Index: lld/ELF/Config.h =================================================================== --- lld/ELF/Config.h +++ lld/ELF/Config.h @@ -99,6 +99,7 @@ bool Bsymbolic; bool BsymbolicFunctions; bool ColorDiagnostics = false; + bool DefineCommon; bool Demangle = true; bool DisableVerify; bool EhFrameHdr; Index: lld/ELF/Driver.cpp =================================================================== --- lld/ELF/Driver.cpp +++ lld/ELF/Driver.cpp @@ -498,6 +498,8 @@ Config->Pie = getArg(Args, OPT_pie, OPT_nopie, false); Config->PrintGcSections = Args.hasArg(OPT_print_gc_sections); Config->Relocatable = Args.hasArg(OPT_relocatable); + Config->DefineCommon = getArg(Args, OPT_define_common, OPT_no_define_common, + !Config->Relocatable); Config->Discard = getDiscardOption(Args); Config->SaveTemps = Args.hasArg(OPT_save_temps); Config->SingleRoRx = Args.hasArg(OPT_no_rosegment); Index: lld/ELF/Options.td =================================================================== --- lld/ELF/Options.td +++ lld/ELF/Options.td @@ -45,6 +45,9 @@ def color_diagnostics_eq: J<"color-diagnostics=">, HelpText<"Use colors in diagnostics">; +def define_common: F<"define-common">, + HelpText<"Assign space to common symbols">; + def demangle: F<"demangle">, HelpText<"Demangle symbol names">; def disable_new_dtags: F<"disable-new-dtags">, @@ -134,6 +137,9 @@ def no_color_diagnostics: F<"no-color-diagnostics">, HelpText<"Do not use colors in diagnostics">; +def no_define_common: F<"no-define-common">, + HelpText<"Do not assign space to common symbols">; + def no_demangle: F<"no-demangle">, HelpText<"Do not demangle symbol names">; @@ -265,6 +271,9 @@ def alias_Bstatic_non_shared: F<"non_shared">, Alias; def alias_Bstatic_static: F<"static">, Alias; def alias_L__library_path: J<"library-path=">, Alias; +def alias_define_common_d: Flag<["-"], "d">, Alias; +def alias_define_common_dc: F<"dc">, Alias; +def alias_define_common_dp: F<"dp">, Alias; def alias_discard_all_x: Flag<["-"], "x">, Alias; def alias_discard_locals_X: Flag<["-"], "X">, Alias; def alias_dynamic_list: J<"dynamic-list=">, Alias; @@ -332,7 +341,6 @@ // Options listed below are silently ignored for now for compatibility. def allow_shlib_undefined: F<"allow-shlib-undefined">; def cref: Flag<["--"], "cref">; -def define_common: F<"define-common">; def detect_odr_violations: F<"detect-odr-violations">; def g: Flag<["-"], "g">; def no_add_needed: F<"no-add-needed">; @@ -355,9 +363,6 @@ def Qy : F<"Qy">; // Aliases for ignored options -def alias_define_common_d: Flag<["-"], "d">, Alias; -def alias_define_common_dc: F<"dc">, Alias; -def alias_define_common_dp: F<"dp">, Alias; def alias_version_script_version_script: J<"version-script=">, Alias; Index: lld/ELF/Symbols.cpp =================================================================== --- lld/ELF/Symbols.cpp +++ lld/ELF/Symbols.cpp @@ -73,6 +73,8 @@ return VA; } case SymbolBody::DefinedCommonKind: + if (!Config->DefineCommon) + return 0; return In::Common->OutSec->Addr + In::Common->OutSecOff + cast(Body).Offset; case SymbolBody::SharedKind: { Index: lld/ELF/SyntheticSections.cpp =================================================================== --- lld/ELF/SyntheticSections.cpp +++ lld/ELF/SyntheticSections.cpp @@ -59,6 +59,9 @@ ArrayRef(), "COMMON"); Ret->Live = true; + if (!Config->DefineCommon) + return Ret; + // Sort the common symbols by alignment as an heuristic to pack them better. std::vector Syms = getCommonSymbols(); std::stable_sort(Syms.begin(), Syms.end(), @@ -1154,10 +1157,14 @@ ESym->setVisibility(Body->symbol()->Visibility); ESym->st_value = Body->getVA(); - if (const OutputSectionBase *OutSec = getOutputSection(Body)) + if (const OutputSectionBase *OutSec = getOutputSection(Body)) { ESym->st_shndx = OutSec->SectionIndex; - else if (isa>(Body)) + } else if (isa>(Body)) { ESym->st_shndx = SHN_ABS; + } else if (isa(Body)) { + ESym->st_shndx = SHN_COMMON; + ESym->st_value = cast(Body)->Alignment; + } if (Config->EMachine == EM_MIPS) { // On MIPS we need to mark symbol which has a PLT entry and requires @@ -1189,6 +1196,8 @@ break; } case SymbolBody::DefinedCommonKind: + if (!Config->DefineCommon) + return nullptr; return In::Common->OutSec; case SymbolBody::SharedKind: { auto &SS = cast>(*Sym); Index: lld/test/ELF/relocatable-common.s =================================================================== --- lld/test/ELF/relocatable-common.s +++ lld/test/ELF/relocatable-common.s @@ -0,0 +1,36 @@ +# REQUIRES: x86 +# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t1.o +# RUN: ld.lld -r %t1.o -o %t +# RUN: llvm-readobj -symbols -r %t | FileCheck %s +# RUN: ld.lld -r --no-define-common %t1.o -o %t +# RUN: llvm-readobj -symbols -r %t | FileCheck %s +# RUN: ld.lld -r --define-common %t1.o -o %t +# RUN: llvm-readobj -symbols -r %t | FileCheck -check-prefix=DEFCOMM %s +# RUN: ld.lld -r -d %t1.o -o %t +# RUN: llvm-readobj -symbols -r %t | FileCheck -check-prefix=DEFCOMM %s +# RUN: ld.lld -r -dc %t1.o -o %t +# RUN: llvm-readobj -symbols -r %t | FileCheck -check-prefix=DEFCOMM %s +# RUN: ld.lld -r -dp %t1.o -o %t +# RUN: llvm-readobj -symbols -r %t | FileCheck -check-prefix=DEFCOMM %s + +# CHECK: Symbol { +# CHECK: Name: common (1) +# CHECK-NEXT: Value: 0x4 +# CHECK-NEXT: Size: 4 +# CHECK-NEXT: Binding: Global (0x1) +# CHECK-NEXT: Type: Object (0x1) +# CHECK-NEXT: Other: 0 +# CHECK-NEXT: Section: Common (0xFFF2) +# CHECK-NEXT: } + +# DEFCOMM: Symbol { +# DEFCOMM: Name: common (1) +# DEFCOMM-NEXT: Value: 0x0 +# DEFCOMM-NEXT: Size: 4 +# DEFCOMM-NEXT: Binding: Global (0x1) +# DEFCOMM-NEXT: Type: Object (0x1) +# DEFCOMM-NEXT: Other: 0 +# DEFCOMM-NEXT: Section: COMMON (0x2) +# DEFCOMM-NEXT: } + +.comm common,4,4