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
