a9ff1ce1b9
GNU ld.bfd supports linking directly against DLLs without using an import library, and some projects have picked up on this habit. (There's no one single unsurmountable issue with using import libraries, but this is a regularly surfacing missing feature.) As long as one is linking by name (instead of by ordinal), the DLL export table contains most of the information needed. (One can inspect what section a symbol points at, to see if it's a function or data symbol. The practical implementation of this loops over all sections for each symbol, but as long as they're not very many, that should hopefully be tolerable performance wise.) One exception where the information in the DLL isn't entirely enough is on i386 with stdcall functions; depending on how they're done, the exported function name can be a plain undecorated name, while the import library would contain the full decorated symbol name. This issue is addressed separately in a different patch. This is implemented mimicing the structure of a regular import library, with one InputFile corresponding to the static archive that just adds lazy symbols, which then are fetched when they are needed. When such a symbol is fetched, we synthesize a coff_import_header structure in memory and create a regular ImportFile out of it. The implementation could be even smaller by just creating ImportFiles for every symbol available immediately, but that would have the drawback of actually ending up importing all symbols unless running with GC enabled (and mingw mode defaults to having it disabled for historical reasons). Differential Revision: https://reviews.llvm.org/D104530
141 lines
4.4 KiB
C++
141 lines
4.4 KiB
C++
//===- 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 "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.
|
|
static std::string maybeDemangleSymbol(StringRef symName) {
|
|
if (config->demangle) {
|
|
std::string prefix;
|
|
StringRef prefixless = symName;
|
|
if (prefixless.consume_front("__imp_"))
|
|
prefix = "__declspec(dllimport) ";
|
|
StringRef demangleInput = prefixless;
|
|
if (config->machine == I386)
|
|
demangleInput.consume_front("_");
|
|
std::string demangled = demangle(std::string(demangleInput));
|
|
if (demangled != demangleInput)
|
|
return prefix + demangle(std::string(demangleInput));
|
|
return (prefix + prefixless).str();
|
|
}
|
|
return std::string(symName);
|
|
}
|
|
std::string toString(coff::Symbol &b) {
|
|
return maybeDemangleSymbol(b.getName());
|
|
}
|
|
std::string toCOFFString(const Archive::Symbol &b) {
|
|
return maybeDemangleSymbol(b.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->wrappedSym->file->thunkLive;
|
|
// Assume any other kind of symbol is live.
|
|
return true;
|
|
}
|
|
|
|
// MinGW specific.
|
|
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));
|
|
}
|
|
|
|
uint16_t DefinedAbsolute::numOutputSections;
|
|
|
|
static Chunk *makeImportThunk(DefinedImportData *s, uint16_t machine) {
|
|
if (machine == AMD64)
|
|
return make<ImportThunkChunkX64>(s);
|
|
if (machine == I386)
|
|
return make<ImportThunkChunkX86>(s);
|
|
if (machine == ARM64)
|
|
return make<ImportThunkChunkARM64>(s);
|
|
assert(machine == ARMNT);
|
|
return make<ImportThunkChunkARM>(s);
|
|
}
|
|
|
|
DefinedImportThunk::DefinedImportThunk(StringRef name, DefinedImportData *s,
|
|
uint16_t machine)
|
|
: Defined(DefinedImportThunkKind, name), wrappedSym(s),
|
|
data(makeImportThunk(s, machine)) {}
|
|
|
|
Defined *Undefined::getWeakAlias() {
|
|
// A weak alias may be a weak alias to another symbol, so check recursively.
|
|
for (Symbol *a = weakAlias; a; a = cast<Undefined>(a)->weakAlias)
|
|
if (auto *d = dyn_cast<Defined>(a))
|
|
return d;
|
|
return nullptr;
|
|
}
|
|
|
|
MemoryBufferRef LazyArchive::getMemberBuffer() {
|
|
Archive::Child c =
|
|
CHECK(sym.getMember(),
|
|
"could not get the member for symbol " + toCOFFString(sym));
|
|
return CHECK(c.getMemoryBufferRef(),
|
|
"could not get the buffer for the member defining symbol " +
|
|
toCOFFString(sym));
|
|
}
|
|
} // namespace coff
|
|
} // namespace lld
|