Re: Patch to specify out-of-tree gdk-pixbuf-csource for cross compiling

[Michael Natterer <mitch gimp org>]

Owen Taylor <otaylor redhat com> writes:

> Sven Neumann <sven gimp org> writes:
> 
> > Hi,
> > 
> > Michael Natterer <mitch gimp org> writes:
> > 
> > > Done. Unfortunately, I noticed that the stuff I did to the configure
> > > scripts won't work...
> > > 
> > > What I did is:
> > > 
> > > AM_CONDITIONAL(CROSS_COMPILING, test $build != $host)
> > > 
> > > if test $CROSS_COMPILING; then
> > >   (...)
> > > 
> > > 
> > > but CROSS_COMPILING expands to CROSS_COMPILING_TRUE and CROSS_COMPILING_FALSE
> > > in the generated configure...
> > > 
> > > The following version would work but looks ugly...
> > > 
> > > AM_CONDITIONAL(CROSS_COMPILING, test $build != $host)
> > > 
> > > if test x$CROSS_COMPILING_FALSE = x; then
> > >   (...)
> > 
> > what about something like this:
> > 
> > if test $build != $host; then
> >   cross_compiling=yes
> > else
> >   cross_compiling=no
> > fi
> > 
> > AM_CONDITIONAL(CROSS_COMPILING, test $cross_compiling = yes)
> > 
> > if test $cross_compiling = yes; then
> >   ...
> > fi
> 
> This is the correct version. The namespace for conditionals is
> completely separate from the namespace for shell variables, and
> no assumption should be made about the implementation of conditionals.

A co-worker just figured out that AC_PROG_CC already sets the shell
variable cross_compiling to either "yes" or "no", so it could be
reduced to:

AM_CONDITIONAL(CROSS_COMPILING, test $cross_compiling = yes)

if test $cross_compiling = yes; then
  ...
fi

However I don't know if this is an implementation detail, as it
appears in the autoconf 2.13 docs but not in the 2.53 ones...

Anyone out there with a definitive answer ?-)

ciao,
--mitch