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From: Jonathan Wakely <jwakely.gcc@gmail.com>
Date: Tue, 24 Nov 2020 20:03:24 +0000
Message-ID: <CAH6eHdROnV7EjbwV6NDG+o6xRzdf0ONQocAnVNRnt9tCKG8Efg@mail.gmail.com>
Subject: Re: Anonymous namespaces and global vs.local symbols in nm output
To: "Kacvinsky, Tom" <Tom.Kacvinsky@vector.com>
Cc: "gcc-help@gcc.gnu.org" <gcc-help@gcc.gnu.org>
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On Tue, 24 Nov 2020 at 19:11, Kacvinsky, Tom via Gcc-help
<gcc-help@gcc.gnu.org> wrote:
>
> This code
>
> #include <string>
> #include <istream>
> #include <iostream>
> #include <vector>
>
> typedef std::vector<unsigned char> Signature;
>
> namespace foo {
>   bool bar (const std::string& input,
>             const Signature& signature,
>             std::istream& key)
>   {
>     return true;
>   }
> }
>
> when compiled with
>
> g++ -fPIC -o global_noans.so -shared -static-libgcc -static-libstdc++ -Wl,-h,global.so -fuse-ld=gold global_noans.cpp
>
> produces this nm output
>
> 0000000000082745 T _ZN3foo3barERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEERKSt6vectorIhSaIhEERSi
>
> Notice how it is a global symbol?
>
> On the other hand, this code#include <string>
> #include <istream>
> #include <iostream>
> #include <vector>
>
> typedef std::vector<unsigned char> Signature;
>
> namespace foo {
>   namespace {
>     bool bar(const std::string& input,
>              const Signature& signature,
>              std::istream& key)
>     {
>       return true;
>     }
>   }
> }
>
> when compiled with
>
> g++ -fPIC -o global.so -shared -static-libgcc -static-libstdc++ -Wl,-h,global.so -fuse-ld=gold global.cpp
>
> produces this nm output
>
> 00000000000826b5 t _ZN3foo12_GLOBAL__N_13barERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEERKSt6vectorIhSaIhEERSi
>
> And now we note the symbolis local.  I tried building the shared library with a -Wl,--version-script=global.map, where global.map
> is set up to make the symbol glocal instead of local, and that did not work.  I also tried compiling the source code with
>
> void __attribute__ ((visibility ("default")))
>
> but that made no difference, either, in the anonymous namespace symbol being lobal.

Why do you want to change it? G++ is doing the right thing.

What are you trying to achieve?