Bug Summary

File:llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp
Warning:line 263, column 5
Value stored to 'Value0' is never read

Annotated Source Code

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clang -cc1 -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 -fhalf-no-semantic-interposition -mframe-pointer=none -fmath-errno -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -tune-cpu generic -fno-split-dwarf-inlining -debugger-tuning=gdb -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-12/lib/clang/12.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-12~++20210107111113+c9154e8fa377/build-llvm/lib/DebugInfo/DWARF -I /build/llvm-toolchain-snapshot-12~++20210107111113+c9154e8fa377/llvm/lib/DebugInfo/DWARF -I /build/llvm-toolchain-snapshot-12~++20210107111113+c9154e8fa377/build-llvm/include -I /build/llvm-toolchain-snapshot-12~++20210107111113+c9154e8fa377/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-12/lib/clang/12.0.0/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-12~++20210107111113+c9154e8fa377/build-llvm/lib/DebugInfo/DWARF -fdebug-prefix-map=/build/llvm-toolchain-snapshot-12~++20210107111113+c9154e8fa377=. -ferror-limit 19 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -o /tmp/scan-build-2021-01-08-143434-21064-1 -x c++ /build/llvm-toolchain-snapshot-12~++20210107111113+c9154e8fa377/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-12~++20210107111113+c9154e8fa377/llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp"
, 105);
106 }
107}
108
109static void dumpExpression(raw_ostream &OS, DIDumpOptions DumpOpts,
110 ArrayRef<uint8_t> Data, bool IsLittleEndian,
111 unsigned AddressSize, const MCRegisterInfo *MRI,
112 DWARFUnit *U) {
113 DWARFDataExtractor Extractor(Data, IsLittleEndian, AddressSize);
114 // Note. We do not pass any format to DWARFExpression, even if the
115 // corresponding unit is known. For now, there is only one operation,
116 // DW_OP_call_ref, which depends on the format; it is rarely used, and
117 // is unexpected in location tables.
118 DWARFExpression(Extractor, AddressSize).print(OS, DumpOpts, 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, DumpOpts, E.Loc, Data.isLittleEndian(),
159 Data.getAddressSize(), MRI, U);
160 }
161 return true;
162 });
163 if (E) {
164 DumpOpts.RecoverableErrorHandler(std::move(E));
165 return false;
166 }
167 return true;
168}
169
170Error DWARFLocationTable::visitAbsoluteLocationList(
171 uint64_t Offset, Optional<SectionedAddress> BaseAddr,
172 std::function<Optional<SectionedAddress>(uint32_t)> LookupAddr,
173 function_ref<bool(Expected<DWARFLocationExpression>)> Callback) const {
174 DWARFLocationInterpreter Interp(BaseAddr, std::move(LookupAddr));
175 return visitLocationList(&Offset, [&](const DWARFLocationEntry &E) {
176 Expected<Optional<DWARFLocationExpression>> Loc = Interp.Interpret(E);
177 if (!Loc)
178 return Callback(Loc.takeError());
179 if (*Loc)
180 return Callback(**Loc);
181 return true;
182 });
183}
184
185void DWARFDebugLoc::dump(raw_ostream &OS, const MCRegisterInfo *MRI,
186 const DWARFObject &Obj, DIDumpOptions DumpOpts,
187 Optional<uint64_t> DumpOffset) const {
188 auto BaseAddr = None;
189 unsigned Indent = 12;
190 if (DumpOffset) {
191 dumpLocationList(&*DumpOffset, OS, BaseAddr, MRI, Obj, nullptr, DumpOpts,
192 Indent);
193 } else {
194 uint64_t Offset = 0;
195 StringRef Separator;
196 bool CanContinue = true;
197 while (CanContinue && Data.isValidOffset(Offset)) {
198 OS << Separator;
199 Separator = "\n";
200
201 CanContinue = dumpLocationList(&Offset, OS, BaseAddr, MRI, Obj, nullptr,
202 DumpOpts, Indent);
203 OS << '\n';
204 }
205 }
206}
207
208Error DWARFDebugLoc::visitLocationList(
209 uint64_t *Offset,
210 function_ref<bool(const DWARFLocationEntry &)> Callback) const {
211 DataExtractor::Cursor C(*Offset);
212 while (true) {
213 uint64_t SectionIndex;
214 uint64_t Value0 = Data.getRelocatedAddress(C);
215 uint64_t Value1 = Data.getRelocatedAddress(C, &SectionIndex);
216
217 DWARFLocationEntry E;
218
219 // The end of any given location list is marked by an end of list entry,
220 // which consists of a 0 for the beginning address offset and a 0 for the
221 // ending address offset. A beginning offset of 0xff...f marks the base
222 // address selection entry.
223 if (Value0 == 0 && Value1 == 0) {
224 E.Kind = dwarf::DW_LLE_end_of_list;
225 } else if (Value0 == (Data.getAddressSize() == 4 ? -1U : -1ULL)) {
226 E.Kind = dwarf::DW_LLE_base_address;
227 E.Value0 = Value1;
228 E.SectionIndex = SectionIndex;
229 } else {
230 E.Kind = dwarf::DW_LLE_offset_pair;
231 E.Value0 = Value0;
232 E.Value1 = Value1;
233 E.SectionIndex = SectionIndex;
234 unsigned Bytes = Data.getU16(C);
235 // A single location description describing the location of the object...
236 Data.getU8(C, E.Loc, Bytes);
237 }
238
239 if (!C)
240 return C.takeError();
241 if (!Callback(E) || E.Kind == dwarf::DW_LLE_end_of_list)
242 break;
243 }
244 *Offset = C.tell();
245 return Error::success();
246}
247
248void DWARFDebugLoc::dumpRawEntry(const DWARFLocationEntry &Entry,
249 raw_ostream &OS, unsigned Indent,
250 DIDumpOptions DumpOpts,
251 const DWARFObject &Obj) const {
252 uint64_t Value0, Value1;
253 switch (Entry.Kind) {
254 case dwarf::DW_LLE_base_address:
255 Value0 = Data.getAddressSize() == 4 ? -1U : -1ULL;
256 Value1 = Entry.Value0;
257 break;
258 case dwarf::DW_LLE_offset_pair:
259 Value0 = Entry.Value0;
260 Value1 = Entry.Value1;
261 break;
262 case dwarf::DW_LLE_end_of_list:
263 Value0 = Value1 = 0;
Value stored to 'Value0' is never read
264 return;
265 default:
266 llvm_unreachable("Not possible in DWARF4!")::llvm::llvm_unreachable_internal("Not possible in DWARF4!", "/build/llvm-toolchain-snapshot-12~++20210107111113+c9154e8fa377/llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp"
, 266);
267 }
268 OS << '\n';
269 OS.indent(Indent);
270 OS << '(' << format_hex(Value0, 2 + Data.getAddressSize() * 2) << ", "
271 << format_hex(Value1, 2 + Data.getAddressSize() * 2) << ')';
272 DWARFFormValue::dumpAddressSection(Obj, OS, DumpOpts, Entry.SectionIndex);
273}
274
275Error DWARFDebugLoclists::visitLocationList(
276 uint64_t *Offset, function_ref<bool(const DWARFLocationEntry &)> F) const {
277
278 DataExtractor::Cursor C(*Offset);
279 bool Continue = true;
280 while (Continue) {
281 DWARFLocationEntry E;
282 E.Kind = Data.getU8(C);
283 switch (E.Kind) {
284 case dwarf::DW_LLE_end_of_list:
285 break;
286 case dwarf::DW_LLE_base_addressx:
287 E.Value0 = Data.getULEB128(C);
288 break;
289 case dwarf::DW_LLE_startx_endx:
290 E.Value0 = Data.getULEB128(C);
291 E.Value1 = Data.getULEB128(C);
292 break;
293 case dwarf::DW_LLE_startx_length:
294 E.Value0 = Data.getULEB128(C);
295 // Pre-DWARF 5 has different interpretation of the length field. We have
296 // to support both pre- and standartized styles for the compatibility.
297 if (Version < 5)
298 E.Value1 = Data.getU32(C);
299 else
300 E.Value1 = Data.getULEB128(C);
301 break;
302 case dwarf::DW_LLE_offset_pair:
303 E.Value0 = Data.getULEB128(C);
304 E.Value1 = Data.getULEB128(C);
305 E.SectionIndex = SectionedAddress::UndefSection;
306 break;
307 case dwarf::DW_LLE_default_location:
308 break;
309 case dwarf::DW_LLE_base_address:
310 E.Value0 = Data.getRelocatedAddress(C, &E.SectionIndex);
311 break;
312 case dwarf::DW_LLE_start_end:
313 E.Value0 = Data.getRelocatedAddress(C, &E.SectionIndex);
314 E.Value1 = Data.getRelocatedAddress(C);
315 break;
316 case dwarf::DW_LLE_start_length:
317 E.Value0 = Data.getRelocatedAddress(C, &E.SectionIndex);
318 E.Value1 = Data.getULEB128(C);
319 break;
320 default:
321 cantFail(C.takeError());
322 return createStringError(errc::illegal_byte_sequence,
323 "LLE of kind %x not supported", (int)E.Kind);
324 }
325
326 if (E.Kind != dwarf::DW_LLE_base_address &&
327 E.Kind != dwarf::DW_LLE_base_addressx &&
328 E.Kind != dwarf::DW_LLE_end_of_list) {
329 unsigned Bytes = Version >= 5 ? Data.getULEB128(C) : Data.getU16(C);
330 // A single location description describing the location of the object...
331 Data.getU8(C, E.Loc, Bytes);
332 }
333
334 if (!C)
335 return C.takeError();
336 Continue = F(E) && E.Kind != dwarf::DW_LLE_end_of_list;
337 }
338 *Offset = C.tell();
339 return Error::success();
340}
341
342void DWARFDebugLoclists::dumpRawEntry(const DWARFLocationEntry &Entry,
343 raw_ostream &OS, unsigned Indent,
344 DIDumpOptions DumpOpts,
345 const DWARFObject &Obj) const {
346 size_t MaxEncodingStringLength = 0;
347#define HANDLE_DW_LLE(ID, NAME) \
348 MaxEncodingStringLength = std::max(MaxEncodingStringLength, \
349 dwarf::LocListEncodingString(ID).size());
350#include "llvm/BinaryFormat/Dwarf.def"
351
352 OS << "\n";
353 OS.indent(Indent);
354 StringRef EncodingString = dwarf::LocListEncodingString(Entry.Kind);
355 // Unsupported encodings should have been reported during parsing.
356 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-12~++20210107111113+c9154e8fa377/llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp"
, 356, __PRETTY_FUNCTION__));
357 OS << format("%-*s(", MaxEncodingStringLength, EncodingString.data());
358 unsigned FieldSize = 2 + 2 * Data.getAddressSize();
359 switch (Entry.Kind) {
360 case dwarf::DW_LLE_end_of_list:
361 case dwarf::DW_LLE_default_location:
362 break;
363 case dwarf::DW_LLE_startx_endx:
364 case dwarf::DW_LLE_startx_length:
365 case dwarf::DW_LLE_offset_pair:
366 case dwarf::DW_LLE_start_end:
367 case dwarf::DW_LLE_start_length:
368 OS << format_hex(Entry.Value0, FieldSize) << ", "
369 << format_hex(Entry.Value1, FieldSize);
370 break;
371 case dwarf::DW_LLE_base_addressx:
372 case dwarf::DW_LLE_base_address:
373 OS << format_hex(Entry.Value0, FieldSize);
374 break;
375 }
376 OS << ')';
377 switch (Entry.Kind) {
378 case dwarf::DW_LLE_base_address:
379 case dwarf::DW_LLE_start_end:
380 case dwarf::DW_LLE_start_length:
381 DWARFFormValue::dumpAddressSection(Obj, OS, DumpOpts, Entry.SectionIndex);
382 break;
383 default:
384 break;
385 }
386}
387
388void DWARFDebugLoclists::dumpRange(uint64_t StartOffset, uint64_t Size,
389 raw_ostream &OS, const MCRegisterInfo *MRI,
390 const DWARFObject &Obj,
391 DIDumpOptions DumpOpts) {
392 if (!Data.isValidOffsetForDataOfSize(StartOffset, Size)) {
393 OS << "Invalid dump range\n";
394 return;
395 }
396 uint64_t Offset = StartOffset;
397 StringRef Separator;
398 bool CanContinue = true;
399 while (CanContinue && Offset < StartOffset + Size) {
400 OS << Separator;
401 Separator = "\n";
402
403 CanContinue = dumpLocationList(&Offset, OS, /*BaseAddr=*/None, MRI, Obj,
404 nullptr, DumpOpts, /*Indent=*/12);
405 OS << '\n';
406 }
407}