diff --git a/m4/virt-compile-warnings.m4 b/m4/virt-compile-warnings.m4 index fa0940fc6885696e68dd79f801fb2730c01f6721..7b56115ce69f08e8798b40d79e38869b08849ae8 100644 --- a/m4/virt-compile-warnings.m4 +++ b/m4/virt-compile-warnings.m4 @@ -134,6 +134,24 @@ AC_DEFUN([LIBVIRT_COMPILE_WARNINGS],[ [lv_cv_gcc_wlogical_op_equal_expr_broken=yes]) CFLAGS="$save_CFLAGS"]) + AC_CACHE_CHECK([whether clang gives bogus warnings for -Wdouble-promotion], + [lv_cv_clang_double_promotion_broken], [ + save_CFLAGS="$CFLAGS" + CFLAGS="-O2 -Wdouble-promotion -Werror" + AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[ + #include + ]], [[ + float f = 0.0; + return isnan(f);]])], + [lv_cv_clang_double_promotion_broken=no], + [lv_cv_clang_double_promotion_broken=yes]) + CFLAGS="$save_CFLAGS"]) + + if test "$lv_cv_clang_double_promotion_broken" = "yes"; + then + dontwarn="$dontwarn -Wdouble-promotion" + fi + # We might fundamentally need some of these disabled forever, but # ideally we'd turn many of them on dontwarn="$dontwarn -Wfloat-equal"