Re: Bugs encountered updating GCC

[Daniel Jacobowitz]

On Fri, Sep 12, 2003 at 10:32:06AM -0700, Paul Eggert wrote:
> Daniel Jacobowitz <address@hidden> writes:
> 
> > GCC is built (in bootstrap mode at least, where we know the compiler
> > will be GCC) using -Werror.
> 
> OK.  Then it should be configured with -Werror too.  In general, you
> can't configure with one set of options, and build with a different
> set of options, without running into problems like this.

One of many problems with this is shared config.cache.  Not all
directories can be built with -Werror.  It happens that libiberty does
not use -Werror, and is always configured first, so _that_ finds
malloc.h.  The gcc/ directory hasn't converted to autoconf 2.57 yet,
but it's still being bitten by this change, because of this.

There appears to be no way around this.

> In general, if you're going to use two different compilers in
> different stages of thebuild, you to have to do the equivalent of
> running 'configure' twice.  Once for the native compiler, and once for
> the bootstrap mode where you know the compiler is GCC.  This is
> because the two compilers won't necessarily be compatible.
>
> If I recall correctly, GCC doesn't run 'configure' twice; instead, it
> uses 'configure' to determine the characteristics of the native
> compiler, and then overrides that determination when it knows that it
> is compiling itself.  You can do this with something like the
> following:
> 
> #include <config.h>
> 
> /* Do not include <memory.h> if compiling with GCC, even if 'configure'
>    found it available with the native compiler.  GCC never needs
>    <memory.h>, and since we use -Werror in bootstrap mode, including
>    <memory.h> here might cause a compilation failure.  */
> #ifdef __GNU_C__
> # undef HAVE_MEMORY_H
> #endif

Unless there's a platform where malloc.h is in fact necessary.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer