Bug Summary

File:tools/clang/lib/CodeGen/CGObjCRuntime.cpp
Warning:line 111, column 58
Access to field 'StorageSize' results in a dereference of a null pointer (loaded from variable 'Info')

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 CGObjCRuntime.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 -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mthread-model posix -relaxed-aliasing -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -momit-leaf-frame-pointer -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-9/lib/clang/9.0.0 -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-9~svn358520/build-llvm/tools/clang/lib/CodeGen -I /build/llvm-toolchain-snapshot-9~svn358520/tools/clang/lib/CodeGen -I /build/llvm-toolchain-snapshot-9~svn358520/tools/clang/include -I /build/llvm-toolchain-snapshot-9~svn358520/build-llvm/tools/clang/include -I /build/llvm-toolchain-snapshot-9~svn358520/build-llvm/include -I /build/llvm-toolchain-snapshot-9~svn358520/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/include/clang/9.0.0/include/ -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-9/lib/clang/9.0.0/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++11 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-9~svn358520/build-llvm/tools/clang/lib/CodeGen -fdebug-prefix-map=/build/llvm-toolchain-snapshot-9~svn358520=. -ferror-limit 19 -fmessage-length 0 -fvisibility-inlines-hidden -stack-protector 2 -fobjc-runtime=gcc -fno-common -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -o /tmp/scan-build-2019-04-17-050842-1547-1 -x c++ /build/llvm-toolchain-snapshot-9~svn358520/tools/clang/lib/CodeGen/CGObjCRuntime.cpp -faddrsig
1//==- CGObjCRuntime.cpp - Interface to Shared Objective-C Runtime Features ==//
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 abstract class defines the interface for Objective-C runtime-specific
10// code generation. It provides some concrete helper methods for functionality
11// shared between all (or most) of the Objective-C runtimes supported by clang.
12//
13//===----------------------------------------------------------------------===//
14
15#include "CGObjCRuntime.h"
16#include "CGCleanup.h"
17#include "CGCXXABI.h"
18#include "CGRecordLayout.h"
19#include "CodeGenFunction.h"
20#include "CodeGenModule.h"
21#include "clang/AST/RecordLayout.h"
22#include "clang/AST/StmtObjC.h"
23#include "clang/CodeGen/CGFunctionInfo.h"
24#include "llvm/Support/SaveAndRestore.h"
25
26using namespace clang;
27using namespace CodeGen;
28
29uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM,
30 const ObjCInterfaceDecl *OID,
31 const ObjCIvarDecl *Ivar) {
32 return CGM.getContext().lookupFieldBitOffset(OID, nullptr, Ivar) /
33 CGM.getContext().getCharWidth();
34}
35
36uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM,
37 const ObjCImplementationDecl *OID,
38 const ObjCIvarDecl *Ivar) {
39 return CGM.getContext().lookupFieldBitOffset(OID->getClassInterface(), OID,
40 Ivar) /
41 CGM.getContext().getCharWidth();
42}
43
44unsigned CGObjCRuntime::ComputeBitfieldBitOffset(
45 CodeGen::CodeGenModule &CGM,
46 const ObjCInterfaceDecl *ID,
47 const ObjCIvarDecl *Ivar) {
48 return CGM.getContext().lookupFieldBitOffset(ID, ID->getImplementation(),
49 Ivar);
50}
51
52LValue CGObjCRuntime::EmitValueForIvarAtOffset(CodeGen::CodeGenFunction &CGF,
53 const ObjCInterfaceDecl *OID,
54 llvm::Value *BaseValue,
55 const ObjCIvarDecl *Ivar,
56 unsigned CVRQualifiers,
57 llvm::Value *Offset) {
58 // Compute (type*) ( (char *) BaseValue + Offset)
59 QualType InterfaceTy{OID->getTypeForDecl(), 0};
60 QualType ObjectPtrTy =
61 CGF.CGM.getContext().getObjCObjectPointerType(InterfaceTy);
62 QualType IvarTy =
63 Ivar->getUsageType(ObjectPtrTy).withCVRQualifiers(CVRQualifiers);
64 llvm::Type *LTy = CGF.CGM.getTypes().ConvertTypeForMem(IvarTy);
65 llvm::Value *V = CGF.Builder.CreateBitCast(BaseValue, CGF.Int8PtrTy);
66 V = CGF.Builder.CreateInBoundsGEP(V, Offset, "add.ptr");
67
68 if (!Ivar->isBitField()) {
1
Assuming the condition is false
2
Taking false branch
69 V = CGF.Builder.CreateBitCast(V, llvm::PointerType::getUnqual(LTy));
70 LValue LV = CGF.MakeNaturalAlignAddrLValue(V, IvarTy);
71 return LV;
72 }
73
74 // We need to compute an access strategy for this bit-field. We are given the
75 // offset to the first byte in the bit-field, the sub-byte offset is taken
76 // from the original layout. We reuse the normal bit-field access strategy by
77 // treating this as an access to a struct where the bit-field is in byte 0,
78 // and adjust the containing type size as appropriate.
79 //
80 // FIXME: Note that currently we make a very conservative estimate of the
81 // alignment of the bit-field, because (a) it is not clear what guarantees the
82 // runtime makes us, and (b) we don't have a way to specify that the struct is
83 // at an alignment plus offset.
84 //
85 // Note, there is a subtle invariant here: we can only call this routine on
86 // non-synthesized ivars but we may be called for synthesized ivars. However,
87 // a synthesized ivar can never be a bit-field, so this is safe.
88 uint64_t FieldBitOffset =
89 CGF.CGM.getContext().lookupFieldBitOffset(OID, nullptr, Ivar);
90 uint64_t BitOffset = FieldBitOffset % CGF.CGM.getContext().getCharWidth();
91 uint64_t AlignmentBits = CGF.CGM.getTarget().getCharAlign();
92 uint64_t BitFieldSize = Ivar->getBitWidthValue(CGF.getContext());
93 CharUnits StorageSize = CGF.CGM.getContext().toCharUnitsFromBits(
94 llvm::alignTo(BitOffset + BitFieldSize, AlignmentBits));
95 CharUnits Alignment = CGF.CGM.getContext().toCharUnitsFromBits(AlignmentBits);
96
97 // Allocate a new CGBitFieldInfo object to describe this access.
98 //
99 // FIXME: This is incredibly wasteful, these should be uniqued or part of some
100 // layout object. However, this is blocked on other cleanups to the
101 // Objective-C code, so for now we just live with allocating a bunch of these
102 // objects.
103 CGBitFieldInfo *Info = new (CGF.CGM.getContext()) CGBitFieldInfo(
3
'Info' initialized to a null pointer value
104 CGBitFieldInfo::MakeInfo(CGF.CGM.getTypes(), Ivar, BitOffset, BitFieldSize,
105 CGF.CGM.getContext().toBits(StorageSize),
106 CharUnits::fromQuantity(0)));
107
108 Address Addr(V, Alignment);
109 Addr = CGF.Builder.CreateElementBitCast(Addr,
110 llvm::Type::getIntNTy(CGF.getLLVMContext(),
111 Info->StorageSize));
4
Access to field 'StorageSize' results in a dereference of a null pointer (loaded from variable 'Info')
112 return LValue::MakeBitfield(Addr, *Info, IvarTy,
113 LValueBaseInfo(AlignmentSource::Decl),
114 TBAAAccessInfo());
115}
116
117namespace {
118 struct CatchHandler {
119 const VarDecl *Variable;
120 const Stmt *Body;
121 llvm::BasicBlock *Block;
122 llvm::Constant *TypeInfo;
123 /// Flags used to differentiate cleanups and catchalls in Windows SEH
124 unsigned Flags;
125 };
126
127 struct CallObjCEndCatch final : EHScopeStack::Cleanup {
128 CallObjCEndCatch(bool MightThrow, llvm::FunctionCallee Fn)
129 : MightThrow(MightThrow), Fn(Fn) {}
130 bool MightThrow;
131 llvm::FunctionCallee Fn;
132
133 void Emit(CodeGenFunction &CGF, Flags flags) override {
134 if (MightThrow)
135 CGF.EmitRuntimeCallOrInvoke(Fn);
136 else
137 CGF.EmitNounwindRuntimeCall(Fn);
138 }
139 };
140}
141
142void CGObjCRuntime::EmitTryCatchStmt(CodeGenFunction &CGF,
143 const ObjCAtTryStmt &S,
144 llvm::FunctionCallee beginCatchFn,
145 llvm::FunctionCallee endCatchFn,
146 llvm::FunctionCallee exceptionRethrowFn) {
147 // Jump destination for falling out of catch bodies.
148 CodeGenFunction::JumpDest Cont;
149 if (S.getNumCatchStmts())
150 Cont = CGF.getJumpDestInCurrentScope("eh.cont");
151
152 bool useFunclets = EHPersonality::get(CGF).usesFuncletPads();
153
154 CodeGenFunction::FinallyInfo FinallyInfo;
155 if (!useFunclets)
156 if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt())
157 FinallyInfo.enter(CGF, Finally->getFinallyBody(),
158 beginCatchFn, endCatchFn, exceptionRethrowFn);
159
160 SmallVector<CatchHandler, 8> Handlers;
161
162
163 // Enter the catch, if there is one.
164 if (S.getNumCatchStmts()) {
165 for (unsigned I = 0, N = S.getNumCatchStmts(); I != N; ++I) {
166 const ObjCAtCatchStmt *CatchStmt = S.getCatchStmt(I);
167 const VarDecl *CatchDecl = CatchStmt->getCatchParamDecl();
168
169 Handlers.push_back(CatchHandler());
170 CatchHandler &Handler = Handlers.back();
171 Handler.Variable = CatchDecl;
172 Handler.Body = CatchStmt->getCatchBody();
173 Handler.Block = CGF.createBasicBlock("catch");
174 Handler.Flags = 0;
175
176 // @catch(...) always matches.
177 if (!CatchDecl) {
178 auto catchAll = getCatchAllTypeInfo();
179 Handler.TypeInfo = catchAll.RTTI;
180 Handler.Flags = catchAll.Flags;
181 // Don't consider any other catches.
182 break;
183 }
184
185 Handler.TypeInfo = GetEHType(CatchDecl->getType());
186 }
187
188 EHCatchScope *Catch = CGF.EHStack.pushCatch(Handlers.size());
189 for (unsigned I = 0, E = Handlers.size(); I != E; ++I)
190 Catch->setHandler(I, { Handlers[I].TypeInfo, Handlers[I].Flags }, Handlers[I].Block);
191 }
192
193 if (useFunclets)
194 if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt()) {
195 CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true);
196 if (!CGF.CurSEHParent)
197 CGF.CurSEHParent = cast<NamedDecl>(CGF.CurFuncDecl);
198 // Outline the finally block.
199 const Stmt *FinallyBlock = Finally->getFinallyBody();
200 HelperCGF.startOutlinedSEHHelper(CGF, /*isFilter*/false, FinallyBlock);
201
202 // Emit the original filter expression, convert to i32, and return.
203 HelperCGF.EmitStmt(FinallyBlock);
204
205 HelperCGF.FinishFunction(FinallyBlock->getEndLoc());
206
207 llvm::Function *FinallyFunc = HelperCGF.CurFn;
208
209
210 // Push a cleanup for __finally blocks.
211 CGF.pushSEHCleanup(NormalAndEHCleanup, FinallyFunc);
212 }
213
214
215 // Emit the try body.
216 CGF.EmitStmt(S.getTryBody());
217
218 // Leave the try.
219 if (S.getNumCatchStmts())
220 CGF.popCatchScope();
221
222 // Remember where we were.
223 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP();
224
225 // Emit the handlers.
226 for (unsigned I = 0, E = Handlers.size(); I != E; ++I) {
227 CatchHandler &Handler = Handlers[I];
228
229 CGF.EmitBlock(Handler.Block);
230 llvm::CatchPadInst *CPI = nullptr;
231 SaveAndRestore<llvm::Instruction *> RestoreCurrentFuncletPad(CGF.CurrentFuncletPad);
232 if (useFunclets)
233 if ((CPI = dyn_cast_or_null<llvm::CatchPadInst>(Handler.Block->getFirstNonPHI()))) {
234 CGF.CurrentFuncletPad = CPI;
235 CPI->setOperand(2, CGF.getExceptionSlot().getPointer());
236 }
237 llvm::Value *RawExn = CGF.getExceptionFromSlot();
238
239 // Enter the catch.
240 llvm::Value *Exn = RawExn;
241 if (beginCatchFn)
242 Exn = CGF.EmitNounwindRuntimeCall(beginCatchFn, RawExn, "exn.adjusted");
243
244 CodeGenFunction::LexicalScope cleanups(CGF, Handler.Body->getSourceRange());
245
246 if (endCatchFn) {
247 // Add a cleanup to leave the catch.
248 bool EndCatchMightThrow = (Handler.Variable == nullptr);
249
250 CGF.EHStack.pushCleanup<CallObjCEndCatch>(NormalAndEHCleanup,
251 EndCatchMightThrow,
252 endCatchFn);
253 }
254
255 // Bind the catch parameter if it exists.
256 if (const VarDecl *CatchParam = Handler.Variable) {
257 llvm::Type *CatchType = CGF.ConvertType(CatchParam->getType());
258 llvm::Value *CastExn = CGF.Builder.CreateBitCast(Exn, CatchType);
259
260 CGF.EmitAutoVarDecl(*CatchParam);
261 EmitInitOfCatchParam(CGF, CastExn, CatchParam);
262 }
263 if (CPI)
264 CGF.EHStack.pushCleanup<CatchRetScope>(NormalCleanup, CPI);
265
266 CGF.ObjCEHValueStack.push_back(Exn);
267 CGF.EmitStmt(Handler.Body);
268 CGF.ObjCEHValueStack.pop_back();
269
270 // Leave any cleanups associated with the catch.
271 cleanups.ForceCleanup();
272
273 CGF.EmitBranchThroughCleanup(Cont);
274 }
275
276 // Go back to the try-statement fallthrough.
277 CGF.Builder.restoreIP(SavedIP);
278
279 // Pop out of the finally.
280 if (!useFunclets && S.getFinallyStmt())
281 FinallyInfo.exit(CGF);
282
283 if (Cont.isValid())
284 CGF.EmitBlock(Cont.getBlock());
285}
286
287void CGObjCRuntime::EmitInitOfCatchParam(CodeGenFunction &CGF,
288 llvm::Value *exn,
289 const VarDecl *paramDecl) {
290
291 Address paramAddr = CGF.GetAddrOfLocalVar(paramDecl);
292
293 switch (paramDecl->getType().getQualifiers().getObjCLifetime()) {
294 case Qualifiers::OCL_Strong:
295 exn = CGF.EmitARCRetainNonBlock(exn);
296 LLVM_FALLTHROUGH[[clang::fallthrough]];
297
298 case Qualifiers::OCL_None:
299 case Qualifiers::OCL_ExplicitNone:
300 case Qualifiers::OCL_Autoreleasing:
301 CGF.Builder.CreateStore(exn, paramAddr);
302 return;
303
304 case Qualifiers::OCL_Weak:
305 CGF.EmitARCInitWeak(paramAddr, exn);
306 return;
307 }
308 llvm_unreachable("invalid ownership qualifier")::llvm::llvm_unreachable_internal("invalid ownership qualifier"
, "/build/llvm-toolchain-snapshot-9~svn358520/tools/clang/lib/CodeGen/CGObjCRuntime.cpp"
, 308)
;
309}
310
311namespace {
312 struct CallSyncExit final : EHScopeStack::Cleanup {
313 llvm::FunctionCallee SyncExitFn;
314 llvm::Value *SyncArg;
315 CallSyncExit(llvm::FunctionCallee SyncExitFn, llvm::Value *SyncArg)
316 : SyncExitFn(SyncExitFn), SyncArg(SyncArg) {}
317
318 void Emit(CodeGenFunction &CGF, Flags flags) override {
319 CGF.EmitNounwindRuntimeCall(SyncExitFn, SyncArg);
320 }
321 };
322}
323
324void CGObjCRuntime::EmitAtSynchronizedStmt(CodeGenFunction &CGF,
325 const ObjCAtSynchronizedStmt &S,
326 llvm::FunctionCallee syncEnterFn,
327 llvm::FunctionCallee syncExitFn) {
328 CodeGenFunction::RunCleanupsScope cleanups(CGF);
329
330 // Evaluate the lock operand. This is guaranteed to dominate the
331 // ARC release and lock-release cleanups.
332 const Expr *lockExpr = S.getSynchExpr();
333 llvm::Value *lock;
334 if (CGF.getLangOpts().ObjCAutoRefCount) {
335 lock = CGF.EmitARCRetainScalarExpr(lockExpr);
336 lock = CGF.EmitObjCConsumeObject(lockExpr->getType(), lock);
337 } else {
338 lock = CGF.EmitScalarExpr(lockExpr);
339 }
340 lock = CGF.Builder.CreateBitCast(lock, CGF.VoidPtrTy);
341
342 // Acquire the lock.
343 CGF.Builder.CreateCall(syncEnterFn, lock)->setDoesNotThrow();
344
345 // Register an all-paths cleanup to release the lock.
346 CGF.EHStack.pushCleanup<CallSyncExit>(NormalAndEHCleanup, syncExitFn, lock);
347
348 // Emit the body of the statement.
349 CGF.EmitStmt(S.getSynchBody());
350}
351
352/// Compute the pointer-to-function type to which a message send
353/// should be casted in order to correctly call the given method
354/// with the given arguments.
355///
356/// \param method - may be null
357/// \param resultType - the result type to use if there's no method
358/// \param callArgs - the actual arguments, including implicit ones
359CGObjCRuntime::MessageSendInfo
360CGObjCRuntime::getMessageSendInfo(const ObjCMethodDecl *method,
361 QualType resultType,
362 CallArgList &callArgs) {
363 // If there's a method, use information from that.
364 if (method) {
365 const CGFunctionInfo &signature =
366 CGM.getTypes().arrangeObjCMessageSendSignature(method, callArgs[0].Ty);
367
368 llvm::PointerType *signatureType =
369 CGM.getTypes().GetFunctionType(signature)->getPointerTo();
370
371 const CGFunctionInfo &signatureForCall =
372 CGM.getTypes().arrangeCall(signature, callArgs);
373
374 return MessageSendInfo(signatureForCall, signatureType);
375 }
376
377 // There's no method; just use a default CC.
378 const CGFunctionInfo &argsInfo =
379 CGM.getTypes().arrangeUnprototypedObjCMessageSend(resultType, callArgs);
380
381 // Derive the signature to call from that.
382 llvm::PointerType *signatureType =
383 CGM.getTypes().GetFunctionType(argsInfo)->getPointerTo();
384 return MessageSendInfo(argsInfo, signatureType);
385}