Re: config.guess and $CC

[James Youngman]

On Jan 24, 2008 12:08 AM, Bruno Haible <address@hidden> wrote:
> 3) On MacOS X 10.5 systems, "uname -m" returns "i386". But the system is
> 64-bit, and "gcc -m64" generates x86_64 programs that run perfectly fine
> natively.
>
> A user on such a platform struggled for *hours* to get a program compiled
> with "gcc -m64", because in this situation, config.guess returns no
> indication of a 64-bit CPU:
>
>   address@hidden:~/devel/cln-1.2.0]$ export CC="gcc -m64"
>   address@hidden:~/devel/cln-1.2.0]$ sh autoconf/config.guess
>   i386-apple-darwin9.1.0
>
> If config.guess returns such a result, it is really not obvious that the
> user has to use
>   ./configure --host=x86_64-apple-darwin
> in order to get the program compiled.
>
> Recall that this is a *native* build, not a cross build. I'd say, it's a
> config.guess bug. config.guess should return "i386-apple-darwin9.1.0" if
> the compiler generates 32-bit object code and should return
> "x86_64-apple-darwin9.1.0" if the compiler generates 64-bit object code.

This approach seems eminently rational to me.

1. Systems on which the compiler generates 64-bit code will now appear
to configure scripts as if they are indeed targeting a 64-bit system.
2. The user regains control over what kind of binary to build

Maybe to save diagnostic effort in other quarters we should issue a
warning for the benefit of maintainers when we're overriding the
output of "uname -m".  One could hope that such warning messages would
get included in people's bug reports.  There is an argument for even
issuing a warning of a plan to change the behaviour without actually
channging it yet.  Unfortunately though, the percolation time on new
versions of config.guess is so long that we'd essentially be making
life hard for lots of users for quite a long time, in order to avoid
making life hard for a smaller number of maintainers for less time.

James.