[ELF] Initialize 2 fields of Symbol in SymbolTable::insert

A new symbol is added to elf::symtab in 3 steps:

1) SymbolTable::insert creates a placeholder.
2) Symbol::mergeProperties
3) Symbol::replace

Fields referenced by steps 2) and 3) should be initialized in
SymbolTable::insert.  `traced` and `referenced` were missed previously.
This did not cause problems because compilers generated code that
initialized them (bit fields) to 0.

Reviewed By: grimar

Differential Revision: https://reviews.llvm.org/D66130

llvm-svn: 368784

2 files changed, 6 insertions, 0 deletions

diff --git a/lld/ELF/SymbolTable.cpp b/lld/ELF/SymbolTable.cpp
index e978e0b8c41..64dd1621cea 100644
--- a/lld/ELF/SymbolTable.cpp
+++ b/lld/ELF/SymbolTable.cpp
@@ -71,6 +71,8 @@ Symbol *SymbolTable::insert(StringRef name) {
   Symbol *sym = reinterpret_cast<Symbol *>(make<SymbolUnion>());
   symVector.push_back(sym);
 
+  // *sym was not initialized by a constructor. Fields that may get referenced
+  // when it is a placeholder must be initialized here.
   sym->setName(name);
   sym->symbolKind = Symbol::PlaceholderKind;
   sym->versionId = VER_NDX_GLOBAL;
@@ -79,6 +81,8 @@ Symbol *SymbolTable::insert(StringRef name) {
   sym->exportDynamic = false;
   sym->inDynamicList = false;
   sym->canInline = true;
+  sym->referenced = false;
+  sym->traced = false;
   sym->scriptDefined = false;
   sym->partition = 1;
   return sym;
diff --git a/lld/ELF/Symbols.h b/lld/ELF/Symbols.h
index 501271010d8..713d8be9e3c 100644
--- a/lld/ELF/Symbols.h
+++ b/lld/ELF/Symbols.h
@@ -537,6 +537,8 @@ void Symbol::replace(const Symbol &newSym) {
   Symbol old = *this;
   memcpy(this, &newSym, newSym.getSymbolSize());
 
+  // old may be a placeholder. The referenced fields must be initialized in
+  // SymbolTable::insert.
   versionId = old.versionId;
   visibility = old.visibility;
   isUsedInRegularObj = old.isUsedInRegularObj;