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(StringRef name) {
21   auto it = symMap.find(CachedHashStringRef(name));
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 Symbol *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 s;
56       }
57       if (!defined->isWeakDef()) {
58         error("duplicate symbol: " + name + "\n>>> defined in " +
59               toString(defined->getFile()) + "\n>>> defined in " +
60               toString(file));
61       }
62     } else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
63       overridesWeakDef = !isWeakDef && dysym->isWeakDef();
64     }
65     // Defined symbols take priority over other types of symbols, so in case
66     // of a name conflict, we fall through to the replaceSymbol() call below.
67   }
68 
69   Defined *defined =
70       replaceSymbol<Defined>(s, name, file, isec, value, isWeakDef,
71                              /*isExternal=*/true, isPrivateExtern);
72   defined->overridesWeakDef = overridesWeakDef;
73   return s;
74 }
75 
76 Symbol *SymbolTable::addUndefined(StringRef name, InputFile *file,
77                                   bool isWeakRef) {
78   Symbol *s;
79   bool wasInserted;
80   std::tie(s, wasInserted) = insert(name);
81 
82   auto refState = isWeakRef ? RefState::Weak : RefState::Strong;
83 
84   if (wasInserted)
85     replaceSymbol<Undefined>(s, name, file, refState);
86   else if (auto *lazy = dyn_cast<LazySymbol>(s))
87     lazy->fetchArchiveMember();
88   else if (auto *dynsym = dyn_cast<DylibSymbol>(s))
89     dynsym->refState = std::max(dynsym->refState, refState);
90   else if (auto *undefined = dyn_cast<Undefined>(s))
91     undefined->refState = std::max(undefined->refState, refState);
92   return s;
93 }
94 
95 Symbol *SymbolTable::addCommon(StringRef name, InputFile *file, uint64_t size,
96                                uint32_t align, bool isPrivateExtern) {
97   Symbol *s;
98   bool wasInserted;
99   std::tie(s, wasInserted) = insert(name);
100 
101   if (!wasInserted) {
102     if (auto *common = dyn_cast<CommonSymbol>(s)) {
103       if (size < common->size)
104         return s;
105     } else if (isa<Defined>(s)) {
106       return s;
107     }
108     // Common symbols take priority over all non-Defined symbols, so in case of
109     // a name conflict, we fall through to the replaceSymbol() call below.
110   }
111 
112   replaceSymbol<CommonSymbol>(s, name, file, size, align, isPrivateExtern);
113   return s;
114 }
115 
116 Symbol *SymbolTable::addDylib(StringRef name, DylibFile *file, bool isWeakDef,
117                               bool isTlv) {
118   Symbol *s;
119   bool wasInserted;
120   std::tie(s, wasInserted) = insert(name);
121 
122   auto refState = RefState::Unreferenced;
123   if (!wasInserted) {
124     if (auto *defined = dyn_cast<Defined>(s)) {
125       if (isWeakDef && !defined->isWeakDef())
126         defined->overridesWeakDef = true;
127     } else if (auto *undefined = dyn_cast<Undefined>(s)) {
128       refState = undefined->refState;
129     } else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
130       refState = dysym->refState;
131     }
132   }
133 
134   if (wasInserted || isa<Undefined>(s) ||
135       (isa<DylibSymbol>(s) && !isWeakDef && s->isWeakDef()))
136     replaceSymbol<DylibSymbol>(s, file, name, isWeakDef, refState, isTlv);
137 
138   return s;
139 }
140 
141 Symbol *SymbolTable::addLazy(StringRef name, ArchiveFile *file,
142                              const object::Archive::Symbol &sym) {
143   Symbol *s;
144   bool wasInserted;
145   std::tie(s, wasInserted) = insert(name);
146 
147   if (wasInserted)
148     replaceSymbol<LazySymbol>(s, file, sym);
149   else if (isa<Undefined>(s) || (isa<DylibSymbol>(s) && s->isWeakDef()))
150     file->fetch(sym);
151   return s;
152 }
153 
154 Symbol *SymbolTable::addDSOHandle(const MachHeaderSection *header) {
155   Symbol *s;
156   bool wasInserted;
157   std::tie(s, wasInserted) = insert(DSOHandle::name);
158   if (!wasInserted) {
159     // FIXME: Make every symbol (including absolute symbols) contain a
160     // reference to their originating file, then add that file name to this
161     // error message.
162     if (isa<Defined>(s))
163       error("found defined symbol with illegal name " + DSOHandle::name);
164   }
165   replaceSymbol<DSOHandle>(s, header);
166   return s;
167 }
168 
169 void lld::macho::treatUndefinedSymbol(const Undefined &sym) {
170   std::string message = "undefined symbol: " + toString(sym);
171   std::string fileName = toString(sym.getFile());
172 
173   if (!fileName.empty())
174     message += "\n>>> referenced by " + fileName;
175   switch (config->undefinedSymbolTreatment) {
176   case UndefinedSymbolTreatment::suppress:
177     break;
178   case UndefinedSymbolTreatment::error:
179     error(message);
180     break;
181   case UndefinedSymbolTreatment::warning:
182     warn(message);
183     break;
184   case UndefinedSymbolTreatment::dynamic_lookup:
185     error("dynamic_lookup unimplemented for " + message);
186     break;
187   case UndefinedSymbolTreatment::unknown:
188     llvm_unreachable("unknown -undefined TREATMENT");
189   }
190 }
191 
192 SymbolTable *macho::symtab;
193