Bug Summary

File:llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp
Warning:line 265, column 5
Value stored to 'Value0' is never read

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 DWARFDebugLoc.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 -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 _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/build-llvm/lib/DebugInfo/DWARF -I /build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/lib/DebugInfo/DWARF -I /build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/build-llvm/include -I /build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/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~++20200112100611+7fa5290d5bd/build-llvm/lib/DebugInfo/DWARF -fdebug-prefix-map=/build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd=. -ferror-limit 19 -fmessage-length 0 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -fobjc-runtime=gcc -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -o /tmp/scan-build-2020-01-13-084841-49055-1 -x c++ /build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp
1//===- DWARFDebugLoc.cpp --------------------------------------------------===//
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#include "llvm/DebugInfo/DWARF/DWARFDebugLoc.h"
10#include "llvm/ADT/StringRef.h"
11#include "llvm/BinaryFormat/Dwarf.h"
12#include "llvm/DebugInfo/DWARF/DWARFContext.h"
13#include "llvm/DebugInfo/DWARF/DWARFExpression.h"
14#include "llvm/DebugInfo/DWARF/DWARFRelocMap.h"
15#include "llvm/DebugInfo/DWARF/DWARFUnit.h"
16#include "llvm/Support/Compiler.h"
17#include "llvm/Support/Format.h"
18#include "llvm/Support/WithColor.h"
19#include "llvm/Support/raw_ostream.h"
20#include <algorithm>
21#include <cinttypes>
22#include <cstdint>
23
24using namespace llvm;
25using object::SectionedAddress;
26
27namespace {
28class DWARFLocationInterpreter {
29 Optional<object::SectionedAddress> Base;
30 std::function<Optional<object::SectionedAddress>(uint32_t)> LookupAddr;
31
32public:
33 DWARFLocationInterpreter(
34 Optional<object::SectionedAddress> Base,
35 std::function<Optional<object::SectionedAddress>(uint32_t)> LookupAddr)
36 : Base(Base), LookupAddr(std::move(LookupAddr)) {}
37
38 Expected<Optional<DWARFLocationExpression>>
39 Interpret(const DWARFLocationEntry &E);
40};
41} // namespace
42
43static Error createResolverError(uint32_t Index, unsigned Kind) {
44 return createStringError(errc::invalid_argument,
45 "Unable to resolve indirect address %u for: %s",
46 Index, dwarf::LocListEncodingString(Kind).data());
47}
48
49Expected<Optional<DWARFLocationExpression>>
50DWARFLocationInterpreter::Interpret(const DWARFLocationEntry &E) {
51 switch (E.Kind) {
52 case dwarf::DW_LLE_end_of_list:
53 return None;
54 case dwarf::DW_LLE_base_addressx: {
55 Base = LookupAddr(E.Value0);
56 if (!Base)
57 return createResolverError(E.Value0, E.Kind);
58 return None;
59 }
60 case dwarf::DW_LLE_startx_endx: {
61 Optional<SectionedAddress> LowPC = LookupAddr(E.Value0);
62 if (!LowPC)
63 return createResolverError(E.Value0, E.Kind);
64 Optional<SectionedAddress> HighPC = LookupAddr(E.Value1);
65 if (!HighPC)
66 return createResolverError(E.Value1, E.Kind);
67 return DWARFLocationExpression{
68 DWARFAddressRange{LowPC->Address, HighPC->Address, LowPC->SectionIndex},
69 E.Loc};
70 }
71 case dwarf::DW_LLE_startx_length: {
72 Optional<SectionedAddress> LowPC = LookupAddr(E.Value0);
73 if (!LowPC)
74 return createResolverError(E.Value0, E.Kind);
75 return DWARFLocationExpression{DWARFAddressRange{LowPC->Address,
76 LowPC->Address + E.Value1,
77 LowPC->SectionIndex},
78 E.Loc};
79 }
80 case dwarf::DW_LLE_offset_pair: {
81 if (!Base) {
82 return createStringError(inconvertibleErrorCode(),
83 "Unable to resolve location list offset pair: "
84 "Base address not defined");
85 }
86 DWARFAddressRange Range{Base->Address + E.Value0, Base->Address + E.Value1,
87 Base->SectionIndex};
88 if (Range.SectionIndex == SectionedAddress::UndefSection)
89 Range.SectionIndex = E.SectionIndex;
90 return DWARFLocationExpression{Range, E.Loc};
91 }
92 case dwarf::DW_LLE_default_location:
93 return DWARFLocationExpression{None, E.Loc};
94 case dwarf::DW_LLE_base_address:
95 Base = SectionedAddress{E.Value0, E.SectionIndex};
96 return None;
97 case dwarf::DW_LLE_start_end:
98 return DWARFLocationExpression{
99 DWARFAddressRange{E.Value0, E.Value1, E.SectionIndex}, E.Loc};
100 case dwarf::DW_LLE_start_length:
101 return DWARFLocationExpression{
102 DWARFAddressRange{E.Value0, E.Value0 + E.Value1, E.SectionIndex},
103 E.Loc};
104 default:
105 llvm_unreachable("unreachable locations list kind")::llvm::llvm_unreachable_internal("unreachable locations list kind"
, "/build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp"
, 105)
;
106 }
107}
108
109// When directly dumping the .debug_loc without a compile unit, we have to guess
110// at the DWARF version. This only affects DW_OP_call_ref, which is a rare
111// expression that LLVM doesn't produce. Guessing the wrong version means we
112// won't be able to pretty print expressions in DWARF2 binaries produced by
113// non-LLVM tools.
114static void dumpExpression(raw_ostream &OS, ArrayRef<uint8_t> Data,
115 bool IsLittleEndian, unsigned AddressSize,
116 const MCRegisterInfo *MRI, DWARFUnit *U) {
117 DWARFDataExtractor Extractor(toStringRef(Data), IsLittleEndian, AddressSize);
118 DWARFExpression(Extractor, dwarf::DWARF_VERSION, AddressSize).print(OS, MRI, U);
119}
120
121bool DWARFLocationTable::dumpLocationList(uint64_t *Offset, raw_ostream &OS,
122 Optional<SectionedAddress> BaseAddr,
123 const MCRegisterInfo *MRI,
124 const DWARFObject &Obj, DWARFUnit *U,
125 DIDumpOptions DumpOpts,
126 unsigned Indent) const {
127 DWARFLocationInterpreter Interp(
128 BaseAddr, [U](uint32_t Index) -> Optional<SectionedAddress> {
129 if (U)
130 return U->getAddrOffsetSectionItem(Index);
131 return None;
132 });
133 OS << format("0x%8.8" PRIx64"l" "x" ": ", *Offset);
134 Error E = visitLocationList(Offset, [&](const DWARFLocationEntry &E) {
135 Expected<Optional<DWARFLocationExpression>> Loc = Interp.Interpret(E);
136 if (!Loc || DumpOpts.DisplayRawContents)
137 dumpRawEntry(E, OS, Indent, DumpOpts, Obj);
138 if (Loc && *Loc) {
139 OS << "\n";
140 OS.indent(Indent);
141 if (DumpOpts.DisplayRawContents)
142 OS << " => ";
143
144 DIDumpOptions RangeDumpOpts(DumpOpts);
145 RangeDumpOpts.DisplayRawContents = false;
146 if (Loc.get()->Range)
147 Loc.get()->Range->dump(OS, Data.getAddressSize(), RangeDumpOpts, &Obj);
148 else
149 OS << "<default>";
150 }
151 if (!Loc)
152 consumeError(Loc.takeError());
153
154 if (E.Kind != dwarf::DW_LLE_base_address &&
155 E.Kind != dwarf::DW_LLE_base_addressx &&
156 E.Kind != dwarf::DW_LLE_end_of_list) {
157 OS << ": ";
158 dumpExpression(OS, E.Loc, Data.isLittleEndian(), Data.getAddressSize(),
159 MRI, U);
160 }
161 return true;
162 });
163 if (E) {
164 OS << "\n";
165 OS.indent(Indent);
166 OS << "error: " << toString(std::move(E));
167 return false;
168 }
169 return true;
170}
171
172Error DWARFLocationTable::visitAbsoluteLocationList(
173 uint64_t Offset, Optional<SectionedAddress> BaseAddr,
174 std::function<Optional<SectionedAddress>(uint32_t)> LookupAddr,
175 function_ref<bool(Expected<DWARFLocationExpression>)> Callback) const {
176 DWARFLocationInterpreter Interp(BaseAddr, std::move(LookupAddr));
177 return visitLocationList(&Offset, [&](const DWARFLocationEntry &E) {
178 Expected<Optional<DWARFLocationExpression>> Loc = Interp.Interpret(E);
179 if (!Loc)
180 return Callback(Loc.takeError());
181 if (*Loc)
182 return Callback(**Loc);
183 return true;
184 });
185}
186
187void DWARFDebugLoc::dump(raw_ostream &OS, const MCRegisterInfo *MRI,
188 const DWARFObject &Obj, DIDumpOptions DumpOpts,
189 Optional<uint64_t> DumpOffset) const {
190 auto BaseAddr = None;
191 unsigned Indent = 12;
192 if (DumpOffset) {
193 dumpLocationList(&*DumpOffset, OS, BaseAddr, MRI, Obj, nullptr, DumpOpts,
194 Indent);
195 } else {
196 uint64_t Offset = 0;
197 StringRef Separator;
198 bool CanContinue = true;
199 while (CanContinue && Data.isValidOffset(Offset)) {
200 OS << Separator;
201 Separator = "\n";
202
203 CanContinue = dumpLocationList(&Offset, OS, BaseAddr, MRI, Obj, nullptr,
204 DumpOpts, Indent);
205 OS << '\n';
206 }
207 }
208}
209
210Error DWARFDebugLoc::visitLocationList(
211 uint64_t *Offset,
212 function_ref<bool(const DWARFLocationEntry &)> Callback) const {
213 DataExtractor::Cursor C(*Offset);
214 while (true) {
215 uint64_t SectionIndex;
216 uint64_t Value0 = Data.getRelocatedAddress(C);
217 uint64_t Value1 = Data.getRelocatedAddress(C, &SectionIndex);
218
219 DWARFLocationEntry E;
220
221 // The end of any given location list is marked by an end of list entry,
222 // which consists of a 0 for the beginning address offset and a 0 for the
223 // ending address offset. A beginning offset of 0xff...f marks the base
224 // address selection entry.
225 if (Value0 == 0 && Value1 == 0) {
226 E.Kind = dwarf::DW_LLE_end_of_list;
227 } else if (Value0 == (Data.getAddressSize() == 4 ? -1U : -1ULL)) {
228 E.Kind = dwarf::DW_LLE_base_address;
229 E.Value0 = Value1;
230 E.SectionIndex = SectionIndex;
231 } else {
232 E.Kind = dwarf::DW_LLE_offset_pair;
233 E.Value0 = Value0;
234 E.Value1 = Value1;
235 E.SectionIndex = SectionIndex;
236 unsigned Bytes = Data.getU16(C);
237 // A single location description describing the location of the object...
238 Data.getU8(C, E.Loc, Bytes);
239 }
240
241 if (!C)
242 return C.takeError();
243 if (!Callback(E) || E.Kind == dwarf::DW_LLE_end_of_list)
244 break;
245 }
246 *Offset = C.tell();
247 return Error::success();
248}
249
250void DWARFDebugLoc::dumpRawEntry(const DWARFLocationEntry &Entry,
251 raw_ostream &OS, unsigned Indent,
252 DIDumpOptions DumpOpts,
253 const DWARFObject &Obj) const {
254 uint64_t Value0, Value1;
255 switch (Entry.Kind) {
256 case dwarf::DW_LLE_base_address:
257 Value0 = Data.getAddressSize() == 4 ? -1U : -1ULL;
258 Value1 = Entry.Value0;
259 break;
260 case dwarf::DW_LLE_offset_pair:
261 Value0 = Entry.Value0;
262 Value1 = Entry.Value1;
263 break;
264 case dwarf::DW_LLE_end_of_list:
265 Value0 = Value1 = 0;
Value stored to 'Value0' is never read
266 return;
267 default:
268 llvm_unreachable("Not possible in DWARF4!")::llvm::llvm_unreachable_internal("Not possible in DWARF4!", "/build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp"
, 268)
;
269 }
270 OS << '\n';
271 OS.indent(Indent);
272 OS << '(' << format_hex(Value0, 2 + Data.getAddressSize() * 2) << ", "
273 << format_hex(Value1, 2 + Data.getAddressSize() * 2) << ')';
274 DWARFFormValue::dumpAddressSection(Obj, OS, DumpOpts, Entry.SectionIndex);
275}
276
277Error DWARFDebugLoclists::visitLocationList(
278 uint64_t *Offset, function_ref<bool(const DWARFLocationEntry &)> F) const {
279
280 DataExtractor::Cursor C(*Offset);
281 bool Continue = true;
282 while (Continue) {
283 DWARFLocationEntry E;
284 E.Kind = Data.getU8(C);
285 switch (E.Kind) {
286 case dwarf::DW_LLE_end_of_list:
287 break;
288 case dwarf::DW_LLE_base_addressx:
289 E.Value0 = Data.getULEB128(C);
290 break;
291 case dwarf::DW_LLE_startx_endx:
292 E.Value0 = Data.getULEB128(C);
293 E.Value1 = Data.getULEB128(C);
294 break;
295 case dwarf::DW_LLE_startx_length:
296 E.Value0 = Data.getULEB128(C);
297 // Pre-DWARF 5 has different interpretation of the length field. We have
298 // to support both pre- and standartized styles for the compatibility.
299 if (Version < 5)
300 E.Value1 = Data.getU32(C);
301 else
302 E.Value1 = Data.getULEB128(C);
303 break;
304 case dwarf::DW_LLE_offset_pair:
305 E.Value0 = Data.getULEB128(C);
306 E.Value1 = Data.getULEB128(C);
307 E.SectionIndex = SectionedAddress::UndefSection;
308 break;
309 case dwarf::DW_LLE_default_location:
310 break;
311 case dwarf::DW_LLE_base_address:
312 E.Value0 = Data.getRelocatedAddress(C, &E.SectionIndex);
313 break;
314 case dwarf::DW_LLE_start_end:
315 E.Value0 = Data.getRelocatedAddress(C, &E.SectionIndex);
316 E.Value1 = Data.getRelocatedAddress(C);
317 break;
318 case dwarf::DW_LLE_start_length:
319 E.Value0 = Data.getRelocatedAddress(C, &E.SectionIndex);
320 E.Value1 = Data.getULEB128(C);
321 break;
322 default:
323 cantFail(C.takeError());
324 return createStringError(errc::illegal_byte_sequence,
325 "LLE of kind %x not supported", (int)E.Kind);
326 }
327
328 if (E.Kind != dwarf::DW_LLE_base_address &&
329 E.Kind != dwarf::DW_LLE_base_addressx &&
330 E.Kind != dwarf::DW_LLE_end_of_list) {
331 unsigned Bytes = Version >= 5 ? Data.getULEB128(C) : Data.getU16(C);
332 // A single location description describing the location of the object...
333 Data.getU8(C, E.Loc, Bytes);
334 }
335
336 if (!C)
337 return C.takeError();
338 Continue = F(E) && E.Kind != dwarf::DW_LLE_end_of_list;
339 }
340 *Offset = C.tell();
341 return Error::success();
342}
343
344void DWARFDebugLoclists::dumpRawEntry(const DWARFLocationEntry &Entry,
345 raw_ostream &OS, unsigned Indent,
346 DIDumpOptions DumpOpts,
347 const DWARFObject &Obj) const {
348 size_t MaxEncodingStringLength = 0;
349#define HANDLE_DW_LLE(ID, NAME) \
350 MaxEncodingStringLength = std::max(MaxEncodingStringLength, \
351 dwarf::LocListEncodingString(ID).size());
352#include "llvm/BinaryFormat/Dwarf.def"
353
354 OS << "\n";
355 OS.indent(Indent);
356 StringRef EncodingString = dwarf::LocListEncodingString(Entry.Kind);
357 // Unsupported encodings should have been reported during parsing.
358 assert(!EncodingString.empty() && "Unknown loclist entry encoding")((!EncodingString.empty() && "Unknown loclist entry encoding"
) ? static_cast<void> (0) : __assert_fail ("!EncodingString.empty() && \"Unknown loclist entry encoding\""
, "/build/llvm-toolchain-snapshot-10~++20200112100611+7fa5290d5bd/llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp"
, 358, __PRETTY_FUNCTION__))
;
359 OS << format("%-*s(", MaxEncodingStringLength, EncodingString.data());
360 unsigned FieldSize = 2 + 2 * Data.getAddressSize();
361 switch (Entry.Kind) {
362 case dwarf::DW_LLE_end_of_list:
363 case dwarf::DW_LLE_default_location:
364 break;
365 case dwarf::DW_LLE_startx_endx:
366 case dwarf::DW_LLE_startx_length:
367 case dwarf::DW_LLE_offset_pair:
368 case dwarf::DW_LLE_start_end:
369 case dwarf::DW_LLE_start_length:
370 OS << format_hex(Entry.Value0, FieldSize) << ", "
371 << format_hex(Entry.Value1, FieldSize);
372 break;
373 case dwarf::DW_LLE_base_addressx:
374 case dwarf::DW_LLE_base_address:
375 OS << format_hex(Entry.Value0, FieldSize);
376 break;
377 }
378 OS << ')';
379 switch (Entry.Kind) {
380 case dwarf::DW_LLE_base_address:
381 case dwarf::DW_LLE_start_end:
382 case dwarf::DW_LLE_start_length:
383 DWARFFormValue::dumpAddressSection(Obj, OS, DumpOpts, Entry.SectionIndex);
384 break;
385 default:
386 break;
387 }
388}
389
390void DWARFDebugLoclists::dumpRange(uint64_t StartOffset, uint64_t Size,
391 raw_ostream &OS, const MCRegisterInfo *MRI,
392 const DWARFObject &Obj,
393 DIDumpOptions DumpOpts) {
394 if (!Data.isValidOffsetForDataOfSize(StartOffset, Size)) {
395 OS << "Invalid dump range\n";
396 return;
397 }
398 uint64_t Offset = StartOffset;
399 StringRef Separator;
400 bool CanContinue = true;
401 while (CanContinue && Offset < StartOffset + Size) {
402 OS << Separator;
403 Separator = "\n";
404
405 CanContinue = dumpLocationList(&Offset, OS, /*BaseAddr=*/None, MRI, Obj,
406 nullptr, DumpOpts, /*Indent=*/12);
407 OS << '\n';
408 }
409}