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//===- SymbolTable.cpp ----------------------------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "SymbolTable.h"
#include "Config.h"
#include "WriterUtils.h"
#include "lld/Common/ErrorHandler.h"
#include "lld/Common/Memory.h"
#include <unordered_set>
#define DEBUG_TYPE "lld"
using namespace llvm;
using namespace lld;
using namespace lld::wasm;
SymbolTable *lld::wasm::Symtab;
void SymbolTable::addFile(InputFile *File) {
log("Processing: " + toString(File));
File->parse();
if (auto *F = dyn_cast<ObjFile>(File))
ObjectFiles.push_back(F);
}
void SymbolTable::reportRemainingUndefines() {
std::unordered_set<Symbol *> Undefs;
for (Symbol *Sym : SymVector) {
if (Sym->isUndefined() && !Sym->isWeak() &&
Config->AllowUndefinedSymbols.count(Sym->getName()) == 0) {
Undefs.insert(Sym);
}
}
if (Undefs.empty())
return;
for (ObjFile *File : ObjectFiles)
for (Symbol *Sym : File->getSymbols())
if (Undefs.count(Sym))
error(toString(File) + ": undefined symbol: " + toString(*Sym));
for (Symbol *Sym : Undefs)
if (!Sym->getFile())
error("undefined symbol: " + toString(*Sym));
}
Symbol *SymbolTable::find(StringRef Name) {
auto It = SymMap.find(CachedHashStringRef(Name));
if (It == SymMap.end())
return nullptr;
return It->second;
}
std::pair<Symbol *, bool> SymbolTable::insert(StringRef Name) {
Symbol *&Sym = SymMap[CachedHashStringRef(Name)];
if (Sym)
return {Sym, false};
Sym = make<Symbol>(Name, false);
SymVector.emplace_back(Sym);
return {Sym, true};
}
void SymbolTable::reportDuplicate(Symbol *Existing, InputFile *NewFile) {
error("duplicate symbol: " + toString(*Existing) + "\n>>> defined in " +
toString(Existing->getFile()) + "\n>>> defined in " +
toString(NewFile));
}
// Get the signature for a given function symbol, either by looking
// it up in function sections (for defined functions), of the imports section
// (for imported functions).
static const WasmSignature *getFunctionSig(const ObjFile &Obj,
const WasmSymbol &Sym) {
DEBUG(dbgs() << "getFunctionSig: " << Sym.Name << "\n");
const WasmObjectFile *WasmObj = Obj.getWasmObj();
return &WasmObj->types()[Sym.FunctionType];
}
// Check the type of new symbol matches that of the symbol is replacing.
// For functions this can also involve verifying that the signatures match.
static void checkSymbolTypes(const Symbol &Existing, const InputFile &F,
const WasmSymbol &New,
const WasmSignature *NewSig) {
if (Existing.isLazy())
return;
bool NewIsFunction = New.Type == WasmSymbol::SymbolType::FUNCTION_EXPORT ||
New.Type == WasmSymbol::SymbolType::FUNCTION_IMPORT;
// First check the symbol types match (i.e. either both are function
// symbols or both are data symbols).
if (Existing.isFunction() != NewIsFunction) {
error("symbol type mismatch: " + New.Name + "\n>>> defined as " +
(Existing.isFunction() ? "Function" : "Global") + " in " +
toString(Existing.getFile()) + "\n>>> defined as " +
(NewIsFunction ? "Function" : "Global") + " in " + F.getName());
return;
}
// For function symbols, optionally check the function signature matches too.
if (!NewIsFunction || !Config->CheckSignatures)
return;
// Skip the signature check if the existing function has no signature (e.g.
// if it is an undefined symbol generated by --undefined command line flag).
if (!Existing.hasFunctionType())
return;
DEBUG(dbgs() << "checkSymbolTypes: " << New.Name << "\n");
assert(NewSig);
const WasmSignature &OldSig = Existing.getFunctionType();
if (*NewSig == OldSig)
return;
error("function signature mismatch: " + New.Name + "\n>>> defined as " +
toString(OldSig) + " in " + toString(Existing.getFile()) +
"\n>>> defined as " + toString(*NewSig) + " in " + F.getName());
}
Symbol *SymbolTable::addDefinedGlobal(StringRef Name) {
DEBUG(dbgs() << "addDefinedGlobal: " << Name << "\n");
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(Name);
if (WasInserted)
S->update(Symbol::DefinedGlobalKind);
else if (!S->isGlobal())
error("symbol type mismatch: " + Name);
return S;
}
Symbol *SymbolTable::addDefined(InputFile *F, const WasmSymbol *Sym,
const InputSegment *Segment) {
DEBUG(dbgs() << "addDefined: " << Sym->Name << "\n");
Symbol *S;
bool WasInserted;
Symbol::Kind Kind = Symbol::DefinedFunctionKind;
const WasmSignature *NewSig = nullptr;
if (Sym->Type == WasmSymbol::SymbolType::GLOBAL_EXPORT)
Kind = Symbol::DefinedGlobalKind;
else
NewSig = getFunctionSig(*cast<ObjFile>(F), *Sym);
std::tie(S, WasInserted) = insert(Sym->Name);
if (WasInserted) {
S->update(Kind, F, Sym, Segment, NewSig);
} else if (S->isLazy()) {
// The existing symbol is lazy. Replace it without checking types since
// lazy symbols don't have any type information.
DEBUG(dbgs() << "replacing existing lazy symbol: " << Sym->Name << "\n");
S->update(Kind, F, Sym, Segment, NewSig);
} else if (!S->isDefined()) {
// The existing symbol table entry is undefined. The new symbol replaces
// it, after checking the type matches
DEBUG(dbgs() << "resolving existing undefined symbol: " << Sym->Name
<< "\n");
checkSymbolTypes(*S, *F, *Sym, NewSig);
S->update(Kind, F, Sym, Segment, NewSig);
} else if (Sym->isWeak()) {
// the new symbol is weak we can ignore it
DEBUG(dbgs() << "existing symbol takes precedence\n");
} else if (S->isWeak()) {
// the new symbol is not weak and the existing symbol is, so we replace
// it
DEBUG(dbgs() << "replacing existing weak symbol\n");
checkSymbolTypes(*S, *F, *Sym, NewSig);
S->update(Kind, F, Sym, Segment, NewSig);
} else {
// neither symbol is week. They conflict.
reportDuplicate(S, F);
}
return S;
}
Symbol *SymbolTable::addUndefinedFunction(StringRef Name,
const WasmSignature *Type) {
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(Name);
if (WasInserted) {
S->update(Symbol::UndefinedFunctionKind, nullptr, nullptr, nullptr, Type);
} else if (!S->isFunction()) {
error("symbol type mismatch: " + Name);
}
return S;
}
Symbol *SymbolTable::addUndefined(InputFile *F, const WasmSymbol *Sym) {
DEBUG(dbgs() << "addUndefined: " << Sym->Name << "\n");
Symbol *S;
bool WasInserted;
Symbol::Kind Kind = Symbol::UndefinedFunctionKind;
const WasmSignature *NewSig = nullptr;
if (Sym->Type == WasmSymbol::SymbolType::GLOBAL_IMPORT)
Kind = Symbol::UndefinedGlobalKind;
else
NewSig = getFunctionSig(*cast<ObjFile>(F), *Sym);
std::tie(S, WasInserted) = insert(Sym->Name);
if (WasInserted) {
S->update(Kind, F, Sym, nullptr, NewSig);
} else if (S->isLazy()) {
DEBUG(dbgs() << "resolved by existing lazy\n");
auto *AF = cast<ArchiveFile>(S->getFile());
AF->addMember(&S->getArchiveSymbol());
} else if (S->isDefined()) {
DEBUG(dbgs() << "resolved by existing\n");
checkSymbolTypes(*S, *F, *Sym, NewSig);
}
return S;
}
void SymbolTable::addLazy(ArchiveFile *F, const Archive::Symbol *Sym) {
DEBUG(dbgs() << "addLazy: " << Sym->getName() << "\n");
StringRef Name = Sym->getName();
Symbol *S;
bool WasInserted;
std::tie(S, WasInserted) = insert(Name);
if (WasInserted) {
S->update(Symbol::LazyKind, F);
S->setArchiveSymbol(*Sym);
} else if (S->isUndefined()) {
// There is an existing undefined symbol. The can load from the
// archive.
DEBUG(dbgs() << "replacing existing undefined\n");
F->addMember(Sym);
}
}
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