[Bug c++/103291] New: gcc 11 regression with #pragma GCC visibility vs extern inside C++ functions

[Bug c++/103291] New: gcc 11 regression with #pragma GCC visibility vs extern inside C++ functions

[roland at gnu dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103291

            Bug ID: 103291
           Summary: gcc 11 regression with #pragma GCC visibility vs
                    extern inside C++ functions
           Product: gcc
           Version: 11.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: roland at gnu dot org
  Target Milestone: ---

GCC 11 has a regression with:

```
#pragma GCC visibility push(hidden)                                             

int hidden_fetch(void) {                                                        
  extern const int hidden_global;                                               
  return hidden_global;                                                         
}
```

when compiled with -fpic. GCC 10 would always avoid the GOT for this case. GCC
11 avoids the GOT when it's compiled as C, but uses the GOT when it's compiled
as C++. Moving the extern decl outside the function makes it dtrt again in C++
as well.

Reproduced on trunk at 4cdf7db9a39d18bd536d816a5751d4d3cf23808b and on 11
branch at b52e2254b30445f3cd667ae0f0d99b183394e37b.

[Bug c++/103291] [11/12 Regression] visibility is lost for external decls declared inside a function

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103291

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |10.3.0
            Summary|gcc 11 regression with      |[11/12 Regression]
                   |#pragma GCC visibility vs   |visibility is lost for
                   |extern inside C++ functions |external decls declared
                   |                            |inside a function
   Target Milestone|---                         |11.3
      Known to fail|                            |11.1.0, 12.0
           Keywords|                            |missed-optimization

[Bug c++/103291] [11/12 Regression] visibility is lost for external decls declared inside a function

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103291

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-11-16
             Status|UNCONFIRMED                 |NEW
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=102496

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Related to PR 102496 (which was about losing __thread).

Confirmed.

Most likely introduced by the same commit too (r11-3699-g4e62aca0e0).

[Bug c++/103291] [11/12 Regression] #pragma gcc visibility is lost for external decls declared inside a function

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103291

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[11/12 Regression]          |[11/12 Regression] #pragma
                   |visibility is lost for      |gcc visibility is lost for
                   |external decls declared     |external decls declared
                   |inside a function           |inside a function

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The attribute still works.

[Bug c++/103291] [11/12 Regression] #pragma gcc visibility is lost for external decls declared inside a function

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103291

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mpolacek at gcc dot gnu.org

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
> Most likely introduced by the same commit too (r11-3699-g4e62aca0e0).

Yes.  r11-3698:

_Z12hidden_fetchv:
.LFB0:
        pushq   %rbp
.LCFI0:
        movq    %rsp, %rbp
.LCFI1:
        movl    hidden_global(%rip), %eax
        popq    %rbp
.LCFI2:
        ret

r11-3699:

_Z12hidden_fetchv:
.LFB0:
        pushq   %rbp
.LCFI0:
        movq    %rsp, %rbp
.LCFI1:
        movq    hidden_global@GOTPCREL(%rip), %rax
        movl    (%rax), %eax
        popq    %rbp
.LCFI2:
        ret

[Bug c++/103291] [11/12 Regression] #pragma gcc visibility is lost for external decls declared inside a function

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103291

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2

[Bug c++/103291] [11/12 Regression] #pragma gcc visibility is lost for external decls declared inside a function

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103291

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Perhaps determine_visibility could recurse on DECL_LOCAL_DECL_ALIAS if non-NULL
and perhaps DECL_VISIBILITY (decl) != orig_visibility
|| DECL_VISIBILITY_SPECIFIED (decl) != orig_visibility_specified
?  Though, not really sure what should be done if one does e.g.:

int non_hidden_fetch(void) {                                                    
  extern const int hidden_global;                                               
  return hidden_global;                                                         
}

#pragma GCC visibility push(hidden)                                             

int hidden_fetch(void) {                                                        
  extern const int hidden_global;                                               
  return hidden_global;                                                         
}
etc.

[Bug c++/103291] [11/12 Regression] #pragma gcc visibility is lost for external decls declared inside a function

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103291

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |jason at gcc dot gnu.org
                 CC|                            |jason at gcc dot gnu.org
             Status|NEW                         |ASSIGNED

[Bug c++/103291] [11/12 Regression] #pragma gcc visibility is lost for external decls declared inside a function

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103291

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jason Merrill <jason@gcc.gnu.org>:

https://gcc.gnu.org/g:8796eb27e24bd3340ebd393e96a94b91d09407e9

commit r12-7854-g8796eb27e24bd3340ebd393e96a94b91d09407e9
Author: Jason Merrill <jason@redhat.com>
Date:   Sun Mar 27 09:44:59 2022 -0400

    c++: visibility of local extern [PR103291]

    When setting up the hidden namespace-scope decl for a local extern, we also
    need to set its visibility.

            PR c++/103291

    gcc/cp/ChangeLog:

            * name-lookup.cc (push_local_extern_decl_alias): Call
            determine_visibility.

    gcc/testsuite/ChangeLog:

            * g++.dg/ext/visibility/visibility-local-extern1.C: New test.

[Bug c++/103291] [11 Regression] #pragma gcc visibility is lost for external decls declared inside a function

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103291

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jason Merrill
<jason@gcc.gnu.org>:

https://gcc.gnu.org/g:10dcd13ff7a9f0fbbae8749929e8808792c76395

commit r11-9702-g10dcd13ff7a9f0fbbae8749929e8808792c76395
Author: Jason Merrill <jason@redhat.com>
Date:   Sun Mar 27 09:44:59 2022 -0400

    c++: visibility of local extern [PR103291]

    When setting up the hidden namespace-scope decl for a local extern, we also
    need to set its visibility.

            PR c++/103291

    gcc/cp/ChangeLog:

            * name-lookup.c (push_local_extern_decl_alias): Call
            determine_visibility.

    gcc/testsuite/ChangeLog:

            * g++.dg/ext/visibility/visibility-local-extern1.C: New test.

[Bug c++/103291] [11 Regression] #pragma gcc visibility is lost for external decls declared inside a function

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103291

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #7 from Jason Merrill <jason at gcc dot gnu.org> ---
Fixed.