AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
AC_CHECK_DECLS([isfinite], , , [#include <math.h>])
if test "$ac_cv_have_decl_isfinite" = yes; then
AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
AC_CHECK_DECLS([isfinite], , , [#include <math.h>])
if test "$ac_cv_have_decl_isfinite" = yes; then