Non-standard types in public header files (was: Re: ssize_t)

[Simon Josefsson]

I realized I couldn't use the ssize_t module directly in GnuTLS.
GnuTLS uses ssize_t in its public header file, so it has this in
configure.ac:

AC_CHECK_TYPE(ssize_t,
DEFINE_SSIZE_T="#include <sys/types.h>"
AC_SUBST(DEFINE_SSIZE_T)
,
AC_DEFINE(NO_SSIZE_T, 1, [no ssize_t type was found])
DEFINE_SSIZE_T="typedef int ssize_t;"
AC_SUBST(DEFINE_SSIZE_T)
,[
#ifdef HAVE_SYS_TYPES_H
# include <sys/types.h>
#endif
#ifdef HAVE_UNISTD_H
# include <unistd.h>
#endif
])

and this in gnutls.h.in:

/* Get ssize_t. */
#ifndef HAVE_SSIZE_T
# define HAVE_SSIZE_T
@DEFINE_SSIZE_T@
#endif

While I appreciate ideas on how to solve this particular problem,
there is a more generic problem here:

I have a similar problem in several packages; in particular for the
?int*_t types.

The gnulib module "stdint" enable applications to use those types
(which I haven't done because it is GPL and my packages are mostly
LGPL...).  However, the module doesn't help if the types are used in
the public API.

I have been successfully using this complex M4 macro:

http://ac-archive.sourceforge.net/guidod/ax_create_stdint_h.html

It create a "foo-int.h" file that I can install on the system, and
that my public header file can include.

Would it be possible to either transform the existing stdint module in
gnulib, or write a new module, that can also support something like
this macro?  Or are there other ideas?

The problem, of course, is that the installed header file cannot
assume a config.h and the HAVE_* stuff.  It should simply work.

A naive implementation of this idea would only work with the same
compiler as the one used when building the package.  Guido's complex
script supposedly handle this, and the generated foo-int.h should
produce correct types by any compilers on the same host (e.g., you can
use both a 32-bit and a 64-bit compiler with the same header file).

I talked with Guido about this earlier, and he seemed positive about
using his stuff in gnulib, although I didn't ask about copyright
assignments.

Thanks.