On 2/16/08, Brian Dessent <brian@xxxxxxxxxxx> wrote: > NightStrike wrote: > > > GCC needs GMP And MPFR. What does it need it for, though? Is it used > > for the build machine, host machine, target machine, or some > > combination thereof? Also, is it needed for all languages? > > They are host libraries and are used to do constant folding and > simplification (and whatever other misc optimizations) in a > host-independent manner. That is, gcc must uphold the notion that the > code generated for a given input and a given target should be identical > no matter whether the compiler is native or a cross, and no matter what > the host of the cross is. Without using these libraries to do those > simplifications, the results might vary based on differences in host > architecture or host precision or host libm bugs or whatnot. They are > needed for gfortran only in 4.2, but for all languages in 4.3. The gcc build system, when building gmp and mpfr in the gcc source tree, will send a --target option to the configure script of gmp and mpfr. If gmp is only used for the host system, why is this? I checked the GMP manual, and I don't think target even applies: [Begin quote] "Note that the `--target' option is not appropriate for GMP. It's for use when building compiler tools, with `--host' being where they will run, and `--target' what they'll produce code for. Ordinary programs or libraries like GMP are only interested in the `--host' part, being where they'll run. (Some past versions of GMP used `--target' incorrectly.)" [End quote] So why does the gcc configure script supply a --target option to configure for mpfr and gmp?
