[Bug c++/107535] New: Shouldn't -fvisibility=hidden hide C++17 inline static variables?

[junchao.zhang at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107535

            Bug ID: 107535
           Summary: Shouldn't -fvisibility=hidden hide C++17 inline static
                    variables?
           Product: gcc
           Version: 11.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: junchao.zhang at gmail dot com
  Target Milestone: ---

I think inline static variables are global. However, they could be hidden by
-fvisibility=hidden.
This is dangerous, since with C++17 inline static variables,  they will appear
in headers and be included in *.cpp files. If the *.cpp files are compiled with
-fvisibility=hidden, each will get their own storage.

$ cat foo.hpp 
struct Foo {static inline int s = 100; };
extern __attribute__ ((visibility ("default"))) void DumpLibFoo();

$ cat foo.cpp
#include <stdio.h>
#include <foo.hpp>
void DumpLibFoo() { printf("In libfoo, Foo::s (%p) = %d\n", &Foo::s, Foo::s); }

$ cat test.cpp
#include <stdio.h>
#include <foo.hpp>

int main() {
  Foo::s = 200;
  printf("In main,   Foo::s (%p) = %d\n", &Foo::s, Foo::s);

  DumpLibFoo();
  return 0;
}

-----
gcc -std=c++17 -c -fPIC -I./ test.cpp -fvisibility=hidden
gcc -std=c++17 -c -fPIC -I./ foo.cpp
gcc -o libfoo.so -shared foo.o
gcc -std=c++17 -o test test.o -Wl,-rpath ./ -L ./ -lfoo

./test
In main,   Foo::s (0x5604c2741010) = 200
In libfoo, Foo::s (0x7f4e5173d028) = 100