LastOffset = Offset.castAs<NonLoc>();

// Check that the first buffer is sufficiently long.
SVal BufStart = svalBuilder.evalCast(BufVal, PtrTy, FirstBuf->getType());
Optional<Loc> BufLoc = BufStart.getAs<Loc>();
if (!BufLoc)
  return true; // cf top comment.

SVal BufEnd =
    svalBuilder.evalBinOpLN(state, BO_Add, *BufLoc, LastOffset, PtrTy);

// Check for out of bound array element access.
const MemRegion *R = BufEnd.getAsRegion();
if (!R)
  return true; // cf top comment.

const ElementRegion *ER = dyn_cast<ElementRegion>(R);
if (!ER)
  return true; // cf top comment.

// FIXME: Does this crash when a non-standard definition
// of a library function is encountered?
assert(ER->getValueType() == C.getASTContext().CharTy &&((ER->getValueType() == C.getASTContext().CharTy &&
 "IsFirstBufInBound should only be called with char* ElementRegions"
) ? static_cast<void> (0) : __assert_fail ("ER->getValueType() == C.getASTContext().CharTy && \"IsFirstBufInBound should only be called with char* ElementRegions\""
, "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 934, __PRETTY_FUNCTION__))
       "IsFirstBufInBound should only be called with char* ElementRegions")((ER->getValueType() == C.getASTContext().CharTy &&
 "IsFirstBufInBound should only be called with char* ElementRegions"
) ? static_cast<void> (0) : __assert_fail ("ER->getValueType() == C.getASTContext().CharTy && \"IsFirstBufInBound should only be called with char* ElementRegions\""
, "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 934, __PRETTY_FUNCTION__));

// Get the size of the array.
const SubRegion *superReg = cast<SubRegion>(ER->getSuperRegion());
SVal Extent =
    svalBuilder.convertToArrayIndex(superReg->getExtent(svalBuilder));
DefinedOrUnknownSVal ExtentSize = Extent.castAs<DefinedOrUnknownSVal>();

// Get the index of the accessed element.
DefinedOrUnknownSVal Idx = ER->getIndex().castAs<DefinedOrUnknownSVal>();

ProgramStateRef StInBound = state->assumeInBound(Idx, ExtentSize, true);

return static_cast<bool>(StInBound);
948}

950ProgramStateRef CStringChecker::InvalidateBuffer(CheckerContext &C,
                                               ProgramStateRef state,
                                               const Expr *E, SVal V,
                                               bool IsSourceBuffer,
                                               const Expr *Size) {
Optional<Loc> L = V.getAs<Loc>();
if (!L)
  return state;

// FIXME: This is a simplified version of what's in CFRefCount.cpp -- it makes
// some assumptions about the value that CFRefCount can't. Even so, it should
// probably be refactored.
if (Optional<loc::MemRegionVal> MR = L->getAs<loc::MemRegionVal>()) {
  const MemRegion *R = MR->getRegion()->StripCasts();

  // Are we dealing with an ElementRegion?  If so, we should be invalidating
  // the super-region.
  if (const ElementRegion *ER = dyn_cast<ElementRegion>(R)) {
    R = ER->getSuperRegion();
    // FIXME: What about layers of ElementRegions?
  }

  // Invalidate this region.
  const LocationContext *LCtx = C.getPredecessor()->getLocationContext();

  bool CausesPointerEscape = false;
  RegionAndSymbolInvalidationTraits ITraits;
  // Invalidate and escape only indirect regions accessible through the source
  // buffer.
  if (IsSourceBuffer) {
    ITraits.setTrait(R->getBaseRegion(),
                     RegionAndSymbolInvalidationTraits::TK_PreserveContents);
    ITraits.setTrait(R, RegionAndSymbolInvalidationTraits::TK_SuppressEscape);
    CausesPointerEscape = true;
  } else {
    const MemRegion::Kind& K = R->getKind();
    if (K == MemRegion::FieldRegionKind)
      if (Size && IsFirstBufInBound(C, state, E, Size)) {
        // If destination buffer is a field region and access is in bound,
        // do not invalidate its super region.
        ITraits.setTrait(
            R,
            RegionAndSymbolInvalidationTraits::TK_DoNotInvalidateSuperRegion);
      }
  }

  return state->invalidateRegions(R, E, C.blockCount(), LCtx,
                                  CausesPointerEscape, nullptr, nullptr,
                                  &ITraits);
}

// If we have a non-region value by chance, just remove the binding.
// FIXME: is this necessary or correct? This handles the non-Region
//  cases.  Is it ever valid to store to these?
return state->killBinding(*L);
1005}

1007bool CStringChecker::SummarizeRegion(raw_ostream &os, ASTContext &Ctx,
                                   const MemRegion *MR) {
const TypedValueRegion *TVR = dyn_cast<TypedValueRegion>(MR);
12
←
Assuming 'MR' is not a 'TypedValueRegion'→
13
←
'TVR' initialized to a null pointer value→

switch (MR->getKind()) {
14
←
Control jumps to 'case CXXTempObjectRegionKind:'  at line 1027→
case MemRegion::FunctionCodeRegionKind: {
  const NamedDecl *FD = cast<FunctionCodeRegion>(MR)->getDecl();
  if (FD)
    os << "the address of the function '" << *FD << '\'';
  else
    os << "the address of a function";
  return true;
}
case MemRegion::BlockCodeRegionKind:
  os << "block text";
  return true;
case MemRegion::BlockDataRegionKind:
  os << "a block";
  return true;
case MemRegion::CXXThisRegionKind:
case MemRegion::CXXTempObjectRegionKind:
  os << "a C++ temp object of type " << TVR->getValueType().getAsString();
15
←
Called C++ object pointer is null
  return true;
case MemRegion::VarRegionKind:
  os << "a variable of type" << TVR->getValueType().getAsString();
  return true;
case MemRegion::FieldRegionKind:
  os << "a field of type " << TVR->getValueType().getAsString();
  return true;
case MemRegion::ObjCIvarRegionKind:
  os << "an instance variable of type " << TVR->getValueType().getAsString();
  return true;
default:
  return false;
}
1042}

1044bool CStringChecker::memsetAux(const Expr *DstBuffer, SVal CharVal,
                             const Expr *Size, CheckerContext &C,
                             ProgramStateRef &State) {
SVal MemVal = C.getSVal(DstBuffer);
SVal SizeVal = C.getSVal(Size);
const MemRegion *MR = MemVal.getAsRegion();
if (!MR)
  return false;

// We're about to model memset by producing a "default binding" in the Store.
// Our current implementation - RegionStore - doesn't support default bindings
// that don't cover the whole base region. So we should first get the offset
// and the base region to figure out whether the offset of buffer is 0.
RegionOffset Offset = MR->getAsOffset();
const MemRegion *BR = Offset.getRegion();

Optional<NonLoc> SizeNL = SizeVal.getAs<NonLoc>();
if (!SizeNL)
  return false;

SValBuilder &svalBuilder = C.getSValBuilder();
ASTContext &Ctx = C.getASTContext();

// void *memset(void *dest, int ch, size_t count);
// For now we can only handle the case of offset is 0 and concrete char value.
if (Offset.isValid() && !Offset.hasSymbolicOffset() &&
    Offset.getOffset() == 0) {
  // Get the base region's extent.
  auto *SubReg = cast<SubRegion>(BR);
  DefinedOrUnknownSVal Extent = SubReg->getExtent(svalBuilder);

  ProgramStateRef StateWholeReg, StateNotWholeReg;
  std::tie(StateWholeReg, StateNotWholeReg) =
      State->assume(svalBuilder.evalEQ(State, Extent, *SizeNL));

  // With the semantic of 'memset()', we should convert the CharVal to
  // unsigned char.
  CharVal = svalBuilder.evalCast(CharVal, Ctx.UnsignedCharTy, Ctx.IntTy);

  ProgramStateRef StateNullChar, StateNonNullChar;
  std::tie(StateNullChar, StateNonNullChar) =
      assumeZero(C, State, CharVal, Ctx.UnsignedCharTy);

  if (StateWholeReg && !StateNotWholeReg && StateNullChar &&
      !StateNonNullChar) {
    // If the 'memset()' acts on the whole region of destination buffer and
    // the value of the second argument of 'memset()' is zero, bind the second
    // argument's value to the destination buffer with 'default binding'.
    // FIXME: Since there is no perfect way to bind the non-zero character, we
    // can only deal with zero value here. In the future, we need to deal with
    // the binding of non-zero value in the case of whole region.
    State = State->bindDefaultZero(svalBuilder.makeLoc(BR),
                                   C.getLocationContext());
  } else {
    // If the destination buffer's extent is not equal to the value of
    // third argument, just invalidate buffer.
    State = InvalidateBuffer(C, State, DstBuffer, MemVal,
                             /*IsSourceBuffer*/ false, Size);
  }

  if (StateNullChar && !StateNonNullChar) {
    // If the value of the second argument of 'memset()' is zero, set the
    // string length of destination buffer to 0 directly.
    State = setCStringLength(State, MR,
                             svalBuilder.makeZeroVal(Ctx.getSizeType()));
  } else if (!StateNullChar && StateNonNullChar) {
    SVal NewStrLen = svalBuilder.getMetadataSymbolVal(
        CStringChecker::getTag(), MR, DstBuffer, Ctx.getSizeType(),
        C.getLocationContext(), C.blockCount());

    // If the value of second argument is not zero, then the string length
    // is at least the size argument.
    SVal NewStrLenGESize = svalBuilder.evalBinOp(
        State, BO_GE, NewStrLen, SizeVal, svalBuilder.getConditionType());

    State = setCStringLength(
        State->assume(NewStrLenGESize.castAs<DefinedOrUnknownSVal>(), true),
        MR, NewStrLen);
  }
} else {
  // If the offset is not zero and char value is not concrete, we can do
  // nothing but invalidate the buffer.
  State = InvalidateBuffer(C, State, DstBuffer, MemVal,
                           /*IsSourceBuffer*/ false, Size);
}
return true;
1130}

1132//===----------------------------------------------------------------------===//
1133// evaluation of individual function calls.
1134//===----------------------------------------------------------------------===//

1136void CStringChecker::evalCopyCommon(CheckerContext &C,
                                  const CallExpr *CE,
                                  ProgramStateRef state,
                                  const Expr *Size, const Expr *Dest,
                                  const Expr *Source, bool Restricted,
                                  bool IsMempcpy) const {
CurrentFunctionDescription = "memory copy function";

// See if the size argument is zero.
const LocationContext *LCtx = C.getLocationContext();
SVal sizeVal = state->getSVal(Size, LCtx);
QualType sizeTy = Size->getType();

ProgramStateRef stateZeroSize, stateNonZeroSize;
std::tie(stateZeroSize, stateNonZeroSize) =
  assumeZero(C, state, sizeVal, sizeTy);

// Get the value of the Dest.
SVal destVal = state->getSVal(Dest, LCtx);

// If the size is zero, there won't be any actual memory access, so
// just bind the return value to the destination buffer and return.
if (stateZeroSize && !stateNonZeroSize) {
  stateZeroSize = stateZeroSize->BindExpr(CE, LCtx, destVal);
  C.addTransition(stateZeroSize);
  return;
}

// If the size can be nonzero, we have to check the other arguments.
if (stateNonZeroSize) {
  state = stateNonZeroSize;

  // Ensure the destination is not null. If it is NULL there will be a
  // NULL pointer dereference.
  state = checkNonNull(C, state, Dest, destVal, 1);
  if (!state)
    return;

  // Get the value of the Src.
  SVal srcVal = state->getSVal(Source, LCtx);

  // Ensure the source is not null. If it is NULL there will be a
  // NULL pointer dereference.
  state = checkNonNull(C, state, Source, srcVal, 2);
  if (!state)
    return;

  // Ensure the accesses are valid and that the buffers do not overlap.
  const char * const writeWarning =
    "Memory copy function overflows destination buffer";
  state = CheckBufferAccess(C, state, Size, Dest, Source,
                            writeWarning, /* sourceWarning = */ nullptr);
  if (Restricted)
    state = CheckOverlap(C, state, Size, Dest, Source);

  if (!state)
    return;

  // If this is mempcpy, get the byte after the last byte copied and
  // bind the expr.
  if (IsMempcpy) {
    // Get the byte after the last byte copied.
    SValBuilder &SvalBuilder = C.getSValBuilder();
    ASTContext &Ctx = SvalBuilder.getContext();
    QualType CharPtrTy = Ctx.getPointerType(Ctx.CharTy);
    SVal DestRegCharVal =
        SvalBuilder.evalCast(destVal, CharPtrTy, Dest->getType());
    SVal lastElement = C.getSValBuilder().evalBinOp(
        state, BO_Add, DestRegCharVal, sizeVal, Dest->getType());
    // If we don't know how much we copied, we can at least
    // conjure a return value for later.
    if (lastElement.isUnknown())
      lastElement = C.getSValBuilder().conjureSymbolVal(nullptr, CE, LCtx,
                                                        C.blockCount());

    // The byte after the last byte copied is the return value.
    state = state->BindExpr(CE, LCtx, lastElement);
  } else {
    // All other copies return the destination buffer.
    // (Well, bcopy() has a void return type, but this won't hurt.)
    state = state->BindExpr(CE, LCtx, destVal);
  }

  // Invalidate the destination (regular invalidation without pointer-escaping
  // the address of the top-level region).
  // FIXME: Even if we can't perfectly model the copy, we should see if we
  // can use LazyCompoundVals to copy the source values into the destination.
  // This would probably remove any existing bindings past the end of the
  // copied region, but that's still an improvement over blank invalidation.
  state = InvalidateBuffer(C, state, Dest, C.getSVal(Dest),
                           /*IsSourceBuffer*/false, Size);

  // Invalidate the source (const-invalidation without const-pointer-escaping
  // the address of the top-level region).
  state = InvalidateBuffer(C, state, Source, C.getSVal(Source),
                           /*IsSourceBuffer*/true, nullptr);

  C.addTransition(state);
}
1235}


1238void CStringChecker::evalMemcpy(CheckerContext &C, const CallExpr *CE) const {
// void *memcpy(void *restrict dst, const void *restrict src, size_t n);
// The return value is the address of the destination buffer.
const Expr *Dest = CE->getArg(0);
ProgramStateRef state = C.getState();

evalCopyCommon(C, CE, state, CE->getArg(2), Dest, CE->getArg(1), true);
1245}

1247void CStringChecker::evalMempcpy(CheckerContext &C, const CallExpr *CE) const {
// void *mempcpy(void *restrict dst, const void *restrict src, size_t n);
// The return value is a pointer to the byte following the last written byte.
const Expr *Dest = CE->getArg(0);
ProgramStateRef state = C.getState();

evalCopyCommon(C, CE, state, CE->getArg(2), Dest, CE->getArg(1), true, true);
1254}

1256void CStringChecker::evalMemmove(CheckerContext &C, const CallExpr *CE) const {
// void *memmove(void *dst, const void *src, size_t n);
// The return value is the address of the destination buffer.
const Expr *Dest = CE->getArg(0);
ProgramStateRef state = C.getState();

evalCopyCommon(C, CE, state, CE->getArg(2), Dest, CE->getArg(1));
1263}

1265void CStringChecker::evalBcopy(CheckerContext &C, const CallExpr *CE) const {
// void bcopy(const void *src, void *dst, size_t n);
evalCopyCommon(C, CE, C.getState(),
               CE->getArg(2), CE->getArg(1), CE->getArg(0));
1269}

1271void CStringChecker::evalMemcmp(CheckerContext &C, const CallExpr *CE) const {
// int memcmp(const void *s1, const void *s2, size_t n);
CurrentFunctionDescription = "memory comparison function";

const Expr *Left = CE->getArg(0);
const Expr *Right = CE->getArg(1);
const Expr *Size = CE->getArg(2);

ProgramStateRef state = C.getState();
SValBuilder &svalBuilder = C.getSValBuilder();

// See if the size argument is zero.
const LocationContext *LCtx = C.getLocationContext();
SVal sizeVal = state->getSVal(Size, LCtx);
QualType sizeTy = Size->getType();

ProgramStateRef stateZeroSize, stateNonZeroSize;
std::tie(stateZeroSize, stateNonZeroSize) =
  assumeZero(C, state, sizeVal, sizeTy);

// If the size can be zero, the result will be 0 in that case, and we don't
// have to check either of the buffers.
if (stateZeroSize) {
  state = stateZeroSize;
  state = state->BindExpr(CE, LCtx,
                          svalBuilder.makeZeroVal(CE->getType()));
  C.addTransition(state);
}

// If the size can be nonzero, we have to check the other arguments.
if (stateNonZeroSize) {
  state = stateNonZeroSize;
  // If we know the two buffers are the same, we know the result is 0.
  // First, get the two buffers' addresses. Another checker will have already
  // made sure they're not undefined.
  DefinedOrUnknownSVal LV =
      state->getSVal(Left, LCtx).castAs<DefinedOrUnknownSVal>();
  DefinedOrUnknownSVal RV =
      state->getSVal(Right, LCtx).castAs<DefinedOrUnknownSVal>();

  // See if they are the same.
  DefinedOrUnknownSVal SameBuf = svalBuilder.evalEQ(state, LV, RV);
  ProgramStateRef StSameBuf, StNotSameBuf;
  std::tie(StSameBuf, StNotSameBuf) = state->assume(SameBuf);

  // If the two arguments are the same buffer, we know the result is 0,
  // and we only need to check one size.
  if (StSameBuf && !StNotSameBuf) {
    state = StSameBuf;
    state = CheckBufferAccess(C, state, Size, Left);
    if (state) {
      state = StSameBuf->BindExpr(CE, LCtx,
                                  svalBuilder.makeZeroVal(CE->getType()));
      C.addTransition(state);
    }
    return;
  }

  // If the two arguments might be different buffers, we have to check
  // the size of both of them.
  assert(StNotSameBuf)((StNotSameBuf) ? static_cast<void> (0) : __assert_fail
 ("StNotSameBuf", "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 1331, __PRETTY_FUNCTION__));
  state = CheckBufferAccess(C, state, Size, Left, Right);
  if (state) {
    // The return value is the comparison result, which we don't know.
    SVal CmpV =
        svalBuilder.conjureSymbolVal(nullptr, CE, LCtx, C.blockCount());
    state = state->BindExpr(CE, LCtx, CmpV);
    C.addTransition(state);
  }
}
1341}

1343void CStringChecker::evalstrLength(CheckerContext &C,
                                 const CallExpr *CE) const {
// size_t strlen(const char *s);
evalstrLengthCommon(C, CE, /* IsStrnlen = */ false);
1347}

1349void CStringChecker::evalstrnLength(CheckerContext &C,
                                  const CallExpr *CE) const {
// size_t strnlen(const char *s, size_t maxlen);
evalstrLengthCommon(C, CE, /* IsStrnlen = */ true);
1353}

1355void CStringChecker::evalstrLengthCommon(CheckerContext &C, const CallExpr *CE,
                                       bool IsStrnlen) const {
CurrentFunctionDescription = "string length function";
ProgramStateRef state = C.getState();
const LocationContext *LCtx = C.getLocationContext();

if (IsStrnlen) {
  const Expr *maxlenExpr = CE->getArg(1);
  SVal maxlenVal = state->getSVal(maxlenExpr, LCtx);

  ProgramStateRef stateZeroSize, stateNonZeroSize;
  std::tie(stateZeroSize, stateNonZeroSize) =
    assumeZero(C, state, maxlenVal, maxlenExpr->getType());

  // If the size can be zero, the result will be 0 in that case, and we don't
  // have to check the string itself.
  if (stateZeroSize) {
    SVal zero = C.getSValBuilder().makeZeroVal(CE->getType());
    stateZeroSize = stateZeroSize->BindExpr(CE, LCtx, zero);
    C.addTransition(stateZeroSize);
  }

  // If the size is GUARANTEED to be zero, we're done!
  if (!stateNonZeroSize)
    return;

  // Otherwise, record the assumption that the size is nonzero.
  state = stateNonZeroSize;
}

// Check that the string argument is non-null.
const Expr *Arg = CE->getArg(0);
SVal ArgVal = state->getSVal(Arg, LCtx);

state = checkNonNull(C, state, Arg, ArgVal, 1);

if (!state)
  return;

SVal strLength = getCStringLength(C, state, Arg, ArgVal);

// If the argument isn't a valid C string, there's no valid state to
// transition to.
if (strLength.isUndef())
  return;

DefinedOrUnknownSVal result = UnknownVal();

// If the check is for strnlen() then bind the return value to no more than
// the maxlen value.
if (IsStrnlen) {
  QualType cmpTy = C.getSValBuilder().getConditionType();

  // It's a little unfortunate to be getting this again,
  // but it's not that expensive...
  const Expr *maxlenExpr = CE->getArg(1);
  SVal maxlenVal = state->getSVal(maxlenExpr, LCtx);

  Optional<NonLoc> strLengthNL = strLength.getAs<NonLoc>();
  Optional<NonLoc> maxlenValNL = maxlenVal.getAs<NonLoc>();

  if (strLengthNL && maxlenValNL) {
    ProgramStateRef stateStringTooLong, stateStringNotTooLong;

    // Check if the strLength is greater than the maxlen.
    std::tie(stateStringTooLong, stateStringNotTooLong) = state->assume(
        C.getSValBuilder()
            .evalBinOpNN(state, BO_GT, *strLengthNL, *maxlenValNL, cmpTy)
            .castAs<DefinedOrUnknownSVal>());

    if (stateStringTooLong && !stateStringNotTooLong) {
      // If the string is longer than maxlen, return maxlen.
      result = *maxlenValNL;
    } else if (stateStringNotTooLong && !stateStringTooLong) {
      // If the string is shorter than maxlen, return its length.
      result = *strLengthNL;
    }
  }

  if (result.isUnknown()) {
    // If we don't have enough information for a comparison, there's
    // no guarantee the full string length will actually be returned.
    // All we know is the return value is the min of the string length
    // and the limit. This is better than nothing.
    result = C.getSValBuilder().conjureSymbolVal(nullptr, CE, LCtx,
                                                 C.blockCount());
    NonLoc resultNL = result.castAs<NonLoc>();

    if (strLengthNL) {
      state = state->assume(C.getSValBuilder().evalBinOpNN(
                                state, BO_LE, resultNL, *strLengthNL, cmpTy)
                                .castAs<DefinedOrUnknownSVal>(), true);
    }

    if (maxlenValNL) {
      state = state->assume(C.getSValBuilder().evalBinOpNN(
                                state, BO_LE, resultNL, *maxlenValNL, cmpTy)
                                .castAs<DefinedOrUnknownSVal>(), true);
    }
  }

} else {
  // This is a plain strlen(), not strnlen().
  result = strLength.castAs<DefinedOrUnknownSVal>();

  // If we don't know the length of the string, conjure a return
  // value, so it can be used in constraints, at least.
  if (result.isUnknown()) {
    result = C.getSValBuilder().conjureSymbolVal(nullptr, CE, LCtx,
                                                 C.blockCount());
  }
}

// Bind the return value.
assert(!result.isUnknown() && "Should have conjured a value by now")((!result.isUnknown() && "Should have conjured a value by now"
) ? static_cast<void> (0) : __assert_fail ("!result.isUnknown() && \"Should have conjured a value by now\""
, "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 1469, __PRETTY_FUNCTION__));
state = state->BindExpr(CE, LCtx, result);
C.addTransition(state);
1472}

1474void CStringChecker::evalStrcpy(CheckerContext &C, const CallExpr *CE) const {
// char *strcpy(char *restrict dst, const char *restrict src);
evalStrcpyCommon(C, CE,
                 /* ReturnEnd = */ false,
                 /* IsBounded = */ false,
                 /* appendK = */ ConcatFnKind::none);
1480}

1482void CStringChecker::evalStrncpy(CheckerContext &C, const CallExpr *CE) const {
// char *strncpy(char *restrict dst, const char *restrict src, size_t n);
evalStrcpyCommon(C, CE,
                 /* ReturnEnd = */ false,
                 /* IsBounded = */ true,
                 /* appendK = */ ConcatFnKind::none);
1488}

1490void CStringChecker::evalStpcpy(CheckerContext &C, const CallExpr *CE) const {
// char *stpcpy(char *restrict dst, const char *restrict src);
evalStrcpyCommon(C, CE,
                 /* ReturnEnd = */ true,
                 /* IsBounded = */ false,
                 /* appendK = */ ConcatFnKind::none);
1496}

1498void CStringChecker::evalStrlcpy(CheckerContext &C, const CallExpr *CE) const {
// size_t strlcpy(char *dest, const char *src, size_t size);
evalStrcpyCommon(C, CE,
                 /* ReturnEnd = */ true,
                 /* IsBounded = */ true,
                 /* appendK = */ ConcatFnKind::none,
                 /* returnPtr = */ false);
1505}

1507void CStringChecker::evalStrcat(CheckerContext &C, const CallExpr *CE) const {
// char *strcat(char *restrict s1, const char *restrict s2);
evalStrcpyCommon(C, CE,
                 /* ReturnEnd = */ false,
                 /* IsBounded = */ false,
                 /* appendK = */ ConcatFnKind::strcat);
1513}

1515void CStringChecker::evalStrncat(CheckerContext &C, const CallExpr *CE) const {
//char *strncat(char *restrict s1, const char *restrict s2, size_t n);
evalStrcpyCommon(C, CE,
                 /* ReturnEnd = */ false,
                 /* IsBounded = */ true,
                 /* appendK = */ ConcatFnKind::strcat);
1521}

1523void CStringChecker::evalStrlcat(CheckerContext &C, const CallExpr *CE) const {
// size_t strlcat(char *dst, const char *src, size_t size);
// It will append at most size - strlen(dst) - 1 bytes,
// NULL-terminating the result.
evalStrcpyCommon(C, CE,
                 /* ReturnEnd = */ false,
                 /* IsBounded = */ true,
                 /* appendK = */ ConcatFnKind::strlcat,
                 /* returnPtr = */ false);
1532}

1534void CStringChecker::evalStrcpyCommon(CheckerContext &C, const CallExpr *CE,
                                    bool ReturnEnd, bool IsBounded,
                                    ConcatFnKind appendK,
                                    bool returnPtr) const {
if (appendK == ConcatFnKind::none)
  CurrentFunctionDescription = "string copy function";
else
  CurrentFunctionDescription = "string concatenation function";
ProgramStateRef state = C.getState();
const LocationContext *LCtx = C.getLocationContext();

// Check that the destination is non-null.
const Expr *Dst = CE->getArg(0);
SVal DstVal = state->getSVal(Dst, LCtx);

state = checkNonNull(C, state, Dst, DstVal, 1);
if (!state)
  return;

// Check that the source is non-null.
const Expr *srcExpr = CE->getArg(1);
SVal srcVal = state->getSVal(srcExpr, LCtx);
state = checkNonNull(C, state, srcExpr, srcVal, 2);
if (!state)
  return;

// Get the string length of the source.
SVal strLength = getCStringLength(C, state, srcExpr, srcVal);
Optional<NonLoc> strLengthNL = strLength.getAs<NonLoc>();

// Get the string length of the destination buffer.
SVal dstStrLength = getCStringLength(C, state, Dst, DstVal);
Optional<NonLoc> dstStrLengthNL = dstStrLength.getAs<NonLoc>();

// If the source isn't a valid C string, give up.
if (strLength.isUndef())
  return;

SValBuilder &svalBuilder = C.getSValBuilder();
QualType cmpTy = svalBuilder.getConditionType();
QualType sizeTy = svalBuilder.getContext().getSizeType();

// These two values allow checking two kinds of errors:
// - actual overflows caused by a source that doesn't fit in the destination
// - potential overflows caused by a bound that could exceed the destination
SVal amountCopied = UnknownVal();
SVal maxLastElementIndex = UnknownVal();
const char *boundWarning = nullptr;

state = CheckOverlap(C, state, IsBounded ? CE->getArg(2) : CE->getArg(1), Dst,
                     srcExpr);

if (!state)
  return;

// If the function is strncpy, strncat, etc... it is bounded.
if (IsBounded) {
  // Get the max number of characters to copy.
  const Expr *lenExpr = CE->getArg(2);
  SVal lenVal = state->getSVal(lenExpr, LCtx);

  // Protect against misdeclared strncpy().
  lenVal = svalBuilder.evalCast(lenVal, sizeTy, lenExpr->getType());

  Optional<NonLoc> lenValNL = lenVal.getAs<NonLoc>();

  // If we know both values, we might be able to figure out how much
  // we're copying.
  if (strLengthNL && lenValNL) {
    switch (appendK) {
    case ConcatFnKind::none:
    case ConcatFnKind::strcat: {
      ProgramStateRef stateSourceTooLong, stateSourceNotTooLong;
      // Check if the max number to copy is less than the length of the src.
      // If the bound is equal to the source length, strncpy won't null-
      // terminate the result!
      std::tie(stateSourceTooLong, stateSourceNotTooLong) = state->assume(
          svalBuilder
              .evalBinOpNN(state, BO_GE, *strLengthNL, *lenValNL, cmpTy)
              .castAs<DefinedOrUnknownSVal>());

      if (stateSourceTooLong && !stateSourceNotTooLong) {
        // Max number to copy is less than the length of the src, so the
        // actual strLength copied is the max number arg.
        state = stateSourceTooLong;
        amountCopied = lenVal;

      } else if (!stateSourceTooLong && stateSourceNotTooLong) {
        // The source buffer entirely fits in the bound.
        state = stateSourceNotTooLong;
        amountCopied = strLength;
      }
      break;
    }
    case ConcatFnKind::strlcat:
      if (!dstStrLengthNL)
        return;

      // amountCopied = min (size - dstLen - 1 , srcLen)
      SVal freeSpace = svalBuilder.evalBinOpNN(state, BO_Sub, *lenValNL,
                                               *dstStrLengthNL, sizeTy);
      if (!freeSpace.getAs<NonLoc>())
        return;
      freeSpace =
          svalBuilder.evalBinOp(state, BO_Sub, freeSpace,
                                svalBuilder.makeIntVal(1, sizeTy), sizeTy);
      Optional<NonLoc> freeSpaceNL = freeSpace.getAs<NonLoc>();

      // While unlikely, it is possible that the subtraction is
      // too complex to compute, let's check whether it succeeded.
      if (!freeSpaceNL)
        return;
      SVal hasEnoughSpace = svalBuilder.evalBinOpNN(
          state, BO_LE, *strLengthNL, *freeSpaceNL, cmpTy);

      ProgramStateRef TrueState, FalseState;
      std::tie(TrueState, FalseState) =
          state->assume(hasEnoughSpace.castAs<DefinedOrUnknownSVal>());

      // srcStrLength <= size - dstStrLength -1
      if (TrueState && !FalseState) {
        amountCopied = strLength;
      }

      // srcStrLength > size - dstStrLength -1
      if (!TrueState && FalseState) {
        amountCopied = freeSpace;
      }

      if (TrueState && FalseState)
        amountCopied = UnknownVal();
      break;
    }
  }
  // We still want to know if the bound is known to be too large.
  if (lenValNL) {
    switch (appendK) {
    case ConcatFnKind::strcat:
      // For strncat, the check is strlen(dst) + lenVal < sizeof(dst)

      // Get the string length of the destination. If the destination is
      // memory that can't have a string length, we shouldn't be copying
      // into it anyway.
      if (dstStrLength.isUndef())
        return;

      if (dstStrLengthNL) {
        maxLastElementIndex = svalBuilder.evalBinOpNN(
            state, BO_Add, *lenValNL, *dstStrLengthNL, sizeTy);

        boundWarning = "Size argument is greater than the free space in the "
                       "destination buffer";
      }
      break;
    case ConcatFnKind::none:
    case ConcatFnKind::strlcat:
      // For strncpy and strlcat, this is just checking
      //  that lenVal <= sizeof(dst).
      // (Yes, strncpy and strncat differ in how they treat termination.
      // strncat ALWAYS terminates, but strncpy doesn't.)

      // We need a special case for when the copy size is zero, in which
      // case strncpy will do no work at all. Our bounds check uses n-1
      // as the last element accessed, so n == 0 is problematic.
      ProgramStateRef StateZeroSize, StateNonZeroSize;
      std::tie(StateZeroSize, StateNonZeroSize) =
          assumeZero(C, state, *lenValNL, sizeTy);

      // If the size is known to be zero, we're done.
      if (StateZeroSize && !StateNonZeroSize) {
        if (returnPtr) {
          StateZeroSize = StateZeroSize->BindExpr(CE, LCtx, DstVal);
        } else {
          if (appendK == ConcatFnKind::none) {
            // strlcpy returns strlen(src)
            StateZeroSize = StateZeroSize->BindExpr(CE, LCtx, strLength);
          } else {
            // strlcat returns strlen(src) + strlen(dst)
            SVal retSize = svalBuilder.evalBinOp(
                state, BO_Add, strLength, dstStrLength, sizeTy);
            StateZeroSize = StateZeroSize->BindExpr(CE, LCtx, retSize);
          }
        }
        C.addTransition(StateZeroSize);
        return;
      }

      // Otherwise, go ahead and figure out the last element we'll touch.
      // We don't record the non-zero assumption here because we can't
      // be sure. We won't warn on a possible zero.
      NonLoc one = svalBuilder.makeIntVal(1, sizeTy).castAs<NonLoc>();
      maxLastElementIndex =
          svalBuilder.evalBinOpNN(state, BO_Sub, *lenValNL, one, sizeTy);
      boundWarning = "Size argument is greater than the length of the "
                     "destination buffer";
      break;
    }
  }
} else {
  // The function isn't bounded. The amount copied should match the length
  // of the source buffer.
  amountCopied = strLength;
}

assert(state)((state) ? static_cast<void> (0) : __assert_fail ("state"
, "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 1738, __PRETTY_FUNCTION__));

// This represents the number of characters copied into the destination
// buffer. (It may not actually be the strlen if the destination buffer
// is not terminated.)
SVal finalStrLength = UnknownVal();
SVal strlRetVal = UnknownVal();

if (appendK == ConcatFnKind::none && !returnPtr) {
  // strlcpy returns the sizeof(src)
  strlRetVal = strLength;
}

// If this is an appending function (strcat, strncat...) then set the
// string length to strlen(src) + strlen(dst) since the buffer will
// ultimately contain both.
if (appendK != ConcatFnKind::none) {
  // Get the string length of the destination. If the destination is memory
  // that can't have a string length, we shouldn't be copying into it anyway.
  if (dstStrLength.isUndef())
    return;

  if (appendK == ConcatFnKind::strlcat && dstStrLengthNL && strLengthNL) {
    strlRetVal = svalBuilder.evalBinOpNN(state, BO_Add, *strLengthNL,
                                         *dstStrLengthNL, sizeTy);
  }

  Optional<NonLoc> amountCopiedNL = amountCopied.getAs<NonLoc>();

  // If we know both string lengths, we might know the final string length.
  if (amountCopiedNL && dstStrLengthNL) {
    // Make sure the two lengths together don't overflow a size_t.
    state = checkAdditionOverflow(C, state, *amountCopiedNL, *dstStrLengthNL);
    if (!state)
      return;

    finalStrLength = svalBuilder.evalBinOpNN(state, BO_Add, *amountCopiedNL,
                                             *dstStrLengthNL, sizeTy);
  }

  // If we couldn't get a single value for the final string length,
  // we can at least bound it by the individual lengths.
  if (finalStrLength.isUnknown()) {
    // Try to get a "hypothetical" string length symbol, which we can later
    // set as a real value if that turns out to be the case.
    finalStrLength = getCStringLength(C, state, CE, DstVal, true);
    assert(!finalStrLength.isUndef())((!finalStrLength.isUndef()) ? static_cast<void> (0) : __assert_fail
 ("!finalStrLength.isUndef()", "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 1784, __PRETTY_FUNCTION__));

    if (Optional<NonLoc> finalStrLengthNL = finalStrLength.getAs<NonLoc>()) {
      if (amountCopiedNL && appendK == ConcatFnKind::none) {
        // we overwrite dst string with the src
        // finalStrLength >= srcStrLength
        SVal sourceInResult = svalBuilder.evalBinOpNN(
            state, BO_GE, *finalStrLengthNL, *amountCopiedNL, cmpTy);
        state = state->assume(sourceInResult.castAs<DefinedOrUnknownSVal>(),
                              true);
        if (!state)
          return;
      }

      if (dstStrLengthNL && appendK != ConcatFnKind::none) {
        // we extend the dst string with the src
        // finalStrLength >= dstStrLength
        SVal destInResult = svalBuilder.evalBinOpNN(state, BO_GE,
                                                    *finalStrLengthNL,
                                                    *dstStrLengthNL,
                                                    cmpTy);
        state =
            state->assume(destInResult.castAs<DefinedOrUnknownSVal>(), true);
        if (!state)
          return;
      }
    }
  }

} else {
  // Otherwise, this is a copy-over function (strcpy, strncpy, ...), and
  // the final string length will match the input string length.
  finalStrLength = amountCopied;
}

SVal Result;

if (returnPtr) {
  // The final result of the function will either be a pointer past the last
  // copied element, or a pointer to the start of the destination buffer.
  Result = (ReturnEnd ? UnknownVal() : DstVal);
} else {
  if (appendK == ConcatFnKind::strlcat || appendK == ConcatFnKind::none)
    //strlcpy, strlcat
    Result = strlRetVal;
  else
    Result = finalStrLength;
}

assert(state)((state) ? static_cast<void> (0) : __assert_fail ("state"
, "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 1833, __PRETTY_FUNCTION__));

// If the destination is a MemRegion, try to check for a buffer overflow and
// record the new string length.
if (Optional<loc::MemRegionVal> dstRegVal =
    DstVal.getAs<loc::MemRegionVal>()) {
  QualType ptrTy = Dst->getType();

  // If we have an exact value on a bounded copy, use that to check for
  // overflows, rather than our estimate about how much is actually copied.
  if (boundWarning) {
    if (Optional<NonLoc> maxLastNL = maxLastElementIndex.getAs<NonLoc>()) {
      SVal maxLastElement = svalBuilder.evalBinOpLN(state, BO_Add, *dstRegVal,
          *maxLastNL, ptrTy);
      state = CheckLocation(C, state, CE->getArg(2), maxLastElement,
          boundWarning);
      if (!state)
        return;
    }
  }

  // Then, if the final length is known...
  if (Optional<NonLoc> knownStrLength = finalStrLength.getAs<NonLoc>()) {
    SVal lastElement = svalBuilder.evalBinOpLN(state, BO_Add, *dstRegVal,
        *knownStrLength, ptrTy);

    // ...and we haven't checked the bound, we'll check the actual copy.
    if (!boundWarning) {
      const char * const warningMsg =
        "String copy function overflows destination buffer";
      state = CheckLocation(C, state, Dst, lastElement, warningMsg);
      if (!state)
        return;
    }

    // If this is a stpcpy-style copy, the last element is the return value.
    if (returnPtr && ReturnEnd)
      Result = lastElement;
  }

  // Invalidate the destination (regular invalidation without pointer-escaping
  // the address of the top-level region). This must happen before we set the
  // C string length because invalidation will clear the length.
  // FIXME: Even if we can't perfectly model the copy, we should see if we
  // can use LazyCompoundVals to copy the source values into the destination.
  // This would probably remove any existing bindings past the end of the
  // string, but that's still an improvement over blank invalidation.
  state = InvalidateBuffer(C, state, Dst, *dstRegVal,
      /*IsSourceBuffer*/false, nullptr);

  // Invalidate the source (const-invalidation without const-pointer-escaping
  // the address of the top-level region).
  state = InvalidateBuffer(C, state, srcExpr, srcVal, /*IsSourceBuffer*/true,
      nullptr);

  // Set the C string length of the destination, if we know it.
  if (IsBounded && (appendK == ConcatFnKind::none)) {
    // strncpy is annoying in that it doesn't guarantee to null-terminate
    // the result string. If the original string didn't fit entirely inside
    // the bound (including the null-terminator), we don't know how long the
    // result is.
    if (amountCopied != strLength)
      finalStrLength = UnknownVal();
  }
  state = setCStringLength(state, dstRegVal->getRegion(), finalStrLength);
}

assert(state)((state) ? static_cast<void> (0) : __assert_fail ("state"
, "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 1900, __PRETTY_FUNCTION__));

if (returnPtr) {
  // If this is a stpcpy-style copy, but we were unable to check for a buffer
  // overflow, we still need a result. Conjure a return value.
  if (ReturnEnd && Result.isUnknown()) {
    Result = svalBuilder.conjureSymbolVal(nullptr, CE, LCtx, C.blockCount());
  }
}
// Set the return value.
state = state->BindExpr(CE, LCtx, Result);
C.addTransition(state);
1912}

1914void CStringChecker::evalStrcmp(CheckerContext &C, const CallExpr *CE) const {
//int strcmp(const char *s1, const char *s2);
evalStrcmpCommon(C, CE, /* IsBounded = */ false, /* IgnoreCase = */ false);
1917}

1919void CStringChecker::evalStrncmp(CheckerContext &C, const CallExpr *CE) const {
//int strncmp(const char *s1, const char *s2, size_t n);
evalStrcmpCommon(C, CE, /* IsBounded = */ true, /* IgnoreCase = */ false);
1922}

1924void CStringChecker::evalStrcasecmp(CheckerContext &C,
  const CallExpr *CE) const {
//int strcasecmp(const char *s1, const char *s2);
evalStrcmpCommon(C, CE, /* IsBounded = */ false, /* IgnoreCase = */ true);
1928}

1930void CStringChecker::evalStrncasecmp(CheckerContext &C,
  const CallExpr *CE) const {
//int strncasecmp(const char *s1, const char *s2, size_t n);
evalStrcmpCommon(C, CE, /* IsBounded = */ true, /* IgnoreCase = */ true);
1
Calling 'CStringChecker::evalStrcmpCommon'→
1934}

1936void CStringChecker::evalStrcmpCommon(CheckerContext &C, const CallExpr *CE,
  bool IsBounded, bool IgnoreCase) const {
CurrentFunctionDescription = "string comparison function";
ProgramStateRef state = C.getState();
const LocationContext *LCtx = C.getLocationContext();

// Check that the first string is non-null
const Expr *s1 = CE->getArg(0);
SVal s1Val = state->getSVal(s1, LCtx);
state = checkNonNull(C, state, s1, s1Val, 1);
if (!state)
2
←
Taking false branch→
  return;

// Check that the second string is non-null.
const Expr *s2 = CE->getArg(1);
SVal s2Val = state->getSVal(s2, LCtx);
state = checkNonNull(C, state, s2, s2Val, 2);
if (!state)
3
←
Taking false branch→
  return;

// Get the string length of the first string or give up.
SVal s1Length = getCStringLength(C, state, s1, s1Val);
4
←
Calling 'CStringChecker::getCStringLength'→
if (s1Length.isUndef())
  return;

// Get the string length of the second string or give up.
SVal s2Length = getCStringLength(C, state, s2, s2Val);
if (s2Length.isUndef())
  return;

// If we know the two buffers are the same, we know the result is 0.
// First, get the two buffers' addresses. Another checker will have already
// made sure they're not undefined.
DefinedOrUnknownSVal LV = s1Val.castAs<DefinedOrUnknownSVal>();
DefinedOrUnknownSVal RV = s2Val.castAs<DefinedOrUnknownSVal>();

// See if they are the same.
SValBuilder &svalBuilder = C.getSValBuilder();
DefinedOrUnknownSVal SameBuf = svalBuilder.evalEQ(state, LV, RV);
ProgramStateRef StSameBuf, StNotSameBuf;
std::tie(StSameBuf, StNotSameBuf) = state->assume(SameBuf);

// If the two arguments might be the same buffer, we know the result is 0,
// and we only need to check one size.
if (StSameBuf) {
  StSameBuf = StSameBuf->BindExpr(CE, LCtx,
      svalBuilder.makeZeroVal(CE->getType()));
  C.addTransition(StSameBuf);

  // If the two arguments are GUARANTEED to be the same, we're done!
  if (!StNotSameBuf)
    return;
}

assert(StNotSameBuf)((StNotSameBuf) ? static_cast<void> (0) : __assert_fail
 ("StNotSameBuf", "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 1990, __PRETTY_FUNCTION__));
state = StNotSameBuf;

// At this point we can go about comparing the two buffers.
// For now, we only do this if they're both known string literals.

// Attempt to extract string literals from both expressions.
const StringLiteral *s1StrLiteral = getCStringLiteral(C, state, s1, s1Val);
const StringLiteral *s2StrLiteral = getCStringLiteral(C, state, s2, s2Val);
bool canComputeResult = false;
SVal resultVal = svalBuilder.conjureSymbolVal(nullptr, CE, LCtx,
    C.blockCount());

if (s1StrLiteral && s2StrLiteral) {
  StringRef s1StrRef = s1StrLiteral->getString();
  StringRef s2StrRef = s2StrLiteral->getString();

  if (IsBounded) {
    // Get the max number of characters to compare.
    const Expr *lenExpr = CE->getArg(2);
    SVal lenVal = state->getSVal(lenExpr, LCtx);

    // If the length is known, we can get the right substrings.
    if (const llvm::APSInt *len = svalBuilder.getKnownValue(state, lenVal)) {
      // Create substrings of each to compare the prefix.
      s1StrRef = s1StrRef.substr(0, (size_t)len->getZExtValue());
      s2StrRef = s2StrRef.substr(0, (size_t)len->getZExtValue());
      canComputeResult = true;
    }
  } else {
    // This is a normal, unbounded strcmp.
    canComputeResult = true;
  }

  if (canComputeResult) {
    // Real strcmp stops at null characters.
    size_t s1Term = s1StrRef.find('\0');
    if (s1Term != StringRef::npos)
      s1StrRef = s1StrRef.substr(0, s1Term);

    size_t s2Term = s2StrRef.find('\0');
    if (s2Term != StringRef::npos)
      s2StrRef = s2StrRef.substr(0, s2Term);

    // Use StringRef's comparison methods to compute the actual result.
    int compareRes = IgnoreCase ? s1StrRef.compare_lower(s2StrRef)
      : s1StrRef.compare(s2StrRef);

    // The strcmp function returns an integer greater than, equal to, or less
    // than zero, [c11, p7.24.4.2].
    if (compareRes == 0) {
      resultVal = svalBuilder.makeIntVal(compareRes, CE->getType());
    }
    else {
      DefinedSVal zeroVal = svalBuilder.makeIntVal(0, CE->getType());
      // Constrain strcmp's result range based on the result of StringRef's
      // comparison methods.
      BinaryOperatorKind op = (compareRes == 1) ? BO_GT : BO_LT;
      SVal compareWithZero =
        svalBuilder.evalBinOp(state, op, resultVal, zeroVal,
            svalBuilder.getConditionType());
      DefinedSVal compareWithZeroVal = compareWithZero.castAs<DefinedSVal>();
      state = state->assume(compareWithZeroVal, true);
    }
  }
}

state = state->BindExpr(CE, LCtx, resultVal);

// Record this as a possible path.
C.addTransition(state);
2061}

2063void CStringChecker::evalStrsep(CheckerContext &C, const CallExpr *CE) const {
//char *strsep(char **stringp, const char *delim);
// Sanity: does the search string parameter match the return type?
const Expr *SearchStrPtr = CE->getArg(0);
QualType CharPtrTy = SearchStrPtr->getType()->getPointeeType();
if (CharPtrTy.isNull() ||
    CE->getType().getUnqualifiedType() != CharPtrTy.getUnqualifiedType())
  return;

CurrentFunctionDescription = "strsep()";
ProgramStateRef State = C.getState();
const LocationContext *LCtx = C.getLocationContext();

// Check that the search string pointer is non-null (though it may point to
// a null string).
SVal SearchStrVal = State->getSVal(SearchStrPtr, LCtx);
State = checkNonNull(C, State, SearchStrPtr, SearchStrVal, 1);
if (!State)
  return;

// Check that the delimiter string is non-null.
const Expr *DelimStr = CE->getArg(1);
SVal DelimStrVal = State->getSVal(DelimStr, LCtx);
State = checkNonNull(C, State, DelimStr, DelimStrVal, 2);
if (!State)
  return;

SValBuilder &SVB = C.getSValBuilder();
SVal Result;
if (Optional<Loc> SearchStrLoc = SearchStrVal.getAs<Loc>()) {
  // Get the current value of the search string pointer, as a char*.
  Result = State->getSVal(*SearchStrLoc, CharPtrTy);

  // Invalidate the search string, representing the change of one delimiter
  // character to NUL.
  State = InvalidateBuffer(C, State, SearchStrPtr, Result,
      /*IsSourceBuffer*/false, nullptr);

  // Overwrite the search string pointer. The new value is either an address
  // further along in the same string, or NULL if there are no more tokens.
  State = State->bindLoc(*SearchStrLoc,
      SVB.conjureSymbolVal(getTag(),
        CE,
        LCtx,
        CharPtrTy,
        C.blockCount()),
      LCtx);
} else {
  assert(SearchStrVal.isUnknown())((SearchStrVal.isUnknown()) ? static_cast<void> (0) : __assert_fail
 ("SearchStrVal.isUnknown()", "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 2111, __PRETTY_FUNCTION__));
  // Conjure a symbolic value. It's the best we can do.
  Result = SVB.conjureSymbolVal(nullptr, CE, LCtx, C.blockCount());
}

// Set the return value, and finish.
State = State->BindExpr(CE, LCtx, Result);
C.addTransition(State);
2119}

2121// These should probably be moved into a C++ standard library checker.
2122void CStringChecker::evalStdCopy(CheckerContext &C, const CallExpr *CE) const {
evalStdCopyCommon(C, CE);
2124}

2126void CStringChecker::evalStdCopyBackward(CheckerContext &C,
  const CallExpr *CE) const {
evalStdCopyCommon(C, CE);
2129}

2131void CStringChecker::evalStdCopyCommon(CheckerContext &C,
  const CallExpr *CE) const {
if (!CE->getArg(2)->getType()->isPointerType())
  return;

ProgramStateRef State = C.getState();

const LocationContext *LCtx = C.getLocationContext();

// template <class _InputIterator, class _OutputIterator>
// _OutputIterator
// copy(_InputIterator __first, _InputIterator __last,
//        _OutputIterator __result)

// Invalidate the destination buffer
const Expr *Dst = CE->getArg(2);
SVal DstVal = State->getSVal(Dst, LCtx);
State = InvalidateBuffer(C, State, Dst, DstVal, /*IsSource=*/false,
    /*Size=*/nullptr);

SValBuilder &SVB = C.getSValBuilder();

SVal ResultVal = SVB.conjureSymbolVal(nullptr, CE, LCtx, C.blockCount());
State = State->BindExpr(CE, LCtx, ResultVal);

C.addTransition(State);
2157}

2159void CStringChecker::evalMemset(CheckerContext &C, const CallExpr *CE) const {
CurrentFunctionDescription = "memory set function";

const Expr *Mem = CE->getArg(0);
const Expr *CharE = CE->getArg(1);
const Expr *Size = CE->getArg(2);
ProgramStateRef State = C.getState();

// See if the size argument is zero.
const LocationContext *LCtx = C.getLocationContext();
SVal SizeVal = State->getSVal(Size, LCtx);
QualType SizeTy = Size->getType();

ProgramStateRef StateZeroSize, StateNonZeroSize;
std::tie(StateZeroSize, StateNonZeroSize) =
  assumeZero(C, State, SizeVal, SizeTy);

// Get the value of the memory area.
SVal MemVal = State->getSVal(Mem, LCtx);

// If the size is zero, there won't be any actual memory access, so
// just bind the return value to the Mem buffer and return.
if (StateZeroSize && !StateNonZeroSize) {
  StateZeroSize = StateZeroSize->BindExpr(CE, LCtx, MemVal);
  C.addTransition(StateZeroSize);
  return;
}

// Ensure the memory area is not null.
// If it is NULL there will be a NULL pointer dereference.
State = checkNonNull(C, StateNonZeroSize, Mem, MemVal, 1);
if (!State)
  return;

State = CheckBufferAccess(C, State, Size, Mem);
if (!State)
  return;

// According to the values of the arguments, bind the value of the second
// argument to the destination buffer and set string length, or just
// invalidate the destination buffer.
if (!memsetAux(Mem, C.getSVal(CharE), Size, C, State))
  return;

State = State->BindExpr(CE, LCtx, MemVal);
C.addTransition(State);
2205}

2207void CStringChecker::evalBzero(CheckerContext &C, const CallExpr *CE) const {
CurrentFunctionDescription = "memory clearance function";

const Expr *Mem = CE->getArg(0);
const Expr *Size = CE->getArg(1);
SVal Zero = C.getSValBuilder().makeZeroVal(C.getASTContext().IntTy);

ProgramStateRef State = C.getState();

// See if the size argument is zero.
SVal SizeVal = C.getSVal(Size);
QualType SizeTy = Size->getType();

ProgramStateRef StateZeroSize, StateNonZeroSize;
std::tie(StateZeroSize, StateNonZeroSize) =
  assumeZero(C, State, SizeVal, SizeTy);

// If the size is zero, there won't be any actual memory access,
// In this case we just return.
if (StateZeroSize && !StateNonZeroSize) {
  C.addTransition(StateZeroSize);
  return;
}

// Get the value of the memory area.
SVal MemVal = C.getSVal(Mem);

// Ensure the memory area is not null.
// If it is NULL there will be a NULL pointer dereference.
State = checkNonNull(C, StateNonZeroSize, Mem, MemVal, 1);
if (!State)
  return;

State = CheckBufferAccess(C, State, Size, Mem);
if (!State)
  return;

if (!memsetAux(Mem, Zero, Size, C, State))
  return;

C.addTransition(State);
2248}

2250//===----------------------------------------------------------------------===//
2251// The driver method, and other Checker callbacks.
2252//===----------------------------------------------------------------------===//

2254CStringChecker::FnCheck CStringChecker::identifyCall(const CallEvent &Call,
                                                   CheckerContext &C) const {
const auto *CE = dyn_cast_or_null<CallExpr>(Call.getOriginExpr());
if (!CE)
  return nullptr;

const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(Call.getDecl());
if (!FD)
  return nullptr;

if (Call.isCalled(StdCopy)) {
  return &CStringChecker::evalStdCopy;
} else if (Call.isCalled(StdCopyBackward)) {
  return &CStringChecker::evalStdCopyBackward;
}

// Pro-actively check that argument types are safe to do arithmetic upon.
// We do not want to crash if someone accidentally passes a structure
// into, say, a C++ overload of any of these functions. We could not check
// that for std::copy because they may have arguments of other types.
for (auto I : CE->arguments()) {
  QualType T = I->getType();
  if (!T->isIntegralOrEnumerationType() && !T->isPointerType())
    return nullptr;
}

const FnCheck *Callback = Callbacks.lookup(Call);
if (Callback)
  return *Callback;

return nullptr;
2285}

2287bool CStringChecker::evalCall(const CallEvent &Call, CheckerContext &C) const {
FnCheck Callback = identifyCall(Call, C);

// If the callee isn't a string function, let another checker handle it.
if (!Callback)
  return false;

// Check and evaluate the call.
const auto *CE = cast<CallExpr>(Call.getOriginExpr());
(this->*Callback)(C, CE);

// If the evaluate call resulted in no change, chain to the next eval call
// handler.
// Note, the custom CString evaluation calls assume that basic safety
// properties are held. However, if the user chooses to turn off some of these
// checks, we ignore the issues and leave the call evaluation to a generic
// handler.
return C.isDifferent();
2305}

2307void CStringChecker::checkPreStmt(const DeclStmt *DS, CheckerContext &C) const {
// Record string length for char a[] = "abc";
ProgramStateRef state = C.getState();

for (const auto *I : DS->decls()) {
  const VarDecl *D = dyn_cast<VarDecl>(I);
  if (!D)
    continue;

  // FIXME: Handle array fields of structs.
  if (!D->getType()->isArrayType())
    continue;

  const Expr *Init = D->getInit();
  if (!Init)
    continue;
  if (!isa<StringLiteral>(Init))
    continue;

  Loc VarLoc = state->getLValue(D, C.getLocationContext());
  const MemRegion *MR = VarLoc.getAsRegion();
  if (!MR)
    continue;

  SVal StrVal = C.getSVal(Init);
  assert(StrVal.isValid() && "Initializer string is unknown or undefined")((StrVal.isValid() && "Initializer string is unknown or undefined"
) ? static_cast<void> (0) : __assert_fail ("StrVal.isValid() && \"Initializer string is unknown or undefined\""
, "/build/llvm-toolchain-snapshot-10~++20200111100615+a1f16998f37/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp"
, 2332, __PRETTY_FUNCTION__));
  DefinedOrUnknownSVal strLength =
    getCStringLength(C, state, Init, StrVal).castAs<DefinedOrUnknownSVal>();

  state = state->set<CStringLength>(MR, strLength);
}

C.addTransition(state);
2340}

2342ProgramStateRef
2343CStringChecker::checkRegionChanges(ProgramStateRef state,
  const InvalidatedSymbols *,
  ArrayRef<const MemRegion *> ExplicitRegions,
  ArrayRef<const MemRegion *> Regions,
  const LocationContext *LCtx,
  const CallEvent *Call) const {
CStringLengthTy Entries = state->get<CStringLength>();
if (Entries.isEmpty())
  return state;

llvm::SmallPtrSet<const MemRegion *, 8> Invalidated;
llvm::SmallPtrSet<const MemRegion *, 32> SuperRegions;

// First build sets for the changed regions and their super-regions.
for (ArrayRef<const MemRegion *>::iterator
    I = Regions.begin(), E = Regions.end(); I != E; ++I) {
  const MemRegion *MR = *I;
  Invalidated.insert(MR);

  SuperRegions.insert(MR);
  while (const SubRegion *SR = dyn_cast<SubRegion>(MR)) {
    MR = SR->getSuperRegion();
    SuperRegions.insert(MR);
  }
}

CStringLengthTy::Factory &F = state->get_context<CStringLength>();

// Then loop over the entries in the current state.
for (CStringLengthTy::iterator I = Entries.begin(),
    E = Entries.end(); I != E; ++I) {
  const MemRegion *MR = I.getKey();

  // Is this entry for a super-region of a changed region?
  if (SuperRegions.count(MR)) {
    Entries = F.remove(Entries, MR);
    continue;
  }

  // Is this entry for a sub-region of a changed region?
  const MemRegion *Super = MR;
  while (const SubRegion *SR = dyn_cast<SubRegion>(Super)) {
    Super = SR->getSuperRegion();
    if (Invalidated.count(Super)) {
      Entries = F.remove(Entries, MR);
      break;
    }
  }
}

return state->set<CStringLength>(Entries);
2394}

2396void CStringChecker::checkLiveSymbols(ProgramStateRef state,
  SymbolReaper &SR) const {
// Mark all symbols in our string length map as valid.
CStringLengthTy Entries = state->get<CStringLength>();

for (CStringLengthTy::iterator I = Entries.begin(), E = Entries.end();
    I != E; ++I) {
  SVal Len = I.getData();

  for (SymExpr::symbol_iterator si = Len.symbol_begin(),
      se = Len.symbol_end(); si != se; ++si)
    SR.markInUse(*si);
}
2409}

2411void CStringChecker::checkDeadSymbols(SymbolReaper &SR,
  CheckerContext &C) const {
ProgramStateRef state = C.getState();
CStringLengthTy Entries = state->get<CStringLength>();
if (Entries.isEmpty())
  return;

CStringLengthTy::Factory &F = state->get_context<CStringLength>();
for (CStringLengthTy::iterator I = Entries.begin(), E = Entries.end();
    I != E; ++I) {
  SVal Len = I.getData();
  if (SymbolRef Sym = Len.getAsSymbol()) {
    if (SR.isDead(Sym))
      Entries = F.remove(Entries, I.getKey());
  }
}

state = state->set<CStringLength>(Entries);
C.addTransition(state);
2430}

2432void ento::registerCStringModeling(CheckerManager &Mgr) {
Mgr.registerChecker<CStringChecker>();
2434}

2436bool ento::shouldRegisterCStringModeling(const LangOptions &LO) {
return true;
2438}

2440#define REGISTER_CHECKER(name)void ento::registername(CheckerManager &mgr) { CStringChecker
 *checker = mgr.getChecker<CStringChecker>(); checker->
Filter.Checkname = true; checker->Filter.CheckNamename = mgr
.getCurrentCheckerName(); } bool ento::shouldRegistername(const
 LangOptions &LO) { return true; }                                                 \
void ento::register##name(CheckerManager &mgr) {                             \
  CStringChecker *checker = mgr.getChecker<CStringChecker>();                \
  checker->Filter.Check##name = true;                                        \
  checker->Filter.CheckName##name = mgr.getCurrentCheckerName();             \
}                                                                            \
                                                                             \
bool ento::shouldRegister##name(const LangOptions &LO) { return true; }

2449REGISTER_CHECKER(CStringNullArg)void ento::registerCStringNullArg(CheckerManager &mgr) { CStringChecker
 *checker = mgr.getChecker<CStringChecker>(); checker->
Filter.CheckCStringNullArg = true; checker->Filter.CheckNameCStringNullArg
 = mgr.getCurrentCheckerName(); } bool ento::shouldRegisterCStringNullArg
(const LangOptions &LO) { return true; }
2450REGISTER_CHECKER(CStringOutOfBounds)void ento::registerCStringOutOfBounds(CheckerManager &mgr
) { CStringChecker *checker = mgr.getChecker<CStringChecker
>(); checker->Filter.CheckCStringOutOfBounds = true; checker
->Filter.CheckNameCStringOutOfBounds = mgr.getCurrentCheckerName
(); } bool ento::shouldRegisterCStringOutOfBounds(const LangOptions
 &LO) { return true; }
2451REGISTER_CHECKER(CStringBufferOverlap)void ento::registerCStringBufferOverlap(CheckerManager &mgr
) { CStringChecker *checker = mgr.getChecker<CStringChecker
>(); checker->Filter.CheckCStringBufferOverlap = true; checker
->Filter.CheckNameCStringBufferOverlap = mgr.getCurrentCheckerName
(); } bool ento::shouldRegisterCStringBufferOverlap(const LangOptions
 &LO) { return true; }
2452REGISTER_CHECKER(CStringNotNullTerm)void ento::registerCStringNotNullTerm(CheckerManager &mgr
) { CStringChecker *checker = mgr.getChecker<CStringChecker
>(); checker->Filter.CheckCStringNotNullTerm = true; checker
->Filter.CheckNameCStringNotNullTerm = mgr.getCurrentCheckerName
(); } bool ento::shouldRegisterCStringNotNullTerm(const LangOptions
 &LO) { return true; }