use of stdckdint.h

C23 is going to have this header.  The industry is already moving
towards accepting it; OSes and compilers started to implement theirs.

Why not detect its presence and if any, prefer over other ways.

See also:

- https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2683.pdf
- https://reviews.freebsd.org/D41734
- https://reviews.llvm.org/D157331
- https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=8441841a1b985d68245954af1ff023db121b0635

1 files changed, 3 insertions, 0 deletions

diff --git a/gc.c b/gc.c
index 41207b6eb2..59201458f1 100644
--- a/gc.c
+++ b/gc.c
@@ -224,6 +224,9 @@ size_add_overflow(size_t x, size_t y)
     bool p;
 #if 0
 
+#elif defined(ckd_add)
+    p = ckd_add(&z, x, y);
+
 #elif __has_builtin(__builtin_add_overflow)
     p = __builtin_add_overflow(x, y, &z);