Build Failure: Git 2.50.0-rc0 on NonStop

> Since f93b2a0424 (reftable/basics: introduce `REFTABLE_UNUSED`
> annotation, 2025-02-18), the reftable library was migrated to
> use an internal version of `UNUSED`, which unconditionally sets
> a GNU __attribute__ to avoid warnings function parameters that
> are not being used.
>
> Make the definition conditional to prevent breaking the build
> with non GNU compilers.

> Reported-by: "Randall S. Becker" <rsbecker@nexbridge.com>
> Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
> ---
>  reftable/basics.h | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/reftable/basics.h b/reftable/basics.h
> index d8888c1262..7d22f96261 100644
> --- a/reftable/basics.h
> +++ b/reftable/basics.h
> @@ -16,7 +16,11 @@
>  #include "system.h"
>  #include "reftable-basics.h"
>  
> +#ifdef __GNUC__
>  #define REFTABLE_UNUSED __attribute__((__unused__))
> +#else
> +#define REFTABLE_UNUSED
> +#endif

> Corresponding definition we use in the main part of the project
> defined in compat/posix.h looks like this:
> 
>         #if GIT_GNUC_PREREQ(4, 5)
>         #define UNUSED __attribute__((unused)) \
>                 __attribute__((deprecated ("parameter declared as UNUSED")))
>         #elif defined(__GNUC__)
>         #define UNUSED __attribute__((unused)) \
>                 __attribute__((deprecated))
>         #else
>         #define UNUSED
>         #endif
> 
> GCC 4.5 or older may no longer be relevant, in which case yours may
> be good enough.

> On 2025-05-29 at 16:17:14, Junio C Hamano wrote:
>> Corresponding definition we use in the main part of the project
>> defined in compat/posix.h looks like this:
>> 
>>         #if GIT_GNUC_PREREQ(4, 5)
>>         #define UNUSED __attribute__((unused)) \
>>                 __attribute__((deprecated ("parameter declared as UNUSED")))
>>         #elif defined(__GNUC__)
>>         #define UNUSED __attribute__((unused)) \
>>                 __attribute__((deprecated))
>>         #else
>>         #define UNUSED
>>         #endif
>> 
>> GCC 4.5 or older may no longer be relevant, in which case yours may
>> be good enough.
>
> RHEL 7, which is now well past EOL, had GCC 4.8 and Debian 7, released
> in 2013 and also well past EOL, had GCC 4.7.  I think we can safely
> assume nobody within our support policy is using GCC before 4.5.

> Carlo Marcelo Arenas Belón <carenas@gmail.com> writes:
> 
> > Since f93b2a0424 (reftable/basics: introduce `REFTABLE_UNUSED`
> > annotation, 2025-02-18), the reftable library was migrated to
> > use an internal version of `UNUSED`, which unconditionally sets
> > a GNU __attribute__ to avoid warnings function parameters that
> > are not being used.
> >
> > Make the definition conditional to prevent breaking the build
> > with non GNU compilers.
> 
> Quite a reasonable reasoning.
> 
> > Reported-by: "Randall S. Becker" <rsbecker@nexbridge.com>
> > Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
> > ---
> >  reftable/basics.h | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/reftable/basics.h b/reftable/basics.h
> > index d8888c1262..7d22f96261 100644
> > --- a/reftable/basics.h
> > +++ b/reftable/basics.h
> > @@ -16,7 +16,11 @@
> >  #include "system.h"
> >  #include "reftable-basics.h"
> >  
> > +#ifdef __GNUC__
> >  #define REFTABLE_UNUSED __attribute__((__unused__))
> > +#else
> > +#define REFTABLE_UNUSED
> > +#endif
> 
> Corresponding definition we use in the main part of the project
> defined in compat/posix.h looks like this:
> 
>         #if GIT_GNUC_PREREQ(4, 5)
>         #define UNUSED __attribute__((unused)) \
>                 __attribute__((deprecated ("parameter declared as UNUSED")))
>         #elif defined(__GNUC__)
>         #define UNUSED __attribute__((unused)) \
>                 __attribute__((deprecated))
>         #else
>         #define UNUSED
>         #endif
> 
> GCC 4.5 or older may no longer be relevant, in which case yours may
> be good enough.

> On Fri, May 30, 2025 at 07:35:49AM +0200, Patrick Steinhardt wrote:
> 
> > What I don't understand though: we have a `MAYBE_UNUSED` macro that has
> > the exact same definition in "git-compat-util.h". Why does the macro
> > cause issues in the reftable library, but not over there?
> 
> We turn __attribute__() into a noop for some platforms earlier in
> git-compat-util.h. So it doesn't need a separate #ifdef.

>To: git@vger.kernel.org
>I encountered the following failure of rc0:
>
>static void file_release_data(void *b REFTABLE_UNUSED, struct
>reftable_block_data *dest REFTABLE_UNUSED)
>                                        ^
>"/home/jenkinsbuild/.jenkins/workspace/Git_Pipeline/reftable/blocksource.c"

> On May 28, 2025 2:59 PM, I wrote:
> >To: git@vger.kernel.org
> >I encountered the following failure of rc0:
> >
> >static void file_release_data(void *b REFTABLE_UNUSED, struct
> >reftable_block_data *dest REFTABLE_UNUSED)
> >                                        ^
> >"/home/jenkinsbuild/.jenkins/workspace/Git_Pipeline/reftable/blocksource.c"
> ,
> >line 105: error(112):  expected a ")"
> >
> >
> >I am not at all sure why this is failing at this point. Compiler is c99.
> 
> Looking for help on resolving this before rc1.

>On Fri, May 30, 2025 at 08:04:47AM -0400, rsbecker@nexbridge.com wrote:
>> On May 28, 2025 2:59 PM, I wrote:
>> >To: git@vger.kernel.org
>> >I encountered the following failure of rc0:
>> >
>> >static void file_release_data(void *b REFTABLE_UNUSED, struct
>> >reftable_block_data *dest REFTABLE_UNUSED)
>> >                                        ^
>>
>"/home/jenkinsbuild/.jenkins/workspace/Git_Pipeline/reftable/blocksource.c"
>> ,
>> >line 105: error(112):  expected a ")"
>> >
>> >
>> >I am not at all sure why this is failing at this point. Compiler is c99.
>>
>> Looking for help on resolving this before rc1.
>
>Did you maybe miss the proposed patch at [1]? That should fix your issue.