Bug Summary

File:tools/lld/COFF/InputFiles.cpp
Warning:line 176, column 11
Called C++ object pointer is null

Annotated Source Code

1//===- InputFiles.cpp -----------------------------------------------------===//
2//
3// The LLVM Linker
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#include "InputFiles.h"
11#include "Chunks.h"
12#include "Config.h"
13#include "Driver.h"
14#include "Error.h"
15#include "Memory.h"
16#include "SymbolTable.h"
17#include "Symbols.h"
18#include "llvm-c/lto.h"
19#include "llvm/ADT/SmallVector.h"
20#include "llvm/ADT/Triple.h"
21#include "llvm/ADT/Twine.h"
22#include "llvm/BinaryFormat/COFF.h"
23#include "llvm/Object/Binary.h"
24#include "llvm/Object/COFF.h"
25#include "llvm/Support/Casting.h"
26#include "llvm/Support/Endian.h"
27#include "llvm/Support/Error.h"
28#include "llvm/Support/ErrorOr.h"
29#include "llvm/Support/FileSystem.h"
30#include "llvm/Target/TargetOptions.h"
31#include <cstring>
32#include <system_error>
33#include <utility>
34
35using namespace llvm;
36using namespace llvm::COFF;
37using namespace llvm::object;
38using namespace llvm::support::endian;
39
40using llvm::Triple;
41using llvm::support::ulittle32_t;
42
43namespace lld {
44namespace coff {
45
46/// Checks that Source is compatible with being a weak alias to Target.
47/// If Source is Undefined and has no weak alias set, makes it a weak
48/// alias to Target.
49static void checkAndSetWeakAlias(SymbolTable *Symtab, InputFile *F,
50 SymbolBody *Source, SymbolBody *Target) {
51 if (auto *U = dyn_cast<Undefined>(Source)) {
52 if (U->WeakAlias && U->WeakAlias != Target)
53 Symtab->reportDuplicate(Source->symbol(), F);
54 U->WeakAlias = Target;
55 }
56}
57
58ArchiveFile::ArchiveFile(MemoryBufferRef M) : InputFile(ArchiveKind, M) {}
59
60void ArchiveFile::parse() {
61 // Parse a MemoryBufferRef as an archive file.
62 File = check(Archive::create(MB), toString(this));
63
64 // Read the symbol table to construct Lazy objects.
65 for (const Archive::Symbol &Sym : File->symbols())
66 Symtab->addLazy(this, Sym);
67}
68
69// Returns a buffer pointing to a member file containing a given symbol.
70void ArchiveFile::addMember(const Archive::Symbol *Sym) {
71 const Archive::Child &C =
72 check(Sym->getMember(),
73 "could not get the member for symbol " + Sym->getName());
74
75 // Return an empty buffer if we have already returned the same buffer.
76 if (!Seen.insert(C.getChildOffset()).second)
77 return;
78
79 Driver->enqueueArchiveMember(C, Sym->getName(), getName());
80}
81
82void ObjectFile::parse() {
83 // Parse a memory buffer as a COFF file.
84 std::unique_ptr<Binary> Bin = check(createBinary(MB), toString(this));
85
86 if (auto *Obj = dyn_cast<COFFObjectFile>(Bin.get())) {
1
Assuming 'Obj' is non-null
→
2
←
Taking true branch
→
87 Bin.release();
88 COFFObj.reset(Obj);
89 } else {
90 fatal(toString(this) + " is not a COFF file");
91 }
92
93 // Read section and symbol tables.
94 initializeChunks();
95 initializeSymbols();
3
←
Calling 'ObjectFile::initializeSymbols'
→
96 initializeSEH();
97}
98
99void ObjectFile::initializeChunks() {
100 uint32_t NumSections = COFFObj->getNumberOfSections();
101 Chunks.reserve(NumSections);
102 SparseChunks.resize(NumSections + 1);
103 for (uint32_t I = 1; I < NumSections + 1; ++I) {
104 const coff_section *Sec;
105 StringRef Name;
106 if (auto EC = COFFObj->getSection(I, Sec))
107 fatal(EC, "getSection failed: #" + Twine(I));
108 if (auto EC = COFFObj->getSectionName(Sec, Name))
109 fatal(EC, "getSectionName failed: #" + Twine(I));
110 if (Name == ".sxdata") {
111 SXData = Sec;
112 continue;
113 }
114 if (Name == ".drectve") {
115 ArrayRef<uint8_t> Data;
116 COFFObj->getSectionContents(Sec, Data);
117 Directives = std::string((const char *)Data.data(), Data.size());
118 continue;
119 }
120
121 // Object files may have DWARF debug info or MS CodeView debug info
122 // (or both).
123 //
124 // DWARF sections don't need any special handling from the perspective
125 // of the linker; they are just a data section containing relocations.
126 // We can just link them to complete debug info.
127 //
128 // CodeView needs a linker support. We need to interpret and debug
129 // info, and then write it to a separate .pdb file.
130
131 // Ignore debug info unless /debug is given.
132 if (!Config->Debug && Name.startswith(".debug"))
133 continue;
134
135 if (Sec->Characteristics & llvm::COFF::IMAGE_SCN_LNK_REMOVE)
136 continue;
137 auto *C = make<SectionChunk>(this, Sec);
138
139 // CodeView sections are stored to a different vector because they are not
140 // linked in the regular manner.
141 if (C->isCodeView())
142 DebugChunks.push_back(C);
143 else
144 Chunks.push_back(C);
145
146 SparseChunks[I] = C;
147 }
148}
149
150void ObjectFile::initializeSymbols() {
151 uint32_t NumSymbols = COFFObj->getNumberOfSymbols();
152 SymbolBodies.reserve(NumSymbols);
153 SparseSymbolBodies.resize(NumSymbols);
154
155 SmallVector<std::pair<SymbolBody *, uint32_t>, 8> WeakAliases;
156 int32_t LastSectionNumber = 0;
157
158 for (uint32_t I = 0; I < NumSymbols; ++I) {
4
←
Assuming 'I' is < 'NumSymbols'
→
5
←
Loop condition is true. Entering loop body
→
13
←
Loop condition is true. Entering loop body
→
20
←
Loop condition is true. Entering loop body
→
27
←
Loop condition is true. Entering loop body
→
159 // Get a COFFSymbolRef object.
160 ErrorOr<COFFSymbolRef> SymOrErr = COFFObj->getSymbol(I);
161 if (!SymOrErr)
6
←
Taking false branch
→
14
←
Taking false branch
→
21
←
Taking false branch
→
28
←
Taking false branch
→
162 fatal(SymOrErr.getError(), "broken object file: " + toString(this));
163 COFFSymbolRef Sym = *SymOrErr;
164
165 const void *AuxP = nullptr;
29
←
'AuxP' initialized to a null pointer value
→
166 if (Sym.getNumberOfAuxSymbols())
7
←
Taking false branch
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15
←
Taking false branch
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22
←
Taking false branch
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30
←
Taking false branch
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167 AuxP = COFFObj->getSymbol(I + 1)->getRawPtr();
168 bool IsFirst = (LastSectionNumber != Sym.getSectionNumber());
8
←
Assuming the condition is false
→
169
170 SymbolBody *Body = nullptr;
171 if (Sym.isUndefined()) {
9
←
Taking false branch
→
16
←
Taking false branch
→
23
←
Taking false branch
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31
←
Taking false branch
→
172 Body = createUndefined(Sym);
173 } else if (Sym.isWeakExternal()) {
10
←
Taking false branch
→
17
←
Taking false branch
→
24
←
Taking false branch
→
32
←
Taking true branch
→
174 Body = createUndefined(Sym);
175 uint32_t TagIndex =
176 static_cast<const coff_aux_weak_external *>(AuxP)->TagIndex;
33
←
Called C++ object pointer is null
177 WeakAliases.emplace_back(Body, TagIndex);
178 } else {
179 Body = createDefined(Sym, AuxP, IsFirst);
180 }
181 if (Body) {
11
←
Assuming 'Body' is null
→
12
←
Taking false branch
→
18
←
Assuming 'Body' is null
→
19
←
Taking false branch
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25
←
Assuming 'Body' is null
→
26
←
Taking false branch
→
182 SymbolBodies.push_back(Body);
183 SparseSymbolBodies[I] = Body;
184 }
185 I += Sym.getNumberOfAuxSymbols();
186 LastSectionNumber = Sym.getSectionNumber();
187 }
188
189 for (auto &KV : WeakAliases) {
190 SymbolBody *Sym = KV.first;
191 uint32_t Idx = KV.second;
192 checkAndSetWeakAlias(Symtab, this, Sym, SparseSymbolBodies[Idx]);
193 }
194}
195
196SymbolBody *ObjectFile::createUndefined(COFFSymbolRef Sym) {
197 StringRef Name;
198 COFFObj->getSymbolName(Sym, Name);
199 return Symtab->addUndefined(Name, this, Sym.isWeakExternal())->body();
200}
201
202SymbolBody *ObjectFile::createDefined(COFFSymbolRef Sym, const void *AuxP,
203 bool IsFirst) {
204 StringRef Name;
205 if (Sym.isCommon()) {
206 auto *C = make<CommonChunk>(Sym);
207 Chunks.push_back(C);
208 COFFObj->getSymbolName(Sym, Name);
209 Symbol *S =
210 Symtab->addCommon(this, Name, Sym.getValue(), Sym.getGeneric(), C);
211 return S->body();
212 }
213 if (Sym.isAbsolute()) {
214 COFFObj->getSymbolName(Sym, Name);
215 // Skip special symbols.
216 if (Name == "@comp.id")
217 return nullptr;
218 // COFF spec 5.10.1. The .sxdata section.
219 if (Name == "@feat.00") {
220 if (Sym.getValue() & 1)
221 SEHCompat = true;
222 return nullptr;
223 }
224 if (Sym.isExternal())
225 return Symtab->addAbsolute(Name, Sym)->body();
226 else
227 return make<DefinedAbsolute>(Name, Sym);
228 }
229 int32_t SectionNumber = Sym.getSectionNumber();
230 if (SectionNumber == llvm::COFF::IMAGE_SYM_DEBUG)
231 return nullptr;
232
233 // Reserved sections numbers don't have contents.
234 if (llvm::COFF::isReservedSectionNumber(SectionNumber))
235 fatal("broken object file: " + toString(this));
236
237 // This symbol references a section which is not present in the section
238 // header.
239 if ((uint32_t)SectionNumber >= SparseChunks.size())
240 fatal("broken object file: " + toString(this));
241
242 // Nothing else to do without a section chunk.
243 auto *SC = cast_or_null<SectionChunk>(SparseChunks[SectionNumber]);
244 if (!SC)
245 return nullptr;
246
247 // Handle section definitions
248 if (IsFirst && AuxP) {
249 auto *Aux = reinterpret_cast<const coff_aux_section_definition *>(AuxP);
250 if (Aux->Selection == IMAGE_COMDAT_SELECT_ASSOCIATIVE)
251 if (auto *ParentSC = cast_or_null<SectionChunk>(
252 SparseChunks[Aux->getNumber(Sym.isBigObj())])) {
253 ParentSC->addAssociative(SC);
254 // If we already discarded the parent, discard the child.
255 if (ParentSC->isDiscarded())
256 SC->markDiscarded();
257 }
258 SC->Checksum = Aux->CheckSum;
259 }
260
261 DefinedRegular *B;
262 if (Sym.isExternal()) {
263 COFFObj->getSymbolName(Sym, Name);
264 Symbol *S =
265 Symtab->addRegular(this, Name, SC->isCOMDAT(), Sym.getGeneric(), SC);
266 B = cast<DefinedRegular>(S->body());
267 } else
268 B = make<DefinedRegular>(this, /*Name*/ "", SC->isCOMDAT(),
269 /*IsExternal*/ false, Sym.getGeneric(), SC);
270 if (SC->isCOMDAT() && Sym.getValue() == 0 && !AuxP)
271 SC->setSymbol(B);
272
273 return B;
274}
275
276void ObjectFile::initializeSEH() {
277 if (!SEHCompat || !SXData)
278 return;
279 ArrayRef<uint8_t> A;
280 COFFObj->getSectionContents(SXData, A);
281 if (A.size() % 4 != 0)
282 fatal(".sxdata must be an array of symbol table indices");
283 auto *I = reinterpret_cast<const ulittle32_t *>(A.data());
284 auto *E = reinterpret_cast<const ulittle32_t *>(A.data() + A.size());
285 for (; I != E; ++I)
286 SEHandlers.insert(SparseSymbolBodies[*I]);
287}
288
289MachineTypes ObjectFile::getMachineType() {
290 if (COFFObj)
291 return static_cast<MachineTypes>(COFFObj->getMachine());
292 return IMAGE_FILE_MACHINE_UNKNOWN;
293}
294
295StringRef ltrim1(StringRef S, const char *Chars) {
296 if (!S.empty() && strchr(Chars, S[0]))
297 return S.substr(1);
298 return S;
299}
300
301void ImportFile::parse() {
302 const char *Buf = MB.getBufferStart();
303 const char *End = MB.getBufferEnd();
304 const auto *Hdr = reinterpret_cast<const coff_import_header *>(Buf);
305
306 // Check if the total size is valid.
307 if ((size_t)(End - Buf) != (sizeof(*Hdr) + Hdr->SizeOfData))
308 fatal("broken import library");
309
310 // Read names and create an __imp_ symbol.
311 StringRef Name = Saver.save(StringRef(Buf + sizeof(*Hdr)));
312 StringRef ImpName = Saver.save("__imp_" + Name);
313 const char *NameStart = Buf + sizeof(coff_import_header) + Name.size() + 1;
314 DLLName = StringRef(NameStart);
315 StringRef ExtName;
316 switch (Hdr->getNameType()) {
317 case IMPORT_ORDINAL:
318 ExtName = "";
319 break;
320 case IMPORT_NAME:
321 ExtName = Name;
322 break;
323 case IMPORT_NAME_NOPREFIX:
324 ExtName = ltrim1(Name, "?@_");
325 break;
326 case IMPORT_NAME_UNDECORATE:
327 ExtName = ltrim1(Name, "?@_");
328 ExtName = ExtName.substr(0, ExtName.find('@'));
329 break;
330 }
331
332 this->Hdr = Hdr;
333 ExternalName = ExtName;
334
335 ImpSym = cast<DefinedImportData>(
336 Symtab->addImportData(ImpName, this)->body());
337 if (Hdr->getType() == llvm::COFF::IMPORT_CONST)
338 ConstSym =
339 cast<DefinedImportData>(Symtab->addImportData(Name, this)->body());
340
341 // If type is function, we need to create a thunk which jump to an
342 // address pointed by the __imp_ symbol. (This allows you to call
343 // DLL functions just like regular non-DLL functions.)
344 if (Hdr->getType() != llvm::COFF::IMPORT_CODE)
345 return;
346 ThunkSym = cast<DefinedImportThunk>(
347 Symtab->addImportThunk(Name, ImpSym, Hdr->Machine)->body());
348}
349
350void BitcodeFile::parse() {
351 Obj = check(lto::InputFile::create(MemoryBufferRef(
352 MB.getBuffer(), Saver.save(ParentName + MB.getBufferIdentifier()))));
353 for (const lto::InputFile::Symbol &ObjSym : Obj->symbols()) {
354 StringRef SymName = Saver.save(ObjSym.getName());
355 Symbol *Sym;
356 if (ObjSym.isUndefined()) {
357 Sym = Symtab->addUndefined(SymName, this, false);
358 } else if (ObjSym.isCommon()) {
359 Sym = Symtab->addCommon(this, SymName, ObjSym.getCommonSize());
360 } else if (ObjSym.isWeak() && ObjSym.isIndirect()) {
361 // Weak external.
362 Sym = Symtab->addUndefined(SymName, this, true);
363 std::string Fallback = ObjSym.getCOFFWeakExternalFallback();
364 SymbolBody *Alias = Symtab->addUndefined(Saver.save(Fallback));
365 checkAndSetWeakAlias(Symtab, this, Sym->body(), Alias);
366 } else {
367 bool IsCOMDAT = ObjSym.getComdatIndex() != -1;
368 Sym = Symtab->addRegular(this, SymName, IsCOMDAT);
369 }
370 SymbolBodies.push_back(Sym->body());
371 }
372 Directives = Obj->getCOFFLinkerOpts();
373}
374
375MachineTypes BitcodeFile::getMachineType() {
376 switch (Triple(Obj->getTargetTriple()).getArch()) {
377 case Triple::x86_64:
378 return AMD64;
379 case Triple::x86:
380 return I386;
381 case Triple::arm:
382 return ARMNT;
383 default:
384 return IMAGE_FILE_MACHINE_UNKNOWN;
385 }
386}
387} // namespace coff
388} // namespace lld
389
390// Returns the last element of a path, which is supposed to be a filename.
391static StringRef getBasename(StringRef Path) {
392 size_t Pos = Path.find_last_of("\\/");
393 if (Pos == StringRef::npos)
394 return Path;
395 return Path.substr(Pos + 1);
396}
397
398// Returns a string in the format of "foo.obj" or "foo.obj(bar.lib)".
399std::string lld::toString(coff::InputFile *File) {
400 if (!File)
401 return "(internal)";
402 if (File->ParentName.empty())
403 return File->getName().lower();
404
405 std::string Res =
406 (getBasename(File->ParentName) + "(" + getBasename(File->getName()) + ")")
407 .str();
408 return StringRef(Res).lower();
409}