lib{c,openbsd}: use ckd_mul() for overflow checking in re(c)allocarray

Summary:
This makes the code easier to understand and slightly faster,
but requires C23.  calloc() would  benefit, too, but I didn't
want to touch the imported jemalloc code base.

Reviewed by:	kib
Differential Revision:	https://reviews.freebsd.org/D52854

1 files changed, 5 insertions, 9 deletions

diff --git a/lib/libc/stdlib/reallocarray.c b/lib/libc/stdlib/reallocarray.c
index 0868804486cc..3632734c84de 100644
--- a/lib/libc/stdlib/reallocarray.c
+++ b/lib/libc/stdlib/reallocarray.c
@@ -17,23 +17,19 @@
 
 #include <sys/types.h>
 #include <errno.h>
+#include <stdckdint.h>
 #include <stdint.h>
 #include <stdlib.h>
 
-/*
- * This is sqrt(SIZE_MAX+1), as s1*s2 <= SIZE_MAX
- * if both s1 < MUL_NO_OVERFLOW and s2 < MUL_NO_OVERFLOW
- */
-#define MUL_NO_OVERFLOW	((size_t)1 << (sizeof(size_t) * 4))
-
 void *
 reallocarray(void *optr, size_t nmemb, size_t size)
 {
+	size_t nbytes;
 
-	if ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
-	    nmemb > 0 && SIZE_MAX / nmemb < size) {
+	if (ckd_mul(&nbytes, nmemb, size)) {
 		errno = ENOMEM;
 		return (NULL);
 	}
-	return (realloc(optr, size * nmemb));
+
+	return (realloc(optr, nbytes));
 }