Re: build failure, GMP not available

[Mark Mitchell <mark at codesourcery dot com>]

Ian Lance Taylor wrote:
> Mark Mitchell <mark@codesourcery.com> writes:
>
> > I would strongly oppose downloading stuff during the build
> > process. We're not in the apt-get business; we can leave that to the
> > GNU/Linux distributions, the Cygwin distributors, etc.  If you want to
> > build a KDE application, you have to first build/download the KDE
> > libraries; why should GCC be different?
>
> Because gcc is the first step in bringing up a new system. 

I don't find this as persuasive as I used to.  There aren't very many 
new host systems, and when there are, you get started with a cross compiler.

> I disagree: the process of building gcc from a release (as opposed to
> building the development version of gcc) really isn't complicated.
> The only remotely non-standard thing that is required is GNU make.
> Given that, all you need to do is "SRCDIR/configure; make".

OK, I agree: a native compiler, with no special options, isn't too hard. 
 I don't think typing that sequence twice would be too hard either, 
though. :-)

> I'm certainly not saying that we should pull out GMP and MPFR.  But I
> am saying that we need to do much much better about making it easy for
> people to build gcc. 

I agree; I just don't think an external library is the problem.  For 
example, the unfortunate tendency of broken C++ compilers to manifest as 
autoconf errors about "run-time test after link-time failure" (that's 
not the right error) in libstdc++ builds confused me a bunch.  The fact 
that you can pass configure options that are silently ignored is a trap. 
 I'm sure we don't have good documentation for all of the configuration 
options we do have.  The way the libgcc Makefiles get constructed from 
shell scripts and the use of recursive make to invoke them confuses me, 
and the fact that "make" at the top level does things differently than 
"make" in the gcc/ directory also confuses me.  IIRC, --with-cpu= works 
on some systems, but not others.

In other words, the situation that you're on a GNU/Linux system, and 
have to  type "configure; make; make install" several times for several 
packages to GCC doesn't seem too bad to me.  What seems bad, and 
off-putting to newcomers interested in working on the source, is that as 
soon as you get past that point it all gets very tangled very quickly.

But, that's just me.  I wouldn't try to stop anybody from adding 
--with-gmp=http://www.gmp.org/gmp-7.3.tar.gz to the build system, even 
though I'd find it personally frightening. :-)

--
Mark Mitchell
CodeSourcery
mark@codesourcery.com
(650) 331-3385 x713