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//===- Symbols.cpp --------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "Symbols.h"
#include "COFFLinkerContext.h"
#include "InputFiles.h"
#include "lld/Common/ErrorHandler.h"
#include "lld/Common/Memory.h"
#include "lld/Common/Strings.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Demangle/Demangle.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
using namespace llvm::object;
using namespace lld::coff;
namespace lld {
static_assert(sizeof(SymbolUnion) <= 48,
"symbols should be optimized for memory usage");
// Returns a symbol name for an error message.
std::string maybeDemangleSymbol(const COFFLinkerContext &ctx,
StringRef symName) {
if (ctx.config.demangle) {
std::string prefix;
StringRef prefixless = symName;
if (prefixless.consume_front("__imp_"))
prefix = "__declspec(dllimport) ";
StringRef demangleInput = prefixless;
if (ctx.config.machine == I386)
demangleInput.consume_front("_");
std::string demangled = demangle(demangleInput);
if (demangled != demangleInput)
return prefix + demangled;
return (prefix + prefixless).str();
}
return std::string(symName);
}
std::string toString(const COFFLinkerContext &ctx, coff::Symbol &b) {
return maybeDemangleSymbol(ctx, b.getName());
}
std::string toCOFFString(const COFFLinkerContext &ctx,
const Archive::Symbol &b) {
return maybeDemangleSymbol(ctx, b.getName());
}
const COFFSyncStream &
coff::operator<<(const COFFSyncStream &s,
const llvm::object::Archive::Symbol *sym) {
s << maybeDemangleSymbol(s.ctx, sym->getName());
return s;
}
const COFFSyncStream &coff::operator<<(const COFFSyncStream &s, Symbol *sym) {
return s << maybeDemangleSymbol(s.ctx, sym->getName());
}
namespace coff {
void Symbol::computeName() {
assert(nameData == nullptr &&
"should only compute the name once for DefinedCOFF symbols");
auto *d = cast<DefinedCOFF>(this);
StringRef nameStr =
check(cast<ObjFile>(d->file)->getCOFFObj()->getSymbolName(d->sym));
nameData = nameStr.data();
nameSize = nameStr.size();
assert(nameSize == nameStr.size() && "name length truncated");
}
InputFile *Symbol::getFile() {
if (auto *sym = dyn_cast<DefinedCOFF>(this))
return sym->file;
if (auto *sym = dyn_cast<LazyArchive>(this))
return sym->file;
if (auto *sym = dyn_cast<LazyObject>(this))
return sym->file;
if (auto *sym = dyn_cast<LazyDLLSymbol>(this))
return sym->file;
return nullptr;
}
bool Symbol::isLive() const {
if (auto *r = dyn_cast<DefinedRegular>(this))
return r->getChunk()->live;
if (auto *imp = dyn_cast<DefinedImportData>(this))
return imp->file->live;
if (auto *imp = dyn_cast<DefinedImportThunk>(this))
return imp->getChunk()->live;
// Assume any other kind of symbol is live.
return true;
}
void Symbol::replaceKeepingName(Symbol *other, size_t size) {
StringRef origName = getName();
memcpy(this, other, size);
nameData = origName.data();
nameSize = origName.size();
}
COFFSymbolRef DefinedCOFF::getCOFFSymbol() {
size_t symSize = cast<ObjFile>(file)->getCOFFObj()->getSymbolTableEntrySize();
if (symSize == sizeof(coff_symbol16))
return COFFSymbolRef(reinterpret_cast<const coff_symbol16 *>(sym));
assert(symSize == sizeof(coff_symbol32));
return COFFSymbolRef(reinterpret_cast<const coff_symbol32 *>(sym));
}
uint64_t DefinedAbsolute::getRVA() { return va - ctx.config.imageBase; }
DefinedImportThunk::DefinedImportThunk(COFFLinkerContext &ctx, StringRef name,
DefinedImportData *s,
ImportThunkChunk *chunk)
: Defined(DefinedImportThunkKind, name), wrappedSym(s), data(chunk) {}
Symbol *Undefined::getWeakAlias() {
// A weak alias may be a weak alias to another symbol, so check recursively.
DenseSet<Symbol *> weakChain;
for (Symbol *a = weakAlias; a; a = cast<Undefined>(a)->weakAlias) {
// Anti-dependency symbols can't be chained.
if (a->isAntiDep)
break;
if (!isa<Undefined>(a))
return a;
if (!weakChain.insert(a).second)
break; // We have a cycle.
}
return nullptr;
}
bool Undefined::resolveWeakAlias() {
Defined *d = getDefinedWeakAlias();
if (!d)
return false;
// We want to replace Sym with D. However, we can't just blindly
// copy sizeof(SymbolUnion) bytes from D to Sym because D may be an
// internal symbol, and internal symbols are stored as "unparented"
// Symbols. For that reason we need to check which type of symbol we
// are dealing with and copy the correct number of bytes.
StringRef name = getName();
bool wasAntiDep = isAntiDep;
if (isa<DefinedRegular>(d))
memcpy(this, d, sizeof(DefinedRegular));
else if (isa<DefinedAbsolute>(d))
memcpy(this, d, sizeof(DefinedAbsolute));
else
memcpy(this, d, sizeof(SymbolUnion));
nameData = name.data();
nameSize = name.size();
isAntiDep = wasAntiDep;
return true;
}
MemoryBufferRef LazyArchive::getMemberBuffer() {
Archive::Child c =
CHECK(sym.getMember(), "could not get the member for symbol " +
toCOFFString(file->symtab.ctx, sym));
return CHECK(c.getMemoryBufferRef(),
"could not get the buffer for the member defining symbol " +
toCOFFString(file->symtab.ctx, sym));
}
} // namespace coff
} // namespace lld
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