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                                               const InputFile *file) {
29   auto p = symMap.insert({CachedHashStringRef(name), (int)symVector.size()});
30 
31   Symbol *sym;
32   if (!p.second) {
33     // Name already present in the symbol table.
34     sym = symVector[p.first->second];
35   } else {
36     // Name is a new symbol.
37     sym = reinterpret_cast<Symbol *>(make<SymbolUnion>());
38     symVector.push_back(sym);
39   }
40 
41   sym->isUsedInRegularObj |= !file || isa<ObjFile>(file);
42   return {sym, p.second};
43 }
44 
45 Defined *SymbolTable::addDefined(StringRef name, InputFile *file,
46                                  InputSection *isec, uint64_t value,
47                                  uint64_t size, bool isWeakDef,
48                                  bool isPrivateExtern, bool isThumb) {
49   Symbol *s;
50   bool wasInserted;
51   bool overridesWeakDef = false;
52   std::tie(s, wasInserted) = insert(name, file);
53 
54   if (!wasInserted) {
55     if (auto *defined = dyn_cast<Defined>(s)) {
56       if (isWeakDef) {
57         // Both old and new symbol weak (e.g. inline function in two TUs):
58         // If one of them isn't private extern, the merged symbol isn't.
59         if (defined->isWeakDef())
60           defined->privateExtern &= isPrivateExtern;
61         return defined;
62       }
63       if (!defined->isWeakDef())
64         error("duplicate symbol: " + name + "\n>>> defined in " +
65               toString(defined->getFile()) + "\n>>> defined in " +
66               toString(file));
67     } else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
68       overridesWeakDef = !isWeakDef && dysym->isWeakDef();
69     }
70     // Defined symbols take priority over other types of symbols, so in case
71     // of a name conflict, we fall through to the replaceSymbol() call below.
72   }
73 
74   Defined *defined =
75       replaceSymbol<Defined>(s, name, file, isec, value, size, isWeakDef,
76                              /*isExternal=*/true, isPrivateExtern, isThumb);
77   defined->overridesWeakDef = overridesWeakDef;
78   return defined;
79 }
80 
81 Symbol *SymbolTable::addUndefined(StringRef name, InputFile *file,
82                                   bool isWeakRef) {
83   Symbol *s;
84   bool wasInserted;
85   std::tie(s, wasInserted) = insert(name, file);
86 
87   RefState refState = isWeakRef ? RefState::Weak : RefState::Strong;
88 
89   if (wasInserted)
90     replaceSymbol<Undefined>(s, name, file, refState);
91   else if (auto *lazy = dyn_cast<LazySymbol>(s))
92     lazy->fetchArchiveMember();
93   else if (auto *dynsym = dyn_cast<DylibSymbol>(s))
94     dynsym->refState = std::max(dynsym->refState, refState);
95   else if (auto *undefined = dyn_cast<Undefined>(s))
96     undefined->refState = std::max(undefined->refState, refState);
97   return s;
98 }
99 
100 Symbol *SymbolTable::addCommon(StringRef name, InputFile *file, uint64_t size,
101                                uint32_t align, bool isPrivateExtern) {
102   Symbol *s;
103   bool wasInserted;
104   std::tie(s, wasInserted) = insert(name, file);
105 
106   if (!wasInserted) {
107     if (auto *common = dyn_cast<CommonSymbol>(s)) {
108       if (size < common->size)
109         return s;
110     } else if (isa<Defined>(s)) {
111       return s;
112     }
113     // Common symbols take priority over all non-Defined symbols, so in case of
114     // a name conflict, we fall through to the replaceSymbol() call below.
115   }
116 
117   replaceSymbol<CommonSymbol>(s, name, file, size, align, isPrivateExtern);
118   return s;
119 }
120 
121 Symbol *SymbolTable::addDylib(StringRef name, DylibFile *file, bool isWeakDef,
122                               bool isTlv) {
123   Symbol *s;
124   bool wasInserted;
125   std::tie(s, wasInserted) = insert(name, file);
126 
127   RefState refState = RefState::Unreferenced;
128   if (!wasInserted) {
129     if (auto *defined = dyn_cast<Defined>(s)) {
130       if (isWeakDef && !defined->isWeakDef())
131         defined->overridesWeakDef = true;
132     } else if (auto *undefined = dyn_cast<Undefined>(s)) {
133       refState = undefined->refState;
134     } else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
135       refState = dysym->refState;
136     }
137   }
138 
139   bool isDynamicLookup = file == nullptr;
140   if (wasInserted || isa<Undefined>(s) ||
141       (isa<DylibSymbol>(s) &&
142        ((!isWeakDef && s->isWeakDef()) ||
143         (!isDynamicLookup && cast<DylibSymbol>(s)->isDynamicLookup()))))
144     replaceSymbol<DylibSymbol>(s, file, name, isWeakDef, refState, isTlv);
145 
146   return s;
147 }
148 
149 Symbol *SymbolTable::addDynamicLookup(StringRef name) {
150   return addDylib(name, /*file=*/nullptr, /*isWeakDef=*/false, /*isTlv=*/false);
151 }
152 
153 Symbol *SymbolTable::addLazy(StringRef name, ArchiveFile *file,
154                              const object::Archive::Symbol &sym) {
155   Symbol *s;
156   bool wasInserted;
157   std::tie(s, wasInserted) = insert(name, file);
158 
159   if (wasInserted)
160     replaceSymbol<LazySymbol>(s, file, sym);
161   else if (isa<Undefined>(s) || (isa<DylibSymbol>(s) && s->isWeakDef()))
162     file->fetch(sym);
163   return s;
164 }
165 
166 Defined *SymbolTable::addSynthetic(StringRef name, InputSection *isec,
167                                    uint64_t value, bool isPrivateExtern,
168                                    bool includeInSymtab) {
169   Defined *s = addDefined(name, nullptr, isec, value, /*size=*/0,
170                           /*isWeakDef=*/false, isPrivateExtern,
171                           /*isThumb=*/false);
172   s->includeInSymtab = includeInSymtab;
173   return s;
174 }
175 
176 void lld::macho::treatUndefinedSymbol(const Undefined &sym) {
177   auto message = [](const Undefined &sym) {
178     std::string message = "undefined symbol: " + toString(sym);
179     std::string fileName = toString(sym.getFile());
180     if (!fileName.empty())
181       message += "\n>>> referenced by " + fileName;
182     return message;
183   };
184   switch (config->undefinedSymbolTreatment) {
185   case UndefinedSymbolTreatment::error:
186     error(message(sym));
187     break;
188   case UndefinedSymbolTreatment::warning:
189     warn(message(sym));
190     LLVM_FALLTHROUGH;
191   case UndefinedSymbolTreatment::dynamic_lookup:
192   case UndefinedSymbolTreatment::suppress:
193     symtab->addDynamicLookup(sym.getName());
194     break;
195   case UndefinedSymbolTreatment::unknown:
196     llvm_unreachable("unknown -undefined TREATMENT");
197   }
198 }
199 
200 SymbolTable *macho::symtab;
201