Bug Summary

File:llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp
Warning:line 260, column 5
Value stored to 'Value0' is never read

Annotated Source Code

Press '?' to see keyboard shortcuts

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-11/lib/clang/11.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/build-llvm/lib/DebugInfo/DWARF -I /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/DebugInfo/DWARF -I /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/build-llvm/include -I /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/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-11/lib/clang/11.0.0/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-11~++20200309111110+2c36c23f347/build-llvm/lib/DebugInfo/DWARF -fdebug-prefix-map=/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347=. -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-2020-03-09-184146-41876-1 -x c++ /build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/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-11~++20200309111110+2c36c23f347/llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp"
, 105)
;
106 }
107}
108
109static void dumpExpression(raw_ostream &OS, ArrayRef<uint8_t> Data,
110 bool IsLittleEndian, unsigned AddressSize,
111 const MCRegisterInfo *MRI, DWARFUnit *U) {
112 DWARFDataExtractor Extractor(Data, IsLittleEndian, AddressSize);
113 DWARFExpression(Extractor, AddressSize).print(OS, MRI, U);
114}
115
116bool DWARFLocationTable::dumpLocationList(uint64_t *Offset, raw_ostream &OS,
117 Optional<SectionedAddress> BaseAddr,
118 const MCRegisterInfo *MRI,
119 const DWARFObject &Obj, DWARFUnit *U,
120 DIDumpOptions DumpOpts,
121 unsigned Indent) const {
122 DWARFLocationInterpreter Interp(
123 BaseAddr, [U](uint32_t Index) -> Optional<SectionedAddress> {
124 if (U)
125 return U->getAddrOffsetSectionItem(Index);
126 return None;
127 });
128 OS << format("0x%8.8" PRIx64"l" "x" ": ", *Offset);
129 Error E = visitLocationList(Offset, [&](const DWARFLocationEntry &E) {
130 Expected<Optional<DWARFLocationExpression>> Loc = Interp.Interpret(E);
131 if (!Loc || DumpOpts.DisplayRawContents)
132 dumpRawEntry(E, OS, Indent, DumpOpts, Obj);
133 if (Loc && *Loc) {
134 OS << "\n";
135 OS.indent(Indent);
136 if (DumpOpts.DisplayRawContents)
137 OS << " => ";
138
139 DIDumpOptions RangeDumpOpts(DumpOpts);
140 RangeDumpOpts.DisplayRawContents = false;
141 if (Loc.get()->Range)
142 Loc.get()->Range->dump(OS, Data.getAddressSize(), RangeDumpOpts, &Obj);
143 else
144 OS << "<default>";
145 }
146 if (!Loc)
147 consumeError(Loc.takeError());
148
149 if (E.Kind != dwarf::DW_LLE_base_address &&
150 E.Kind != dwarf::DW_LLE_base_addressx &&
151 E.Kind != dwarf::DW_LLE_end_of_list) {
152 OS << ": ";
153 dumpExpression(OS, E.Loc, Data.isLittleEndian(), Data.getAddressSize(),
154 MRI, U);
155 }
156 return true;
157 });
158 if (E) {
159 OS << "\n";
160 OS.indent(Indent);
161 OS << "error: " << toString(std::move(E));
162 return false;
163 }
164 return true;
165}
166
167Error DWARFLocationTable::visitAbsoluteLocationList(
168 uint64_t Offset, Optional<SectionedAddress> BaseAddr,
169 std::function<Optional<SectionedAddress>(uint32_t)> LookupAddr,
170 function_ref<bool(Expected<DWARFLocationExpression>)> Callback) const {
171 DWARFLocationInterpreter Interp(BaseAddr, std::move(LookupAddr));
172 return visitLocationList(&Offset, [&](const DWARFLocationEntry &E) {
173 Expected<Optional<DWARFLocationExpression>> Loc = Interp.Interpret(E);
174 if (!Loc)
175 return Callback(Loc.takeError());
176 if (*Loc)
177 return Callback(**Loc);
178 return true;
179 });
180}
181
182void DWARFDebugLoc::dump(raw_ostream &OS, const MCRegisterInfo *MRI,
183 const DWARFObject &Obj, DIDumpOptions DumpOpts,
184 Optional<uint64_t> DumpOffset) const {
185 auto BaseAddr = None;
186 unsigned Indent = 12;
187 if (DumpOffset) {
188 dumpLocationList(&*DumpOffset, OS, BaseAddr, MRI, Obj, nullptr, DumpOpts,
189 Indent);
190 } else {
191 uint64_t Offset = 0;
192 StringRef Separator;
193 bool CanContinue = true;
194 while (CanContinue && Data.isValidOffset(Offset)) {
195 OS << Separator;
196 Separator = "\n";
197
198 CanContinue = dumpLocationList(&Offset, OS, BaseAddr, MRI, Obj, nullptr,
199 DumpOpts, Indent);
200 OS << '\n';
201 }
202 }
203}
204
205Error DWARFDebugLoc::visitLocationList(
206 uint64_t *Offset,
207 function_ref<bool(const DWARFLocationEntry &)> Callback) const {
208 DataExtractor::Cursor C(*Offset);
209 while (true) {
210 uint64_t SectionIndex;
211 uint64_t Value0 = Data.getRelocatedAddress(C);
212 uint64_t Value1 = Data.getRelocatedAddress(C, &SectionIndex);
213
214 DWARFLocationEntry E;
215
216 // The end of any given location list is marked by an end of list entry,
217 // which consists of a 0 for the beginning address offset and a 0 for the
218 // ending address offset. A beginning offset of 0xff...f marks the base
219 // address selection entry.
220 if (Value0 == 0 && Value1 == 0) {
221 E.Kind = dwarf::DW_LLE_end_of_list;
222 } else if (Value0 == (Data.getAddressSize() == 4 ? -1U : -1ULL)) {
223 E.Kind = dwarf::DW_LLE_base_address;
224 E.Value0 = Value1;
225 E.SectionIndex = SectionIndex;
226 } else {
227 E.Kind = dwarf::DW_LLE_offset_pair;
228 E.Value0 = Value0;
229 E.Value1 = Value1;
230 E.SectionIndex = SectionIndex;
231 unsigned Bytes = Data.getU16(C);
232 // A single location description describing the location of the object...
233 Data.getU8(C, E.Loc, Bytes);
234 }
235
236 if (!C)
237 return C.takeError();
238 if (!Callback(E) || E.Kind == dwarf::DW_LLE_end_of_list)
239 break;
240 }
241 *Offset = C.tell();
242 return Error::success();
243}
244
245void DWARFDebugLoc::dumpRawEntry(const DWARFLocationEntry &Entry,
246 raw_ostream &OS, unsigned Indent,
247 DIDumpOptions DumpOpts,
248 const DWARFObject &Obj) const {
249 uint64_t Value0, Value1;
250 switch (Entry.Kind) {
251 case dwarf::DW_LLE_base_address:
252 Value0 = Data.getAddressSize() == 4 ? -1U : -1ULL;
253 Value1 = Entry.Value0;
254 break;
255 case dwarf::DW_LLE_offset_pair:
256 Value0 = Entry.Value0;
257 Value1 = Entry.Value1;
258 break;
259 case dwarf::DW_LLE_end_of_list:
260 Value0 = Value1 = 0;
Value stored to 'Value0' is never read
261 return;
262 default:
263 llvm_unreachable("Not possible in DWARF4!")::llvm::llvm_unreachable_internal("Not possible in DWARF4!", "/build/llvm-toolchain-snapshot-11~++20200309111110+2c36c23f347/llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp"
, 263)
;
264 }
265 OS << '\n';
266 OS.indent(Indent);
267 OS << '(' << format_hex(Value0, 2 + Data.getAddressSize() * 2) << ", "
268 << format_hex(Value1, 2 + Data.getAddressSize() * 2) << ')';
269 DWARFFormValue::dumpAddressSection(Obj, OS, DumpOpts, Entry.SectionIndex);
270}
271
272Error DWARFDebugLoclists::visitLocationList(
273 uint64_t *Offset, function_ref<bool(const DWARFLocationEntry &)> F) const {
274
275 DataExtractor::Cursor C(*Offset);
276 bool Continue = true;
277 while (Continue) {
278 DWARFLocationEntry E;
279 E.Kind = Data.getU8(C);
280 switch (E.Kind) {
281 case dwarf::DW_LLE_end_of_list:
282 break;
283 case dwarf::DW_LLE_base_addressx:
284 E.Value0 = Data.getULEB128(C);
285 break;
286 case dwarf::DW_LLE_startx_endx:
287 E.Value0 = Data.getULEB128(C);
288 E.Value1 = Data.getULEB128(C);
289 break;
290 case dwarf::DW_LLE_startx_length:
291 E.Value0 = Data.getULEB128(C);
292 // Pre-DWARF 5 has different interpretation of the length field. We have
293 // to support both pre- and standartized styles for the compatibility.
294 if (Version < 5)
295 E.Value1 = Data.getU32(C);
296 else
297 E.Value1 = Data.getULEB128(C);
298 break;
299 case dwarf::DW_LLE_offset_pair:
300 E.Value0 = Data.getULEB128(C);
301 E.Value1 = Data.getULEB128(C);
302 E.SectionIndex = SectionedAddress::UndefSection;
303 break;
304 case dwarf::DW_LLE_default_location:
305 break;
306 case dwarf::DW_LLE_base_address:
307 E.Value0 = Data.getRelocatedAddress(C, &E.SectionIndex);
308 break;
309 case dwarf::DW_LLE_start_end:
310 E.Value0 = Data.getRelocatedAddress(C, &E.SectionIndex);
311 E.Value1 = Data.getRelocatedAddress(C);
312 break;
313 case dwarf::DW_LLE_start_length:
314 E.Value0 = Data.getRelocatedAddress(C, &E.SectionIndex);
315 E.Value1 = Data.getULEB128(C);
316 break;
317 default:
318 cantFail(C.takeError());
319 return createStringError(errc::illegal_byte_sequence,
320 "LLE of kind %x not supported", (int)E.Kind);
321 }
322
323 if (E.Kind != dwarf::DW_LLE_base_address &&
324 E.Kind != dwarf::DW_LLE_base_addressx &&
325 E.Kind != dwarf::DW_LLE_end_of_list) {
326 unsigned Bytes = Version >= 5 ? Data.getULEB128(C) : Data.getU16(C);
327 // A single location description describing the location of the object...
328 Data.getU8(C, E.Loc, Bytes);
329 }
330
331 if (!C)
332 return C.takeError();
333 Continue = F(E) && E.Kind != dwarf::DW_LLE_end_of_list;
334 }
335 *Offset = C.tell();
336 return Error::success();
337}
338
339void DWARFDebugLoclists::dumpRawEntry(const DWARFLocationEntry &Entry,
340 raw_ostream &OS, unsigned Indent,
341 DIDumpOptions DumpOpts,
342 const DWARFObject &Obj) const {
343 size_t MaxEncodingStringLength = 0;
344#define HANDLE_DW_LLE(ID, NAME) \
345 MaxEncodingStringLength = std::max(MaxEncodingStringLength, \
346 dwarf::LocListEncodingString(ID).size());
347#include "llvm/BinaryFormat/Dwarf.def"
348
349 OS << "\n";
350 OS.indent(Indent);
351 StringRef EncodingString = dwarf::LocListEncodingString(Entry.Kind);
352 // Unsupported encodings should have been reported during parsing.
353 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-11~++20200309111110+2c36c23f347/llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp"
, 353, __PRETTY_FUNCTION__))
;
354 OS << format("%-*s(", MaxEncodingStringLength, EncodingString.data());
355 unsigned FieldSize = 2 + 2 * Data.getAddressSize();
356 switch (Entry.Kind) {
357 case dwarf::DW_LLE_end_of_list:
358 case dwarf::DW_LLE_default_location:
359 break;
360 case dwarf::DW_LLE_startx_endx:
361 case dwarf::DW_LLE_startx_length:
362 case dwarf::DW_LLE_offset_pair:
363 case dwarf::DW_LLE_start_end:
364 case dwarf::DW_LLE_start_length:
365 OS << format_hex(Entry.Value0, FieldSize) << ", "
366 << format_hex(Entry.Value1, FieldSize);
367 break;
368 case dwarf::DW_LLE_base_addressx:
369 case dwarf::DW_LLE_base_address:
370 OS << format_hex(Entry.Value0, FieldSize);
371 break;
372 }
373 OS << ')';
374 switch (Entry.Kind) {
375 case dwarf::DW_LLE_base_address:
376 case dwarf::DW_LLE_start_end:
377 case dwarf::DW_LLE_start_length:
378 DWARFFormValue::dumpAddressSection(Obj, OS, DumpOpts, Entry.SectionIndex);
379 break;
380 default:
381 break;
382 }
383}
384
385void DWARFDebugLoclists::dumpRange(uint64_t StartOffset, uint64_t Size,
386 raw_ostream &OS, const MCRegisterInfo *MRI,
387 const DWARFObject &Obj,
388 DIDumpOptions DumpOpts) {
389 if (!Data.isValidOffsetForDataOfSize(StartOffset, Size)) {
390 OS << "Invalid dump range\n";
391 return;
392 }
393 uint64_t Offset = StartOffset;
394 StringRef Separator;
395 bool CanContinue = true;
396 while (CanContinue && Offset < StartOffset + Size) {
397 OS << Separator;
398 Separator = "\n";
399
400 CanContinue = dumpLocationList(&Offset, OS, /*BaseAddr=*/None, MRI, Obj,
401 nullptr, DumpOpts, /*Indent=*/12);
402 OS << '\n';
403 }
404}