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