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 "InputFiles.h"
11 #include "Symbols.h"
12 #include "lld/Common/ErrorHandler.h"
13 #include "lld/Common/Memory.h"
14 
15 using namespace llvm;
16 using namespace lld;
17 using namespace lld::macho;
18 
19 Symbol *SymbolTable::find(StringRef name) {
20   auto it = symMap.find(llvm::CachedHashStringRef(name));
21   if (it == symMap.end())
22     return nullptr;
23   return symVector[it->second];
24 }
25 
26 std::pair<Symbol *, bool> SymbolTable::insert(StringRef name) {
27   auto p = symMap.insert({CachedHashStringRef(name), (int)symVector.size()});
28 
29   // Name already present in the symbol table.
30   if (!p.second)
31     return {symVector[p.first->second], false};
32 
33   // Name is a new symbol.
34   Symbol *sym = reinterpret_cast<Symbol *>(make<SymbolUnion>());
35   symVector.push_back(sym);
36   return {sym, true};
37 }
38 
39 Symbol *SymbolTable::addDefined(StringRef name, InputSection *isec,
40                                 uint32_t value, bool isWeakDef) {
41   Symbol *s;
42   bool wasInserted;
43   bool overridesWeakDef = false;
44   std::tie(s, wasInserted) = insert(name);
45 
46   if (!wasInserted) {
47     if (auto *defined = dyn_cast<Defined>(s)) {
48       if (isWeakDef)
49         return s;
50       if (!defined->isWeakDef())
51         error("duplicate symbol: " + name);
52     } else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
53       overridesWeakDef = !isWeakDef && dysym->isWeakDef();
54     }
55     // Defined symbols take priority over other types of symbols, so in case
56     // of a name conflict, we fall through to the replaceSymbol() call below.
57   }
58 
59   Defined *defined = replaceSymbol<Defined>(s, name, isec, value, isWeakDef,
60                                             /*isExternal=*/true);
61   defined->overridesWeakDef = overridesWeakDef;
62   return s;
63 }
64 
65 Symbol *SymbolTable::addUndefined(StringRef name) {
66   Symbol *s;
67   bool wasInserted;
68   std::tie(s, wasInserted) = insert(name);
69 
70   if (wasInserted)
71     replaceSymbol<Undefined>(s, name);
72   else if (LazySymbol *lazy = dyn_cast<LazySymbol>(s))
73     lazy->fetchArchiveMember();
74   return s;
75 }
76 
77 Symbol *SymbolTable::addDylib(StringRef name, DylibFile *file, bool isWeakDef,
78                               bool isTlv) {
79   Symbol *s;
80   bool wasInserted;
81   std::tie(s, wasInserted) = insert(name);
82 
83   if (!wasInserted && isWeakDef)
84     if (auto *defined = dyn_cast<Defined>(s))
85       if (!defined->isWeakDef())
86         defined->overridesWeakDef = true;
87 
88   if (wasInserted || isa<Undefined>(s) ||
89       (isa<DylibSymbol>(s) && !isWeakDef && s->isWeakDef()))
90     replaceSymbol<DylibSymbol>(s, file, name, isWeakDef, isTlv);
91 
92   return s;
93 }
94 
95 Symbol *SymbolTable::addLazy(StringRef name, ArchiveFile *file,
96                              const llvm::object::Archive::Symbol &sym) {
97   Symbol *s;
98   bool wasInserted;
99   std::tie(s, wasInserted) = insert(name);
100 
101   if (wasInserted)
102     replaceSymbol<LazySymbol>(s, file, sym);
103   else if (isa<Undefined>(s) || (isa<DylibSymbol>(s) && s->isWeakDef()))
104     file->fetch(sym);
105   return s;
106 }
107 
108 Symbol *SymbolTable::addDSOHandle(const MachHeaderSection *header) {
109   Symbol *s;
110   bool wasInserted;
111   std::tie(s, wasInserted) = insert(DSOHandle::name);
112   if (!wasInserted) {
113     if (auto *defined = dyn_cast<Defined>(s))
114       error("found defined symbol from " + defined->isec->file->getName() +
115             " with illegal name " + DSOHandle::name);
116   }
117   replaceSymbol<DSOHandle>(s, header);
118   return s;
119 }
120 
121 SymbolTable *macho::symtab;
122