Re: OS/2 and stdarg module

[Andreas Büning]

Eric Blake wrote:
> 
> [Moving from m4-patches to bug-gnulib]
> 
> > > [recommendation to run gnulib-tool]

> > Done. Then the linker complained about 'gl_va_copy' being an unresolved
> > external. Reason is that va_copy is defined to gl_va_copy in config.h.
> > gl_va_copy is supposed to be defined in m4/stdarg.m4. I added gl_STDARG_H
> > manually to configure.ac but this didn't help because the gl_STDARG_H
> > macro in m4/stdarg.m4 uses the AH_VERBATIM macro with an invalid syntax 
> > which
> > results in a noop.
> 
> More details, please.  Adding gl_STDARG_H to configure.ac is wrong; it is 
> already
> added by virtue of the fact that gnulib-tool calls it as part of 
> M4_EARLY/M4_INIT.
> The real question is why ./configure thinks that your compiler doesn't support
> va_copy, and what stdarg.m4 should be sticking into config.h that will
> work for your compiler.

m4/stdarg.m4 contains the following code:

----------------------
    if test $gl_cv_func___va_copy = yes; then
      AC_DEFINE([va_copy], [__va_copy],
        [Define as a macro for copying va_list variables.])
    else
      AH_VERBATIM([#define gl_va_copy(a,b) (a) = (b)])
      AC_DEFINE([va_copy], [gl_va_copy],
        [Define as a macro for copying va_list variables.])
    fi
----------------------

Since $gl_cv_func___va_copy != yes the code after else is executed
and "#define va_copy gl_va_copy" is inserted into config.h. Obviously,
it is intended to also define gl_va_copy in this case but AH_VERBATIM
is called with wrong syntax so that this statement has no effect. 


The autoconf manual says:
----------------------------
 - Macro: AH_VERBATIM (KEY, TEMPLATE)
     Tell `autoheader' to include the TEMPLATE as-is in the header
     template file.  This TEMPLATE is associated with the KEY, which is
     used to sort all the different templates and guarantee their
     uniqueness.  It should be a symbol that can be `AC_DEFINE''d.

     For example:

          AH_VERBATIM([_GNU_SOURCE],
          [/* Enable GNU extensions on systems that have them.  */
          #ifndef _GNU_SOURCE
          # define _GNU_SOURCE
          #endif])
----------------------------

So the second argument to AH_VERBATIM which is _empty_ in this case
is inserted into config.h ==> it's a noop.

Unfortunately, also AH_VERBATIM([_MY_KEY], [#define gl_va_copy(a,b) (a) = (b)])
wouldn't work because (AFAIK) AH_VERBATIM is not expanded at run time (i.e.,
by configure) but at "compile" time, i.e. by autoheader. This means

if bla; then
  AH_VERBATIM(...)
fi

and

AH_VERBATIM(...)
if bla; then
fi

are 100% identical.


Please cc all answers directly to me because I'm not subscribed to the
bug-gnulib mailing list.


Regards,
Andreas