lld/MachO/SymbolTable.cpp

   1 //===- SymbolTable.cpp ----------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "SymbolTable.h"
  10 #include "InputFiles.h"
  11 #include "Symbols.h"
  12 #include "lld/Common/ErrorHandler.h"
  13 #include "lld/Common/Memory.h"
  14
  15 using namespace llvm;
  16 using namespace lld;
  17 using namespace lld::macho;
  18
  19 Symbol *SymbolTable::find(StringRef name) {
  20   auto it = symMap.find(llvm::CachedHashStringRef(name));
  21   if (it == symMap.end())
  22     return nullptr;
  23   return symVector[it->second];
  24 }
  25
  26 std::pair<Symbol *, bool> SymbolTable::insert(StringRef name) {
  27   auto p = symMap.insert({CachedHashStringRef(name), (int)symVector.size()});
  28
  29   // Name already present in the symbol table.
  30   if (!p.second)
  31     return {symVector[p.first->second], false};
  32
  33   // Name is a new symbol.
  34   Symbol *sym = reinterpret_cast<Symbol *>(make<SymbolUnion>());
  35   symVector.push_back(sym);
  36   return {sym, true};
  37 }
  38
  39 Symbol *SymbolTable::addDefined(StringRef name, InputSection *isec,
  40                                 uint32_t value, bool isWeakDef) {
  41   Symbol *s;
  42   bool wasInserted;
  43   bool overridesWeakDef = false;
  44   std::tie(s, wasInserted) = insert(name);
  45
  46   if (!wasInserted) {
  47     if (auto *defined = dyn_cast<Defined>(s)) {
  48       if (isWeakDef)
  49         return s;
  50       if (!defined->isWeakDef())
  51         error("duplicate symbol: " + name);
  52     } else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
  53       overridesWeakDef = !isWeakDef && dysym->isWeakDef();
  54     }
  55     // Defined symbols take priority over other types of symbols, so in case
  56     // of a name conflict, we fall through to the replaceSymbol() call below.
  57   }
  58
  59   Defined *defined = replaceSymbol<Defined>(s, name, isec, value, isWeakDef,
  60                                             /*isExternal=*/true);
  61   defined->overridesWeakDef = overridesWeakDef;
  62   return s;
  63 }
  64
  65 Symbol *SymbolTable::addUndefined(StringRef name) {
  66   Symbol *s;
  67   bool wasInserted;
  68   std::tie(s, wasInserted) = insert(name);
  69
  70   if (wasInserted)
  71     replaceSymbol<Undefined>(s, name);
  72   else if (LazySymbol *lazy = dyn_cast<LazySymbol>(s))
  73     lazy->fetchArchiveMember();
  74   return s;
  75 }
  76
  77 Symbol *SymbolTable::addCommon(StringRef name, InputFile *file, uint64_t size,
  78                                uint32_t align) {
  79   Symbol *s;
  80   bool wasInserted;
  81   std::tie(s, wasInserted) = insert(name);
  82
  83   if (!wasInserted) {
  84     if (auto *common = dyn_cast<CommonSymbol>(s)) {
  85       if (size < common->size)
  86         return s;
  87     } else if (isa<Defined>(s)) {
  88       return s;
  89     }
  90     // Common symbols take priority over all non-Defined symbols, so in case of
  91     // a name conflict, we fall through to the replaceSymbol() call below.
  92   }
  93
  94   replaceSymbol<CommonSymbol>(s, name, file, size, align);
  95   return s;
  96 }
  97
  98 Symbol *SymbolTable::addDylib(StringRef name, DylibFile *file, bool isWeakDef,
  99                               bool isTlv) {
 100   Symbol *s;
 101   bool wasInserted;
 102   std::tie(s, wasInserted) = insert(name);
 103
 104   if (!wasInserted && isWeakDef)
 105     if (auto *defined = dyn_cast<Defined>(s))
 106       if (!defined->isWeakDef())
 107         defined->overridesWeakDef = true;
 108
 109   if (wasInserted || isa<Undefined>(s) ||
 110       (isa<DylibSymbol>(s) && !isWeakDef && s->isWeakDef()))
 111     replaceSymbol<DylibSymbol>(s, file, name, isWeakDef, isTlv);
 112
 113   return s;
 114 }
 115
 116 Symbol *SymbolTable::addLazy(StringRef name, ArchiveFile *file,
 117                              const llvm::object::Archive::Symbol &sym) {
 118   Symbol *s;
 119   bool wasInserted;
 120   std::tie(s, wasInserted) = insert(name);
 121
 122   if (wasInserted)
 123     replaceSymbol<LazySymbol>(s, file, sym);
 124   else if (isa<Undefined>(s) || (isa<DylibSymbol>(s) && s->isWeakDef()))
 125     file->fetch(sym);
 126   return s;
 127 }
 128
 129 Symbol *SymbolTable::addDSOHandle(const MachHeaderSection *header) {
 130   Symbol *s;
 131   bool wasInserted;
 132   std::tie(s, wasInserted) = insert(DSOHandle::name);
 133   if (!wasInserted) {
 134     // FIXME: Make every symbol (including absolute symbols) contain a
 135     // reference to their originating file, then add that file name to this
 136     // error message.
 137     if (auto *defined = dyn_cast<Defined>(s))
 138       error("found defined symbol with illegal name " + DSOHandle::name);
 139   }
 140   replaceSymbol<DSOHandle>(s, header);
 141   return s;
 142 }
 143
 144 SymbolTable *macho::symtab;