[Bug c/101766] New: Microblaze gcc misses symver but __has_attribute(symver) returns true

[Bug c/101766] New: Microblaze gcc misses symver but __has_attribute(symver) returns true

[giulio.benetti at benettiengineering dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101766

            Bug ID: 101766
           Summary: Microblaze gcc misses symver but
                    __has_attribute(symver) returns true
           Product: gcc
           Version: 10.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: giulio.benetti at benettiengineering dot com
  Target Milestone: ---

Microblaze gcc can't use .symver attribute leading to:
error: symver is only supported on ELF platforms

This is a simple test-case(taken from libfuse3) that reproduce the problem:
'''
# if !__has_attribute (symver)
# error symver attribute not supported
# endif
#else
#error __has_attribute not defined, assume we do not have symver
#endif

__attribute__ ((symver ("fuse_new@FUSE_3.0")))
void func1(void)
{

}

int main(void) {
    return 0;
}

'''
The problem is the discrepancy I've found between __has_attribute(symver)
that return true, while in gcc/gcc/config.gcc 'elfos.h' is not listed under
Microblaze cases. Trying adding elfos.h to it leads to other linker problems
and this makes me think that Microblaze doesn't actually support
__ELF__(symver).
So I thought to build gcc using --disable-symvers explictly until a fix is
found, but that doesn't either work.

Can you please give help?

Thanks a lot!

[Bug c/101766] Microblaze gcc misses symver but __has_attribute(symver) returns true

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101766

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
__has_attribute is broken for many attributes.  If GCC supports them in a
generic way but does not really support them, __has_attribute still returns
true.

[Bug c/101766] Microblaze gcc misses symver but __has_attribute(symver) returns true

[giulio.benetti at benettiengineering dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101766

--- Comment #2 from Giulio Benetti <giulio.benetti at benettiengineering dot com> ---
Ah ok, so the workaround is to check with a little build test, right?

[Bug c/101766] Microblaze gcc misses symver but __has_attribute(symver) returns true

[giulio.benetti at benettiengineering dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101766

--- Comment #3 from Giulio Benetti <giulio.benetti at benettiengineering dot com> ---
I've done this:
https://github.com/libfuse/libfuse/pull/620/commits/3aba09a5c56e017746c5c1652dbc845f4db7374a

and works fine. It doesn't seem to have pitfalls.

[Bug c/101766] Microblaze gcc misses symver but __has_attribute(symver) returns true

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101766

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hjl.tools at gmail dot com

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
*** Bug 102110 has been marked as a duplicate of this bug. ***

[Bug c/101766] Microblaze gcc misses symver but __has_attribute(symver) returns true

[vfazio at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101766

Vincent Fazio <vfazio at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |vfazio at gmail dot com

--- Comment #5 from Vincent Fazio <vfazio at gmail dot com> ---
There's a mail discussion about this topic

https://gcc.gnu.org/pipermail/gcc/2023-March/240834.html

The "easy" route is to just add the proper macro to
config/microblaze/microblaze.h

The more correct, but more arduous, route is "porting" microblaze to correctly
use the elfos.h header and provide the proper overrides in a separate header.

I've tested the former with zero issues and tested a version of the latter and
was able to compile both a kernel and ramfs and successfully boot but doubt all
cases are accounted for. attaching patches for posterity

[Bug c/101766] Microblaze gcc misses symver but __has_attribute(symver) returns true

[vfazio at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101766

--- Comment #6 from Vincent Fazio <vfazio at gmail dot com> ---
Created attachment 54645
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54645&action=edit
add macro to microblaze.h

[Bug c/101766] Microblaze gcc misses symver but __has_attribute(symver) returns true

[vfazio at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101766

--- Comment #7 from Vincent Fazio <vfazio at gmail dot com> ---
Created attachment 54646
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54646&action=edit
partial patch for microblaze migration to elfos.h