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
find(StringRef name)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
insert(StringRef name)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
addDefined(StringRef name,InputSection * isec,uint32_t value,bool isWeakDef)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
addUndefined(StringRef name)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
addCommon(StringRef name,InputFile * file,uint64_t size,uint32_t align)77 Symbol *SymbolTable::addCommon(StringRef name, InputFile *file, uint64_t size,
78 uint32_t align) {
79 Symbol *s;
80 bool wasInserted;
81 std::tie(s, wasInserted) = insert(name);
82
83 if (!wasInserted) {
84 if (auto *common = dyn_cast<CommonSymbol>(s)) {
85 if (size < common->size)
86 return s;
87 } else if (isa<Defined>(s)) {
88 return s;
89 }
90 // Common symbols take priority over all non-Defined symbols, so in case of
91 // a name conflict, we fall through to the replaceSymbol() call below.
92 }
93
94 replaceSymbol<CommonSymbol>(s, name, file, size, align);
95 return s;
96 }
97
addDylib(StringRef name,DylibFile * file,bool isWeakDef,bool isTlv)98 Symbol *SymbolTable::addDylib(StringRef name, DylibFile *file, bool isWeakDef,
99 bool isTlv) {
100 Symbol *s;
101 bool wasInserted;
102 std::tie(s, wasInserted) = insert(name);
103
104 if (!wasInserted && isWeakDef)
105 if (auto *defined = dyn_cast<Defined>(s))
106 if (!defined->isWeakDef())
107 defined->overridesWeakDef = true;
108
109 if (wasInserted || isa<Undefined>(s) ||
110 (isa<DylibSymbol>(s) && !isWeakDef && s->isWeakDef()))
111 replaceSymbol<DylibSymbol>(s, file, name, isWeakDef, isTlv);
112
113 return s;
114 }
115
addLazy(StringRef name,ArchiveFile * file,const llvm::object::Archive::Symbol & sym)116 Symbol *SymbolTable::addLazy(StringRef name, ArchiveFile *file,
117 const llvm::object::Archive::Symbol &sym) {
118 Symbol *s;
119 bool wasInserted;
120 std::tie(s, wasInserted) = insert(name);
121
122 if (wasInserted)
123 replaceSymbol<LazySymbol>(s, file, sym);
124 else if (isa<Undefined>(s) || (isa<DylibSymbol>(s) && s->isWeakDef()))
125 file->fetch(sym);
126 return s;
127 }
128
addDSOHandle(const MachHeaderSection * header)129 Symbol *SymbolTable::addDSOHandle(const MachHeaderSection *header) {
130 Symbol *s;
131 bool wasInserted;
132 std::tie(s, wasInserted) = insert(DSOHandle::name);
133 if (!wasInserted) {
134 // FIXME: Make every symbol (including absolute symbols) contain a
135 // reference to their originating file, then add that file name to this
136 // error message.
137 if (isa<Defined>(s))
138 error("found defined symbol with illegal name " + DSOHandle::name);
139 }
140 replaceSymbol<DSOHandle>(s, header);
141 return s;
142 }
143
144 SymbolTable *macho::symtab;
145