https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61319
--- Comment #10 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Ah. I hope the following will help:
--- a/gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-1.c
+++ b/gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-1.c
@@ -5,6 +5,16 @@
#include <limits.h>
#include "float-cast.h"
+#if !defined LLONG_MAX && defined __LONG_LONG_MAX__
+# define LLONG_MAX __LONG_LONG_MAX__
+#endif
+#if !defined LLONG_MIN && defined __LONG_LONG_MAX__
+# define LLONG_MIN (-__LONG_LONG_MAX__ - 1LL)
+#endif
+#if !defined ULLONG_MAX && defined __LONG_LONG_MAX__
+# define ULLONG_MAX (__LONG_LONG_MAX__ * 2ULL + 1ULL)
+#endif
+
int
main (void)
{
