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[llvm-objcopy] Allow strip symtab from executables and DSOs
Differential revision: https://reviews.llvm.org/D61672 llvm-svn: 365193
This commit is contained in:
Eugene Leviant
parent
e7bb9ea3e0
commit
6f9815974b
@ -6,7 +6,7 @@
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FileHeader:
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Class: ELFCLASS64
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Data: ELFDATA2LSB
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Type: ET_EXEC
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Type: ET_REL
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Machine: EM_X86_64
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Sections:
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- Name: .text
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@ -13,7 +13,7 @@
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# BEFORE: Type: PT_LOAD
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# BEFORE-NEXT: Offset: 0x240
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# AFTER: SectionHeaderCount: 5
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# AFTER: SectionHeaderCount: 3
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# AFTER: Type: PT_LOAD
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# AFTER-NEXT: Offset: 0x0
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# AFTER: Type: PT_LOAD
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@ -87,34 +87,6 @@ Sections:
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# CHECK: }
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# CHECK: Section {
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# CHECK: Index: 4
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# CHECK: Name: .symtab
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# CHECK: Type: SHT_SYMTAB (0x2)
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# CHECK: Flags [ (0x0)
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# CHECK: ]
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# CHECK: Address: 0x0
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# CHECK: Offset:
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# CHECK: Size:
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# CHECK: Link: 5
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# CHECK: Info: 1
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# CHECK: AddressAlignment: 8
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# CHECK: EntrySize: 24
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# CHECK: }
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# CHECK: Section {
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# CHECK: Index: 5
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# CHECK: Name: .strtab
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# CHECK: Type: SHT_STRTAB (0x3)
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# CHECK: Flags [ (0x0)
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# CHECK: ]
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# CHECK: Address: 0x0
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# CHECK: Offset:
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# CHECK: Size:
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# CHECK: Link: 0
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# CHECK: Info: 0
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# CHECK: AddressAlignment: 1
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# CHECK: EntrySize: 0
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# CHECK: }
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# CHECK: Section {
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# CHECK: Index: 6
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# CHECK: Name: .shstrtab
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# CHECK: Type: SHT_STRTAB (0x3)
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# CHECK: Flags [ (0x0)
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@ -41,7 +41,7 @@ ProgramHeaders:
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Sections:
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- Section: .text3
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#CHECK: SectionHeaderCount: 6
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#CHECK: SectionHeaderCount: 4
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# CHECK: Sections [
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# CHECK-NEXT: Section {
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@ -92,34 +92,6 @@ ProgramHeaders:
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# CHECK-NEXT: }
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# CHECK-NEXT: Section {
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# CHECK-NEXT: Index: 3
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# CHECK-NEXT: Name: .symtab
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# CHECK-NEXT: Type: SHT_SYMTAB (0x2)
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# CHECK-NEXT: Flags [ (0x0)
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# CHECK-NEXT: ]
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# CHECK-NEXT: Address: 0x0
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# CHECK-NEXT: Offset: 0x3000
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# CHECK-NEXT: Size: 24
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# CHECK-NEXT: Link: 4
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# CHECK-NEXT: Info: 1
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# CHECK-NEXT: AddressAlignment: 8
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# CHECK-NEXT: EntrySize: 24
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# CHECK-NEXT: }
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# CHECK-NEXT: Section {
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# CHECK-NEXT: Index: 4
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# CHECK-NEXT: Name: .strtab
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# CHECK-NEXT: Type: SHT_STRTAB (0x3)
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# CHECK-NEXT: Flags [ (0x0)
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# CHECK-NEXT: ]
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# CHECK-NEXT: Address: 0x0
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# CHECK-NEXT: Offset: 0x3018
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# CHECK-NEXT: Size:
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# CHECK-NEXT: Link: 0
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# CHECK-NEXT: Info: 0
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# CHECK-NEXT: AddressAlignment: 1
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# CHECK-NEXT: EntrySize: 0
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# CHECK-NEXT: }
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# CHECK-NEXT: Section {
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# CHECK-NEXT: Index: 5
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# CHECK-NEXT: Name: .shstrtab
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# CHECK-NEXT: Type: SHT_STRTAB (0x3)
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# CHECK-NEXT: Flags [ (0x0)
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@ -46,7 +46,7 @@ ProgramHeaders:
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# Make sure that when we remove a section we overwrite it with zeros
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# DATA: {{^[^[:blank:]]+}} 00 00 00 00
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#CHECK: SectionHeaderCount: 6
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#CHECK: SectionHeaderCount: 4
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# CHECK: Sections [
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# CHECK: Section {
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@ -97,34 +97,6 @@ ProgramHeaders:
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# CHECK-NEXT: }
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# CHECK-NEXT: Section {
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# CHECK-NEXT: Index: 3
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# CHECK-NEXT: Name: .symtab
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# CHECK-NEXT: Type: SHT_SYMTAB (0x2)
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# CHECK-NEXT: Flags [ (0x0)
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# CHECK-NEXT: ]
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# CHECK-NEXT: Address: 0x0
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# CHECK-NEXT: Offset:
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# CHECK-NEXT: Size:
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# CHECK-NEXT: Link: 4
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# CHECK-NEXT: Info: 1
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# CHECK-NEXT: AddressAlignment: 8
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# CHECK-NEXT: EntrySize: 24
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# CHECK-NEXT: }
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# CHECK-NEXT: Section {
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# CHECK-NEXT: Index: 4
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# CHECK-NEXT: Name: .strtab
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# CHECK-NEXT: Type: SHT_STRTAB (0x3)
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# CHECK-NEXT: Flags [ (0x0)
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# CHECK-NEXT: ]
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# CHECK-NEXT: Address: 0x0
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# CHECK-NEXT: Offset:
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# CHECK-NEXT: Size:
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# CHECK-NEXT: Link: 0
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# CHECK-NEXT: Info: 0
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# CHECK-NEXT: AddressAlignment: 1
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# CHECK-NEXT: EntrySize: 0
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# CHECK-NEXT: }
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# CHECK-NEXT: Section {
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# CHECK-NEXT: Index: 5
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# CHECK-NEXT: Name: .shstrtab
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# CHECK-NEXT: Type: SHT_STRTAB (0x3)
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# CHECK-NEXT: Flags [ (0x0)
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21
test/tools/llvm-objcopy/ELF/strip-unneeded-all-symbols.test
Normal file
21
test/tools/llvm-objcopy/ELF/strip-unneeded-all-symbols.test
Normal file
@ -0,0 +1,21 @@
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## Stripping unneeded symbols from execuatble/DSO should
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## eliminate the static symbol table, because it's not used
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## by the dynamic loader.
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# RUN: yaml2obj %s > %t
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# RUN: cp %t %t1
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# RUN: llvm-objcopy --strip-unneeded %t %t2
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# RUN: llvm-readobj --section-headers %t2 | FileCheck %s
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!ELF
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FileHeader:
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Class: ELFCLASS64
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Data: ELFDATA2LSB
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Type: ET_EXEC
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Machine: EM_X86_64
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Symbols:
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- Name: bar
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- Name: foo
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Binding: STB_GLOBAL
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# CHECK-NOT: .symtab
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@ -423,7 +423,7 @@ static Error updateAndRemoveSymbols(const CopyConfig &Config, Object &Obj) {
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if ((Config.StripUnneeded ||
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is_contained(Config.UnneededSymbolsToRemove, Sym.Name)) &&
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isUnneededSymbol(Sym))
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(!Obj.isRelocatable() || isUnneededSymbol(Sym)))
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return true;
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// We want to remove undefined symbols if all references have been stripped.
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@ -1995,6 +1995,25 @@ template <class ELFT> Error ELFWriter<ELFT>::write() {
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return Buf.commit();
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}
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static Error removeUnneededSections(Object &Obj) {
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// We can remove an empty symbol table from non-relocatable objects.
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// Relocatable objects typically have relocation sections whose
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// sh_link field points to .symtab, so we can't remove .symtab
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// even if it is empty.
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if (Obj.isRelocatable() || Obj.SymbolTable == nullptr ||
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!Obj.SymbolTable->empty())
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return Error::success();
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// .strtab can be used for section names. In such a case we shouldn't
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// remove it.
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auto *StrTab = Obj.SymbolTable->getStrTab() == Obj.SectionNames
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? nullptr
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: Obj.SymbolTable->getStrTab();
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return Obj.removeSections(false, [&](const SectionBase &Sec) {
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return &Sec == Obj.SymbolTable || &Sec == StrTab;
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});
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}
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template <class ELFT> Error ELFWriter<ELFT>::finalize() {
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// It could happen that SectionNames has been removed and yet the user wants
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// a section header table output. We need to throw an error if a user tries
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@ -2004,6 +2023,8 @@ template <class ELFT> Error ELFWriter<ELFT>::finalize() {
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"cannot write section header table because "
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"section header string table was removed");
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if (Error E = removeUnneededSections(Obj))
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return E;
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Obj.sortSections();
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// We need to assign indexes before we perform layout because we need to know
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@ -1051,6 +1051,9 @@ public:
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Segments.emplace_back(llvm::make_unique<Segment>(Data));
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return *Segments.back();
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}
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bool isRelocatable() const {
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return Type != ELF::ET_DYN && Type != ELF::ET_EXEC;
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}
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};
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} // end namespace elf
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