Re: bug formatting a .h function extern declaration with attribute macros

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Eric Blake <[email protected]> writes:

> I'm trying to run indent on the GNU M4 source code base before a
> release (it looks like gnulib added the ability to run make indent
> since the last time I made an m4 release).  But one change that indent
> is insisting on is wrong:
>
> -extern void m4_error (int, int, const char *, ...)
> -  ATTRIBUTE_COLD ATTRIBUTE_FORMAT ((__printf__, 3, 4));
> -extern void m4_error_at_line (int, int, const char *, int, const char *, ...)
> -  ATTRIBUTE_COLD ATTRIBUTE_FORMAT ((__printf__, 5, 6));
> -extern _Noreturn void m4_failure (int, const char *, ...)
> +extern void
> +m4_error (int, int, const char *, ...)
> +     ATTRIBUTE_COLD ATTRIBUTE_FORMAT ((__printf__, 3, 4));
> +     extern void m4_error_at_line (int, int, const char *, int, const char *,
> +                                   ...)
> +     ATTRIBUTE_COLD ATTRIBUTE_FORMAT ((__printf__, 5, 6));
> +     extern _Noreturn void m4_failure (int, const char *, ...)
>
> The old format may be awkward for starting the function name after the
> return type, but even if I break that up, emacs still recommends:
>
> extern void
> m4_error (int, int, const char *, ...)
>   ATTRIBUTE_COLD ATTRIBUTE_FORMAT ((__printf__, 3, 4));
>
> And once indent gets messed up by the double attribute (both
> ATTRIBUTE_COLD and ATTRIBUTE_FORMAT are macros that expand to
> __attribute__ magic; the former without parameters), then the rest of
> the file is messed up (as seen by the four-space indent before the
> next extern function line).  Any ideas on how to tell indent about
> ALL_CAPS macros that fit in attribute positions of declarations?

In GNU Libidn2's idn2.h I do it like this:

# if defined __GNUC__ && defined __GNUC_MINOR__
#  define GCC_VERSION_AT_LEAST(major, minor) ((__GNUC__ > (major)) || (__GNUC__ == (major) && __GNUC_MINOR__ >= (minor)))
# else
#  define GCC_VERSION_AT_LEAST(major, minor) 0
# endif
# if GCC_VERSION_AT_LEAST(2,96)
#  define G_GNUC_IDN2_ATTRIBUTE_PURE __attribute__ ((pure))
# else
#  define G_GNUC_IDN2_ATTRIBUTE_PURE
# endif

  extern _IDN2_API const char *idn2_check_version (const char *req_version)
    G_GNUC_IDN2_ATTRIBUTE_PURE;

GNU Libtasn1 libtasn1.h has some similar usages too.

Not sure if this helps, but maybe this approach could be explored?

I suppose you are familiar with the hack to just disable indent for a
small piece of code too:

  /* *INDENT-OFF* */

extern void
m4_error (int, int, const char *, ...)
  ATTRIBUTE_COLD ATTRIBUTE_FORMAT ((__printf__, 3, 4));

  /* *INDENT-ON* */

/Simon

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