stdatomic.h broken on GCC-5.4.0 (error: request for member ‘__val’ in something not a structure or union)

stdatomic.h broken on GCC-5.4.0 (error: request for member ‘__val’ in something not a structure or union)

[Joakim Nohlgård]

Dear developers,
The stdatomic.h header included with newlib gives compilation errors
with recent GCC versions.

GCC includes its own stdatomic.h, which works fine, but given that
there are preprocessor conditionals in newlib's stdatomic.h for GCC
makes me believe it has compiled OK at some point.

% printf '%s\n%s' '#include <stdint.h>' '#include <stdatomic.h>' | \
arm-none-eabi-gcc -nostdinc \
-isystem /usr/arm-none-eabi/include \
-isystem /usr/lib/gcc/arm-none-eabi/5.4.0/include \
-x c -o /dev/null -c -

In file included from <stdin>:2:0:
/usr/arm-none-eabi/include/stdatomic.h: In function
‘atomic_flag_test_and_set_explicit’:
/usr/arm-none-eabi/include/stdatomic.h:386:10: error: request for
member ‘__val’ in something not a structure or union
  return (atomic_exchange_explicit(&__object->__flag, 1, __order));
          ^
/usr/arm-none-eabi/include/stdatomic.h: In function
‘atomic_flag_clear_explicit’:
/usr/arm-none-eabi/include/stdatomic.h:393:2: error: request for
member ‘__val’ in something not a structure or union
  atomic_store_explicit(&__object->__flag, 0, __order);
  ^

Building for i686-elf additionally gives errors about argument types:
% printf '%s\n%s' '#include <stdint.h>' '#include <stdatomic.h>' | \
i686-elf-gcc -nostdinc \
-isystem /usr/i686-elf/include \
-isystem /usr/lib/gcc/i686-elf/5.4.0/include \
-x c -o /dev/null -c -

/usr/i686-elf/include/stdatomic.h: In function
‘atomic_flag_test_and_set_explicit’:
/usr/i686-elf/include/stdatomic.h:386:10: error: request for member
‘__val’ in something not a structure or union
  return (atomic_exchange_explicit(&__object->__flag, 1, __order));
          ^
/usr/i686-elf/include/stdatomic.h:386:2: error: incompatible type for
argument 1 of ‘__atomic_exchange_n’
  return (atomic_exchange_explicit(&__object->__flag, 1, __order));
  ^
/usr/i686-elf/include/stdatomic.h: In function ‘atomic_flag_clear_explicit’:
/usr/i686-elf/include/stdatomic.h:393:2: error: request for member
‘__val’ in something not a structure or union
  atomic_store_explicit(&__object->__flag, 0, __order);
  ^
/usr/i686-elf/include/stdatomic.h:393:2: error: incompatible type for
argument 1 of ‘__atomic_store_n’
  atomic_store_explicit(&__object->__flag, 0, __order);
  ^

I have no idea on what would be a proper fix though.

Best regards,
Joakim Nohlgård

Re: stdatomic.h broken on GCC-5.4.0 (error: request for member ‘__val’ in something not a structure or union)

[Sebastian Huber]

This file worked before GCC shipped its own stdatomic.h. You should use 
the GCC provided stdatomic.h. Maybe we should remove the stdatomic.h 
from Newlib.

-- 
Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
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Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.

Re: stdatomic.h broken on GCC-5.4.0 (error: request for member ‘__val’ in something not a structure or union)

[Corinna Vinschen]

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On Feb 23 08:13, Sebastian Huber wrote:
> This file worked before GCC shipped its own stdatomic.h. You should use the
> GCC provided stdatomic.h. Maybe we should remove the stdatomic.h from
> Newlib.

We should continue to provide it for older GCC versions.  We could
do something like

  #if __GNUC_PREREQ__(X,Y)
  #undef _STDATOMIC_H_
  #include_next <stdatomic.h>
  #else
  [rest of our own stdatomic.h]
  #endif

X.Y would be the 1st gcc version providing its own stdatomic.h


Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
Red Hat

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Re: stdatomic.h broken on GCC-5.4.0 (error: request for member ‘__val’ in something not a structure or union)

[Corinna Vinschen]

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On Feb 23 11:17, Corinna Vinschen wrote:
> On Feb 23 08:13, Sebastian Huber wrote:
> > This file worked before GCC shipped its own stdatomic.h. You should use the
> > GCC provided stdatomic.h. Maybe we should remove the stdatomic.h from
> > Newlib.
> 
> We should continue to provide it for older GCC versions.  We could
> do something like
> 
>   #if __GNUC_PREREQ__(X,Y)
>   #undef _STDATOMIC_H_

The undef is apparently not even required.  GCC uses _STDATOMIC_H without
trailing underscore.

>   #include_next <stdatomic.h>
>   #else
>   [rest of our own stdatomic.h]
>   #endif
> 
> X.Y would be the 1st gcc version providing its own stdatomic.h


Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
Red Hat

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