On Mar 20, 2012, at 10:56 AM, Ralf Corsepius wrote: > On 03/20/2012 10:01 AM, Tristan Gingold wrote: >> Hi, >> >> I am starting to build fortran for VMS. >> >> The first serious issue was with libgfortran/configure. It checks for >> several math functions, but directly in libm using AC_CHECK_LIB. >> But there is on such things as libm on VMS systems (thus requiring to define >> MATH_LIBRARY as ""). Therefore all these tests fail, >> resulting in a failure during libgfortran build. >> >> I think the best way to test for the math function is to use AC_CHECK_DECLS >> as hinted by the autoconf manual >> (cf the AC_CHECK_DECLS example in >> http://www.gnu.org/software/autoconf/manual/autoconf.html >> AC_CHECK_DECLS([j0], , , [[#include<math.h>]]) >> AC_CHECK_DECLS([[basename(char *)], [dirname(char *)]]) >> >> ) >> but I am not an autoconf expert. >> >> I think that this change makes the AIX specific check for __clog obsolete, >> but I haven't removed it. >> >> With this change I was able to cross build libgfortran for VMS (ia64 and >> alpha). >> I have also bootstrapped gcc for x86_64-darwin, without fortran regressions. >> >> Ok for trunk ? > > IMO, no. > > What you are doing here is to replace checks, which check for presence of a > symbol in a library (e.g. cos in libm.*) by checks for presence of a symbol's > declaration inside of a header. > > This is something entirely different (This also reflects in AC_CHECK_DECL by > default providing HAVE_DECL_XXX defines).
Ah, indeed. I missed that. > Also note that it's not uncommon to have declarations inside of headers, > which are not present inside of a library. So, I should use AC_LINK_IFELSE instead, shouldn't I ? Tristan.