[Bug c++/98105] New: constexpr and unnamed namespace yields relocation R_X86_64_PC32 against undefined symbol ... can not be used when making a shared object; recompile with -fPIC

[Bug c++/98105] New: constexpr and unnamed namespace yields relocation R_X86_64_PC32 against undefined symbol ... can not be used when making a shared object; recompile with -fPIC

[peter_foelsche at mentor dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98105

            Bug ID: 98105
           Summary: constexpr  and unnamed namespace yields relocation
                    R_X86_64_PC32 against undefined symbol ... can not be
                    used when making a shared object; recompile with -fPIC
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: peter_foelsche at mentor dot com
  Target Milestone: ---

Created attachment 49665
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49665&action=edit
g++-10 -std=c++11 2.cxx -shared -fPIC

please compile with

g++-10 -std=c++11 2.cxx -shared -fPIC


This is g++:

g++-10 (Ubuntu 10.2.0-5ubuntu1~20.04) 10.2.0
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

[Bug c++/98105] constexpr and unnamed namespace yields relocation R_X86_64_PC32 against undefined symbol ... can not be used when making a shared object; recompile with -fPIC

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98105

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
           Keywords|                            |wrong-code
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2020-12-03

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
So somehow we are not emitting

namespace
{

class myFactory:public factory
{       public:

       static constexpr LIST s_sList = {
                {1.0, 0}
        };

...
};
}

but I'm not literate enough in C++ to tell if there's a definition missing.

It works with -std=c++17 but not with -std=c++11 or -std=c++14

[Bug c++/98105] constexpr and unnamed namespace yields relocation R_X86_64_PC32 against undefined symbol ... can not be used when making a shared object; recompile with -fPIC

[peter_foelsche at mentor dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98105

--- Comment #2 from Peter Foelsche <peter_foelsche at mentor dot com> ---
sorry -- adding a definition outside of class for the variable solves the
problem!

[Bug c++/98105] constexpr and unnamed namespace yields relocation R_X86_64_PC32 against undefined symbol ... can not be used when making a shared object; recompile with -fPIC

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98105

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Reduced:
```
void f(const int&);

namespace {
  struct myFactory
  {
    static constexpr int s_sList = 1;
  };
}
//constexpr int myFactory::s_sList;
void sdi_register_model()
{
  f(myFactory::s_sList);
}
```

If we uncomment the definition, it works.

I think this is correct behavior, just we should produce a better error message
of not have the definition and only the declaration here.