RE: Bugs encountered updating GCC

[Joseph D. Wagner]

Go to: ftp://alpha.gnu.org/pub/gnu/autoconf/

And download autoconf-2.57a.  Yes, I know it's an alpha version.  Yes, I know 
it hasn't been updated since June 20th.

But I'm not an autoconf developer, so don't blame me.

> -----Original Message-----
> From: Daniel Jacobowitz [mailto:address@hidden
> Sent: Thursday, September 11, 2003 10:49 AM
> To: address@hidden
> Subject: Re: Bugs encountered updating GCC
> 
> On Sun, Sep 07, 2003 at 02:07:51PM -0400, Daniel Jacobowitz wrote:
> > Hi autoconf'ers...
> >
> > I've been involved in converting a number of projects in the GCC and
> sources
> > (binutils, gdb, etc) repositories to autoconf 2.57.  By and large, it's
> > going well, but we've turned up a couple of problems.  I'm not familiar
> with
> > autoconf development, so these may have more historical baggage than I
> know
> > about...
> >
> > The first is with AC_CHECK_HEADERS.  The manual says:
> >    Previous versions of Autoconf merely checked whether the header was
> > accepted by the preprocessor.  This was changed because the old test was
> > inappropriate for typical uses.  Headers are typically used to compile,
> > not merely to preprocess, and the old behavior sometimes accepted
> > headers that clashed at compile-time.
> >
> > However, that's not the whole story.  The old check also failed if there
> > were warning messages on stderr when preprocessing.  The new one doesn't
> do
> > that, by default.  Instead it only does so if ac_c_preproc_warn_flag,
> which
> > is only set if missing headers are a warning rather than an error. As a
> > result autoconf now decides malloc.h is available on FreeBSD, even
> though it
> > has a #warning in it.
> >
> > Test case:
> > foo.h:
> > #warning "A.h"
> >
> > configure.in:
> > AC_INIT(foo.h)
> > AC_CHECK_HEADERS([foo.h])
> > AC_OUTPUT
> >
> > Old output:
> > configure:609: checking for foo.h
> > configure:619: gcc -I/home/drow/autoconf/o/.. -E  conftest.c >/dev/null
> 2>conftest.out
> > In file included from configure:615:
> > /home/drow/autoconf/foo.h:1:2: warning: #warning "A.h"
> > configure: failed program was:
> > #line 614 "configure"
> > #include "confdefs.h"
> > #include <foo.h>
> >
> >
> > configure:2606: checking foo.h usability
> > configure:2619: gcc -I/home/drow/autoconf/o/.. -c -g -O2  conftest.c >&5
> > In file included from configure:2660: /home/drow/autoconf/foo.h:1:2:
> warning: #warning "A.h"
> > configure:2622: $? = 0
> > configure:2625: test -s conftest.o
> > configure:2628: $? = 0
> > configure:2638: result: yes
> > configure:2642: checking foo.h presence
> > configure:2653: gcc -I/home/drow/autoconf/o/.. -E  conftest.c
> > In file included from configure:2662: /home/drow/autoconf/foo.h:1:2:
> warning: #warning "A.h"
> > configure:2659: $? = 0
> > configure:2678: result: yes
> > configure:2714: checking for foo.h
> > configure:2721: result: yes
> 
> Any comments on this?
> 
> I can work around it by conditionally putting -Werror into CPPFLAGS,
> but I don't really like that; I'm not sure what else it might do to
> configure.  Both compiler warnings and errors used to be fatal and now
> neither of them seem to be.
> 
> --
> Daniel Jacobowitz
> MontaVista Software                         Debian GNU/Linux Developer
> 
>