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::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 
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 
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 
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 (auto *defined = dyn_cast<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