http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57994
--- Comment #12 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> --- (In reply to Marc Glisse from comment #9) > I believe there are far fewer special cases (and thus > risks) with MPFR, but that would indeed require a suitable testsuite for all > functions for which we enable it (at least if MPFR doesn't already have such > a testsuite, and maybe even then, to make sure we call it properly). MPFR's testsuite is just against the MPFR implementation. These are actually non-regression tests. For comparisons with the functions from the C library, there's mpcheck: https://gforge.inria.fr/projects/mpcheck/ but I don't know whether it includes special values (it wasn't its goal). Note that we tried to follow C99's Annex F when this made sense. MPFR also supports some special functions that are not in ISO C (yet), but may be provided by the C library on some platforms (e.g. Bessel functions, which are also specified in POSIX). Don't forget that the specific rules for signed zeroes are also concerned; again, we tried to follow C99's Annex F, IIRC, even when the specification was rather inconsistent (e.g. under the rounding mode toward negative infinity, the subtraction 1 - 1 returns -0, but log(1) is required to return +0).
