forked from OSchip/llvm-project
Handle section vs global name conflict.
This is a fix for PR26941. When there is both a section and a global definition with the same name, the global wins. Section symbols are not added to the symbol table; section references are left undefined and fixed up in the object writer unless they've been satisfied by some other definition. llvm-svn: 264649
This commit is contained in:
Evgeniy Stepanov
parent
cc8ee8e3a2
commit
a023f79db1
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@ -96,7 +96,9 @@ namespace llvm {
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DenseMap<std::pair<unsigned, unsigned>, MCSymbol *> LocalSymbols;
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/// Keeps tracks of names that were used both for used declared and
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/// artificial symbols.
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/// artificial symbols. The value is "true" if the name has been used for a
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/// non-section symbol (there can be at most one of those, plus an unlimited
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/// number of section symbols with the same name).
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StringMap<bool, BumpPtrAllocator &> UsedNames;
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/// The next ID to dole out to an unnamed assembler temporary symbol with
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@ -375,9 +375,24 @@ uint64_t ELFObjectWriter::SymbolValue(const MCSymbol &Sym,
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void ELFObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
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const MCAsmLayout &Layout) {
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// Section symbols are used as definitions for undefined symbols with matching
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// names. If there are multiple sections with the same name, the first one is
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// used.
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for (const MCSection &Sec : Asm) {
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const MCSymbol *Begin = Sec.getBeginSymbol();
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if (!Begin)
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continue;
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const MCSymbol *Alias = Asm.getContext().lookupSymbol(Begin->getName());
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if (!Alias || !Alias->isUndefined())
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continue;
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Renames.insert(
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std::make_pair(cast<MCSymbolELF>(Alias), cast<MCSymbolELF>(Begin)));
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}
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// The presence of symbol versions causes undefined symbols and
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// versions declared with @@@ to be renamed.
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for (const MCSymbol &A : Asm.symbols()) {
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const auto &Alias = cast<MCSymbolELF>(A);
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// Not an alias.
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@ -124,19 +124,9 @@ MCSymbolELF *MCContext::getOrCreateSectionSymbol(const MCSectionELF &Section) {
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return Sym;
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StringRef Name = Section.getSectionName();
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MCSymbol *&OldSym = Symbols[Name];
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if (OldSym && OldSym->isUndefined()) {
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Sym = cast<MCSymbolELF>(OldSym);
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return Sym;
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}
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auto NameIter = UsedNames.insert(std::make_pair(Name, true)).first;
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auto NameIter = UsedNames.insert(std::make_pair(Name, false)).first;
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Sym = new (&*NameIter, *this) MCSymbolELF(&*NameIter, /*isTemporary*/ false);
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if (!OldSym)
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OldSym = Sym;
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return Sym;
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}
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@ -192,9 +182,12 @@ MCSymbol *MCContext::createSymbol(StringRef Name, bool AlwaysAddSuffix,
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raw_svector_ostream(NewName) << NextUniqueID++;
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}
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auto NameEntry = UsedNames.insert(std::make_pair(NewName, true));
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if (NameEntry.second) {
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// Ok, we found a name. Have the MCSymbol object itself refer to the copy
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// of the string that is embedded in the UsedNames entry.
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if (NameEntry.second || !NameEntry.first->second) {
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// Ok, we found a name.
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// Mark it as used for a non-section symbol.
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NameEntry.first->second = true;
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// Have the MCSymbol object itself refer to the copy of the string that is
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// embedded in the UsedNames entry.
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return createSymbolImpl(&*NameEntry.first, IsTemporary);
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}
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assert(IsTemporary && "Cannot rename non-temporary symbols");
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@ -1,6 +0,0 @@
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// RUN: not llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o %t.o 2>&1 | FileCheck %s
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.section foo
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foo:
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// CHECK: error: invalid symbol redefinition
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@ -0,0 +1,138 @@
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// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | llvm-readobj -t -r --expand-relocs | FileCheck %s
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// Local symbol overriding section.
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.section x1,"a",@progbits
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.local x1
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.comm x1,4,4
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.long x1 // reloc: .bss + 0
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// Section declared after local. Local symbol wins.
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.local x2
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.comm x2,4,4
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.section x2,"a",@progbits
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.long x2 // reloc: .bss + 4
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// No overriding symbol.
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.section x3,"a",@progbits
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.long x3 // reloc: x3(section) + 0
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// Global vs section.
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.section x4,"a",@progbits
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.long 0
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.globl x4
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.section foo, "a", @progbits
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x4:
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.long 0
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.long x4 // reloc: x4(global) + 0
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// Global vs implicit section
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.globl .data
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.data:
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.long 42
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.long .data // reloc: .data(global) + 0
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// CHECK: Relocations [
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// CHECK: Section (4) .relax1 {
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// CHECK: Relocation {
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// CHECK: Offset: 0x0
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// CHECK: Type: R_X86_64_32 (10)
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// CHECK: Symbol: .bss (3)
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// CHECK: Addend: 0x0
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// CHECK: }
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// CHECK: }
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// CHECK: Section (7) .relax2 {
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// CHECK: Relocation {
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// CHECK: Offset: 0x0
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// CHECK: Type: R_X86_64_32 (10)
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// CHECK: Symbol: .bss (3)
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// CHECK: Addend: 0x4
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// CHECK: }
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// CHECK: }
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// CHECK: Section (9) .relax3 {
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// CHECK: Relocation {
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// CHECK: Offset: 0x0
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// CHECK: Type: R_X86_64_32 (10)
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// CHECK: Symbol: x3 (4)
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// CHECK: Addend: 0x0
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// CHECK: }
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// CHECK: }
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// CHECK: Section (12) .relafoo {
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// CHECK: Relocation {
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// CHECK: Offset: 0x4
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// CHECK: Type: R_X86_64_32 (10)
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// CHECK: Symbol: x4 (6)
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// CHECK: Addend: 0x0
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// CHECK: }
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// CHECK: Relocation {
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// CHECK: Offset: 0xC
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// CHECK: Type: R_X86_64_32 (10)
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// CHECK: Symbol: .data (5)
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// CHECK: Addend: 0x0
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// CHECK: }
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// CHECK: }
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// CHECK: ]
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// CHECK: Symbols [
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// CHECK: Symbol {
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// CHECK: Name: (0)
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// CHECK: Value: 0x0
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// CHECK: Size: 0
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// CHECK: Binding: Local (0x0)
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// CHECK: Type: None (0x0)
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// CHECK: Other: 0
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// CHECK: Section: Undefined (0x0)
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// CHECK: }
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// CHECK: Symbol {
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// CHECK: Name: x1 (67)
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// CHECK: Value: 0x0
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// CHECK: Size: 4
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// CHECK: Binding: Local (0x0)
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// CHECK: Type: Object (0x1)
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// CHECK: Other: 0
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// CHECK: Section: .bss (0x5)
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// CHECK: }
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// CHECK: Symbol {
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// CHECK: Name: x2 (59)
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// CHECK: Value: 0x4
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// CHECK: Size: 4
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// CHECK: Binding: Local (0x0)
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// CHECK: Type: Object (0x1)
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// CHECK: Other: 0
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// CHECK: Section: .bss (0x5)
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// CHECK: }
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// CHECK: Symbol {
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// CHECK: Name: (0)
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// CHECK: Value: 0x0
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// CHECK: Size: 0
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// CHECK: Binding: Local (0x0)
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// CHECK: Type: Section (0x3)
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// CHECK: Other: 0
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// CHECK: Section: .bss (0x5)
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// CHECK: }
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// CHECK: Symbol {
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// CHECK: Name: (0)
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// CHECK: Value: 0x0
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// CHECK: Size: 0
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// CHECK: Binding: Local (0x0)
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// CHECK: Type: Section (0x3)
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// CHECK: Other: 0
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// CHECK: Section: x3 (0x8)
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// CHECK: }
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// CHECK: Symbol {
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// CHECK: Name: .data (37)
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// CHECK: Value: 0x8
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// CHECK: Size: 0
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// CHECK: Binding: Global (0x1)
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// CHECK: Type: None (0x0)
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// CHECK: Other: 0
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// CHECK: Section: foo (0xB)
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// CHECK: }
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// CHECK: Symbol {
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// CHECK: Name: x4 (43)
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// CHECK: Value: 0x0
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// CHECK: Size: 0
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// CHECK: Binding: Global (0x1)
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// CHECK: Type: None (0x0)
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// CHECK: Other: 0
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// CHECK: Section: foo (0xB)
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// CHECK: }
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// CHECK: ]
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