On 2025-12-15 09:17, Alejandro Colomar wrote:
I don't see why gnulib would want to have this code:
$ grepc -h -C1 VLA_ELEMS .
#ifdef __STDC_NO_VLA__
# define VLA_ELEMS(n)
#else
# define VLA_ELEMS(n) static n
#endif
Instead of just using
#ifdef __STDC_NO_VLA__
# define VLA_ELEMS(n)
#else
# define VLA_ELEMS(n) n
#endif
plus using __attribute__((__nonnull__())) appropriately.
First, some compilers support [static n] but lack support for
__attribute__((__nonnull__())), and it's useful to port well to these
compilers. One example is Oracle Developer Studio 12.6; I'm sure there
are others.
Second, the VLA_ELEMS notation is shorter and easier to read as-is. For
example, this:
int
main (int argc, char *argv[VLA_ELEMS (argc)])
...
is easier to read than what I think you're proposing:
int ATTRIBUTE_NONNULL ((2))
main (int argc, char *argv[VLA_ELEMS (argc)])
...
Here I am assuming Gnulib vla.h's definition of VLA_ELEMS (which you've
quoted above) along with Gnulib attribute.h plus config.h's definitions,
which are as follows (I have somewhat simplified, but it's still quite a
portability mess, right? No wonder most C software developers run away
from this stuff...):
#if defined __GNUC__ && defined __GNUC_MINOR__ && !defined __clang__
# define _GL_GNUC_PREREQ(major, minor) \
((major) < __GNUC__ + ((minor) <= __GNUC_MINOR__))
#elif defined __clang__
/* clang really only groks GNU C 4.2. */
# define _GL_GNUC_PREREQ(major, minor) \
((major) < 4 + ((minor) <= 2))
#else
# define _GL_GNUC_PREREQ(major, minor) 0
#endif
#if (defined __has_attribute \
&& (!defined __clang_minor__ \
|| (defined __apple_build_version__ \
? 7000000 <= __apple_build_version__ \
: 5 <= __clang_major__)))
# define _GL_HAS_ATTRIBUTE(attr) __has_attribute (__##attr##__)
#else
# define _GL_HAS_ATTRIBUTE(attr) _GL_ATTR_##attr
# define _GL_ATTR_nonnull _GL_GNUC_PREREQ (3, 3)
/* ... */
#endif
#if _GL_HAS_ATTRIBUTE (nonnull)
# define _GL_ATTRIBUTE_NONNULL(args) __attribute__ ((__nonnull__ args))
#else
# define _GL_ATTRIBUTE_NONNULL(args)
#endif
#define ATTRIBUTE_NONNULL(args) _GL_ATTRIBUTE_NONNULL (args)
