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 "Config.h"
11 #include "InputFiles.h"
12 #include "Symbols.h"
13 #include "lld/Common/ErrorHandler.h"
14 #include "lld/Common/Memory.h"
15 
16 using namespace llvm;
17 using namespace lld;
18 using namespace lld::macho;
19 
20 Symbol *SymbolTable::find(CachedHashStringRef cachedName) {
21   auto it = symMap.find(cachedName);
22   if (it == symMap.end())
23     return nullptr;
24   return symVector[it->second];
25 }
26 
27 std::pair<Symbol *, bool> SymbolTable::insert(StringRef name) {
28   auto p = symMap.insert({CachedHashStringRef(name), (int)symVector.size()});
29 
30   // Name already present in the symbol table.
31   if (!p.second)
32     return {symVector[p.first->second], false};
33 
34   // Name is a new symbol.
35   Symbol *sym = reinterpret_cast<Symbol *>(make<SymbolUnion>());
36   symVector.push_back(sym);
37   return {sym, true};
38 }
39 
40 Defined *SymbolTable::addDefined(StringRef name, InputFile *file,
41                                  InputSection *isec, uint32_t value,
42                                  bool isWeakDef, bool isPrivateExtern) {
43   Symbol *s;
44   bool wasInserted;
45   bool overridesWeakDef = false;
46   std::tie(s, wasInserted) = insert(name);
47 
48   if (!wasInserted) {
49     if (auto *defined = dyn_cast<Defined>(s)) {
50       if (isWeakDef) {
51         // Both old and new symbol weak (e.g. inline function in two TUs):
52         // If one of them isn't private extern, the merged symbol isn't.
53         if (defined->isWeakDef())
54           defined->privateExtern &= isPrivateExtern;
55         return defined;
56       }
57       if (!defined->isWeakDef())
58         error("duplicate symbol: " + name + "\n>>> defined in " +
59               toString(defined->getFile()) + "\n>>> defined in " +
60               toString(file));
61     } else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
62       overridesWeakDef = !isWeakDef && dysym->isWeakDef();
63     }
64     // Defined symbols take priority over other types of symbols, so in case
65     // of a name conflict, we fall through to the replaceSymbol() call below.
66   }
67 
68   Defined *defined =
69       replaceSymbol<Defined>(s, name, file, isec, value, isWeakDef,
70                              /*isExternal=*/true, isPrivateExtern);
71   defined->overridesWeakDef = overridesWeakDef;
72   return defined;
73 }
74 
75 Symbol *SymbolTable::addUndefined(StringRef name, InputFile *file,
76                                   bool isWeakRef) {
77   Symbol *s;
78   bool wasInserted;
79   std::tie(s, wasInserted) = insert(name);
80 
81   RefState refState = isWeakRef ? RefState::Weak : RefState::Strong;
82 
83   if (wasInserted)
84     replaceSymbol<Undefined>(s, name, file, refState);
85   else if (auto *lazy = dyn_cast<LazySymbol>(s))
86     lazy->fetchArchiveMember();
87   else if (auto *dynsym = dyn_cast<DylibSymbol>(s))
88     dynsym->refState = std::max(dynsym->refState, refState);
89   else if (auto *undefined = dyn_cast<Undefined>(s))
90     undefined->refState = std::max(undefined->refState, refState);
91   return s;
92 }
93 
94 Symbol *SymbolTable::addCommon(StringRef name, InputFile *file, uint64_t size,
95                                uint32_t align, bool isPrivateExtern) {
96   Symbol *s;
97   bool wasInserted;
98   std::tie(s, wasInserted) = insert(name);
99 
100   if (!wasInserted) {
101     if (auto *common = dyn_cast<CommonSymbol>(s)) {
102       if (size < common->size)
103         return s;
104     } else if (isa<Defined>(s)) {
105       return s;
106     }
107     // Common symbols take priority over all non-Defined symbols, so in case of
108     // a name conflict, we fall through to the replaceSymbol() call below.
109   }
110 
111   replaceSymbol<CommonSymbol>(s, name, file, size, align, isPrivateExtern);
112   return s;
113 }
114 
115 Symbol *SymbolTable::addDylib(StringRef name, DylibFile *file, bool isWeakDef,
116                               bool isTlv) {
117   Symbol *s;
118   bool wasInserted;
119   std::tie(s, wasInserted) = insert(name);
120 
121   RefState refState = RefState::Unreferenced;
122   if (!wasInserted) {
123     if (auto *defined = dyn_cast<Defined>(s)) {
124       if (isWeakDef && !defined->isWeakDef())
125         defined->overridesWeakDef = true;
126     } else if (auto *undefined = dyn_cast<Undefined>(s)) {
127       refState = undefined->refState;
128     } else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
129       refState = dysym->refState;
130     }
131   }
132 
133   bool isDynamicLookup = file == nullptr;
134   if (wasInserted || isa<Undefined>(s) ||
135       (isa<DylibSymbol>(s) &&
136        ((!isWeakDef && s->isWeakDef()) ||
137         (!isDynamicLookup && cast<DylibSymbol>(s)->isDynamicLookup()))))
138     replaceSymbol<DylibSymbol>(s, file, name, isWeakDef, refState, isTlv);
139 
140   return s;
141 }
142 
143 Symbol *SymbolTable::addDynamicLookup(StringRef name) {
144   return addDylib(name, /*file=*/nullptr, /*isWeakDef=*/false, /*isTlv=*/false);
145 }
146 
147 Symbol *SymbolTable::addLazy(StringRef name, ArchiveFile *file,
148                              const object::Archive::Symbol &sym) {
149   Symbol *s;
150   bool wasInserted;
151   std::tie(s, wasInserted) = insert(name);
152 
153   if (wasInserted)
154     replaceSymbol<LazySymbol>(s, file, sym);
155   else if (isa<Undefined>(s) || (isa<DylibSymbol>(s) && s->isWeakDef()))
156     file->fetch(sym);
157   return s;
158 }
159 
160 Defined *SymbolTable::addSynthetic(StringRef name, InputSection *isec,
161                                    uint32_t value, bool isPrivateExtern,
162                                    bool isLinkerInternal) {
163   Defined *s = addDefined(name, nullptr, isec, value, /*isWeakDef=*/false,
164                           isPrivateExtern);
165   s->linkerInternal = isLinkerInternal;
166   return s;
167 }
168 
169 void lld::macho::treatUndefinedSymbol(const Undefined &sym) {
170   auto message = [](const Undefined &sym) {
171     std::string message = "undefined symbol: " + toString(sym);
172     std::string fileName = toString(sym.getFile());
173     if (!fileName.empty())
174       message += "\n>>> referenced by " + fileName;
175     return message;
176   };
177   switch (config->undefinedSymbolTreatment) {
178   case UndefinedSymbolTreatment::error:
179     error(message(sym));
180     break;
181   case UndefinedSymbolTreatment::warning:
182     warn(message(sym));
183     LLVM_FALLTHROUGH;
184   case UndefinedSymbolTreatment::dynamic_lookup:
185   case UndefinedSymbolTreatment::suppress:
186     symtab->addDynamicLookup(sym.getName());
187     break;
188   case UndefinedSymbolTreatment::unknown:
189     llvm_unreachable("unknown -undefined TREATMENT");
190   }
191 }
192 
193 SymbolTable *macho::symtab;
194