On 03/20/2012 10:01 AM, Tristan Gingold wrote:

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 
          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).

Also note that it's not uncommon to have declarations inside of headers, which are not present inside of a library.


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