Re: 2.64, glib and syntax error: unexpected end of file

[Ralf Wildenhues]

Hi Frederic,

* Frederic Peters wrote on Fri, Aug 14, 2009 at 02:02:27PM CEST:
> Building glib fails with autoconf 2.64; ./configure gives out this
> error:
> 
>   checking for GNUC visibility attribute... ./configure: line 31209:
>   syntax error: unexpected end of file

> Anyway I reduced this as best as I could in the attached tarball;
>  autoreconf; ./configure gives expected result with 2.63
> and aborts with the same 'unexpected end of file' with 2.64.

Thank you very much for this reduced test case, it made the analysis
rather easy.  The GLIB_CHECK_COMPILE_WARNINGS macro in your acinclude.m4
file contains:

AS_IF([_AC_EVAL_STDERR($ac_compile) &&
         AC_TRY_COMMAND([(if test -s conftest.err; then false ; else true; 
fi)])],
      [$2],
      [echo "$as_me: failed program was:" >&AS_MESSAGE_LOG_FD
cat conftest.$ac_ext >&AS_MESSAGE_LOG_FD
m4_ifvaln([$3],[$3])dnl])dnl
ac_compile="$glib_ac_compile_save"

and it's the two dnl's that cause the problem, they lead to this
configure code:

  echo "$as_me: failed program was:" >&5
cat conftest.$ac_ext >&5
fiac_compile="$glib_ac_compile_save"

with the "fi" and the next line without intervening space.

Autoconf 2.64 changed AS_IF a bit to be more compact, and to allow
things like
  AS_IF(...) && ...

as documented in NEWS:

  ** The m4sh macros AS_IF and AS_CASE can now be used in shell lists.
     The responsibility for supplying a trailing newline now belongs to
     the call site, but since most users did not add dnl, this generally
     results in fewer empty lines in configure.

As a consequence, you need to remove the last dnl in the m4_ifvaln line.
With 2.63, it will lead to a harmless extra newline in the configure
script.

Cheers,
Ralf