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