[PATCH] D21607: [ELF] - Proccess 'extern' keyword in version scripts.

[Rafael Espíndola via llvm-commits]

I am not sure it is a good idea to ignore these. 'extern "C++"' forces
the linker to match against mangled names. What is using it in freebsd
and what is it trying to match?

Cheers,
Rafael


On 22 June 2016 at 09:27, George Rimar <grimar at accesssoftek.com> wrote:
> grimar created this revision.
> grimar added reviewers: rafael, ruiu.
> grimar added subscribers: llvm-commits, grimar.
> Herald added a subscriber: emaste.
>
> During investigation about FreeBsd scripts I found that few of them uses
> 'extern' keyword. This patch just reads all globals inside as regular ones.
>
> Note: I downloaded FreeBsd sources and tried to link with every *.map file in batch mode,
> some of them are not script files, so I had to skip them manually.
> Seems that this one in combination with D21556 allows to parse all available
> FreeBsd version scripts.
>
> http://reviews.llvm.org/D21607
>
> Files:
>   ELF/SymbolListFile.cpp
>   test/ELF/version-script-err.s
>   test/ELF/version-script-extern.s
>
> Index: test/ELF/version-script-extern.s
> ===================================================================
> --- test/ELF/version-script-extern.s
> +++ test/ELF/version-script-extern.s
> @@ -0,0 +1,34 @@
> +# REQUIRES: x86
> +
> +# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
> +
> +# RUN: echo "VERSION_1.0{      \
> +# RUN:  extern "C++" {         \
> +# RUN:    foo;                 \
> +# RUN:    "bar";               \
> +# RUN:  };                     \
> +# RUN: }; " > %t1.script
> +# RUN: ld.lld --version-script %t1.script -shared %t.o -o %t.so
> +# RUN: llvm-readobj -dyn-symbols %t.so | FileCheck %s
> +
> +# CHECK: DynamicSymbols [
> +# CHECK:   Symbol {
> +# CHECK:     Name: bar@@VERSION_1.0
> +# CHECK:   }
> +# CHECK:   Symbol {
> +# CHECK:     Name: foo@@VERSION_1.0
> +# CHECK:   }
> +# CHECK:   Symbol {
> +# CHECK:     Name: zed@
> +
> +.global foo
> +.type foo, @function
> +foo:
> +
> +.global bar
> +.type bar, @function
> +bar:
> +
> +.global zed
> +.type zed, @function
> +zed:
> Index: test/ELF/version-script-err.s
> ===================================================================
> --- test/ELF/version-script-err.s
> +++ test/ELF/version-script-err.s
> @@ -8,3 +8,8 @@
>  // RUN: not ld.lld --version-script %terr1.script -shared %t.o -o %t.so 2>&1 | \
>  // RUN:   FileCheck -check-prefix=ERR1 %s
>  // ERR1: unclosed quote
> +
> +// RUN: echo "VERSION { extern "C--" {}; }; " > %terr2.script
> +// RUN: not ld.lld --version-script %terr2.script -shared %t.o -o %t.so 2>&1 | \
> +// RUN:   FileCheck -check-prefix=ERR2 %s
> +// ERR2: unsupported language C-- in extern scope
> Index: ELF/SymbolListFile.cpp
> ===================================================================
> --- ELF/SymbolListFile.cpp
> +++ ELF/SymbolListFile.cpp
> @@ -80,6 +80,7 @@
>    void parseVersion(StringRef Version);
>    void parseLocal();
>    void parseVersionSymbols(StringRef Version);
> +  void parseExtern(StringRef Version);
>  };
>
>  void VersionScriptParser::parseVersion(StringRef Version) {
> @@ -104,6 +105,19 @@
>    Config->VersionScriptGlobalByDefault = false;
>  }
>
> +void VersionScriptParser::parseExtern(StringRef Version) {
> +  expect("extern");
> +  StringRef Lang = next();
> +  if (Lang != "C" && Lang != "C++") {
> +    setError("unsupported language " + Lang + " in extern scope");
> +    return;
> +  }
> +  expect("{");
> +  parseVersionSymbols(Version);
> +  expect("}");
> +  expect(";");
> +}
> +
>  void VersionScriptParser::parseVersionSymbols(StringRef Version) {
>    std::vector<StringRef> *Globals;
>    if (Version.empty()) {
> @@ -117,6 +131,10 @@
>      StringRef Cur = peek();
>      if (Cur == "}" || Cur == "local:" || Error)
>        return;
> +    if (Cur == "extern") {
> +      parseExtern(Version);
> +      continue;
> +    }
>      next();
>      Globals->push_back(Cur);
>      expect(";");
>
>