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                                  bool isReferencedDynamically,
50                                  bool noDeadStrip) {
51   Symbol *s;
52   bool wasInserted;
53   bool overridesWeakDef = false;
54   std::tie(s, wasInserted) = insert(name, file);
55 
56   assert(!isWeakDef || (isa<BitcodeFile>(file) && !isec) ||
57          (isa<ObjFile>(file) && file == isec->file));
58 
59   if (!wasInserted) {
60     if (auto *defined = dyn_cast<Defined>(s)) {
61       if (isWeakDef) {
62         if (defined->isWeakDef()) {
63           // Both old and new symbol weak (e.g. inline function in two TUs):
64           // If one of them isn't private extern, the merged symbol isn't.
65           defined->privateExtern &= isPrivateExtern;
66           defined->referencedDynamically |= isReferencedDynamically;
67           defined->noDeadStrip |= noDeadStrip;
68 
69           // FIXME: Handle this for bitcode files.
70           // FIXME: We currently only do this if both symbols are weak.
71           //        We could do this if either is weak (but getting the
72           //        case where !isWeakDef && defined->isWeakDef() right
73           //        requires some care and testing).
74           if (isec)
75             isec->wasCoalesced = true;
76         }
77 
78         return defined;
79       }
80       if (!defined->isWeakDef())
81         error("duplicate symbol: " + name + "\n>>> defined in " +
82               toString(defined->getFile()) + "\n>>> defined in " +
83               toString(file));
84     } else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
85       overridesWeakDef = !isWeakDef && dysym->isWeakDef();
86       dysym->unreference();
87     }
88     // Defined symbols take priority over other types of symbols, so in case
89     // of a name conflict, we fall through to the replaceSymbol() call below.
90   }
91 
92   Defined *defined = replaceSymbol<Defined>(
93       s, name, file, isec, value, size, isWeakDef, /*isExternal=*/true,
94       isPrivateExtern, isThumb, isReferencedDynamically, noDeadStrip);
95   defined->overridesWeakDef = overridesWeakDef;
96   return defined;
97 }
98 
99 Symbol *SymbolTable::addUndefined(StringRef name, InputFile *file,
100                                   bool isWeakRef) {
101   Symbol *s;
102   bool wasInserted;
103   std::tie(s, wasInserted) = insert(name, file);
104 
105   RefState refState = isWeakRef ? RefState::Weak : RefState::Strong;
106 
107   if (wasInserted)
108     replaceSymbol<Undefined>(s, name, file, refState);
109   else if (auto *lazy = dyn_cast<LazySymbol>(s))
110     lazy->fetchArchiveMember();
111   else if (auto *dynsym = dyn_cast<DylibSymbol>(s))
112     dynsym->reference(refState);
113   else if (auto *undefined = dyn_cast<Undefined>(s))
114     undefined->refState = std::max(undefined->refState, refState);
115   return s;
116 }
117 
118 Symbol *SymbolTable::addCommon(StringRef name, InputFile *file, uint64_t size,
119                                uint32_t align, bool isPrivateExtern) {
120   Symbol *s;
121   bool wasInserted;
122   std::tie(s, wasInserted) = insert(name, file);
123 
124   if (!wasInserted) {
125     if (auto *common = dyn_cast<CommonSymbol>(s)) {
126       if (size < common->size)
127         return s;
128     } else if (isa<Defined>(s)) {
129       return s;
130     }
131     // Common symbols take priority over all non-Defined symbols, so in case of
132     // a name conflict, we fall through to the replaceSymbol() call below.
133   }
134 
135   replaceSymbol<CommonSymbol>(s, name, file, size, align, isPrivateExtern);
136   return s;
137 }
138 
139 Symbol *SymbolTable::addDylib(StringRef name, DylibFile *file, bool isWeakDef,
140                               bool isTlv) {
141   Symbol *s;
142   bool wasInserted;
143   std::tie(s, wasInserted) = insert(name, file);
144 
145   RefState refState = RefState::Unreferenced;
146   if (!wasInserted) {
147     if (auto *defined = dyn_cast<Defined>(s)) {
148       if (isWeakDef && !defined->isWeakDef())
149         defined->overridesWeakDef = true;
150     } else if (auto *undefined = dyn_cast<Undefined>(s)) {
151       refState = undefined->refState;
152     } else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
153       refState = dysym->getRefState();
154     }
155   }
156 
157   bool isDynamicLookup = file == nullptr;
158   if (wasInserted || isa<Undefined>(s) ||
159       (isa<DylibSymbol>(s) &&
160        ((!isWeakDef && s->isWeakDef()) ||
161         (!isDynamicLookup && cast<DylibSymbol>(s)->isDynamicLookup())))) {
162     if (auto *dynsym = dyn_cast<DylibSymbol>(s))
163       dynsym->unreference();
164     replaceSymbol<DylibSymbol>(s, file, name, isWeakDef, refState, isTlv);
165   }
166 
167   return s;
168 }
169 
170 Symbol *SymbolTable::addDynamicLookup(StringRef name) {
171   return addDylib(name, /*file=*/nullptr, /*isWeakDef=*/false, /*isTlv=*/false);
172 }
173 
174 Symbol *SymbolTable::addLazy(StringRef name, ArchiveFile *file,
175                              const object::Archive::Symbol &sym) {
176   Symbol *s;
177   bool wasInserted;
178   std::tie(s, wasInserted) = insert(name, file);
179 
180   if (wasInserted)
181     replaceSymbol<LazySymbol>(s, file, sym);
182   else if (isa<Undefined>(s) || (isa<DylibSymbol>(s) && s->isWeakDef()))
183     file->fetch(sym);
184   return s;
185 }
186 
187 Defined *SymbolTable::addSynthetic(StringRef name, InputSection *isec,
188                                    uint64_t value, bool isPrivateExtern,
189                                    bool includeInSymtab,
190                                    bool referencedDynamically) {
191   Defined *s = addDefined(name, nullptr, isec, value, /*size=*/0,
192                           /*isWeakDef=*/false, isPrivateExtern,
193                           /*isThumb=*/false, referencedDynamically,
194                           /*noDeadStrip=*/false);
195   s->includeInSymtab = includeInSymtab;
196   return s;
197 }
198 
199 void lld::macho::treatUndefinedSymbol(const Undefined &sym, StringRef source) {
200   auto message = [source, &sym]() {
201     std::string message = "undefined symbol: " + toString(sym);
202     if (!source.empty())
203       message += "\n>>> referenced by " + source.str();
204     else
205       message += "\n>>> referenced by " + toString(sym.getFile());
206     return message;
207   };
208   switch (config->undefinedSymbolTreatment) {
209   case UndefinedSymbolTreatment::error:
210     error(message());
211     break;
212   case UndefinedSymbolTreatment::warning:
213     warn(message());
214     LLVM_FALLTHROUGH;
215   case UndefinedSymbolTreatment::dynamic_lookup:
216   case UndefinedSymbolTreatment::suppress:
217     symtab->addDynamicLookup(sym.getName());
218     break;
219   case UndefinedSymbolTreatment::unknown:
220     llvm_unreachable("unknown -undefined TREATMENT");
221   }
222 }
223 
224 SymbolTable *macho::symtab;
225