XS build flags

[Gavin Smith]

On Thu, Sep 21, 2023 at 06:06:34PM +0200, Patrice Dumas wrote:
> On Wed, Sep 20, 2023 at 08:44:34PM +0100, Gavin Smith wrote:
> > One change at a time please.  Any gnulib tests should be run
> > with the same compiler flags as used to compile the shared library.
> 
> On that subject, and independently of the main issue of CPPFLAGS, this
> is not what is actually done.  In configure.ac, we have
> 
> LDFLAGS="$PERL_EXT_LDFLAGS $PERL_CONF_ccdlflags $PERL_CONF_cccdlflags"
> 
> In Makefile.am, the equivalent part is (rewritten for brievity)
> 
> AM_LDFLAGS = -avoid-version -module $(PERL_CONF_ccdlflags)
> if HOST_NEEDS_NO_UNDEFINED
>   AM_LDFLAGS += -no-undefined -L$(PERL_INC) $(PERL_CONF_libperl)
> endif
> 
> So, there are additional flags if HOST_NEEDS_NO_UNDEFINED, but there is
> no use of $PERL_CONF_cccdlflags.  According to my reading of the
> documentation, it is actually ok not to have $PERL_CONF_cccdlflags
> in AM_LDFLAGS as it is a CFLAGS, it should be in AM_CFLAGS if it is
> kept (and I think it should), and should in any case be removed from
> configure.ac LDFLAGS.

I see you made some changes to this (on 2023-09-24).

I've just made a further change (121d5104101) to make it clearer that
the same flags are used in both configure.ac and in Makefile.am:

Author: Gavin Smith <gavinsmith0123@gmail.com>
Date:   Mon Nov 20 20:52:51 2023 +0000

    XS build flags
    
    * tp/Texinfo/XS/configure.ac (perl_conf_CFLAGS, perl_conf_LDFLAGS):
    Set and output with AC_SUBST.  Append to CFLAGS and LDFLAGS for
    checks only.
    * tp/Texinfo/XS/Makefile.am: Reuse perl_conf_CFLAGS and
    perl_conf_LDFLAGS.  This makes it clearer that we are adding the
    same flags for building as for configure checks.

We could check if -avoid-version -module should be used for configure
checks too (likewise -no-undefined etc.) and if so, put them in
perl_conf_LDFLAGS the same way.

> There is another inconsistency between Makefile.am and configure.ac,
> in configure.ac CFLAGS is:
> CFLAGS="$PERL_EXT_CFLAGS $PERL_CONF_ccflags"
> 
> In Makefile.am, we have
> AM_CFLAGS = $(PERL_CONF_ccflags) $(PERL_CONF_optimize)
> Such that, to be consistent, in configure.ac CFLAGS should be
> CFLAGS="$PERL_EXT_CFLAGS $PERL_CONF_ccflags $PERL_CONF_optimize"

I think you did this.

> (and also, but it does not seems to me to be important)
> AM_CFLAGS += -DVERSION=\"$(VERSION)\" -DXS_VERSION=\"$(VERSION)\"
> AM_CFLAGS += -I$(PERL_INC)

Possibly not important for the checks, but it could potentially be added
as well if needed (the -I flag may make a difference even if the -D flags
don't).  I see you put this in XSLIBS_CPPFLAGS.  We could have a similar
approach and add an extra variable to pass the extra flags from
configure.ac to Makefile.am.  But I would want to understand whether these
flags might be important for configure checks first.