[PATCH 1/4] libc/stdlib: Use __builtin_mul_overflow for reallocarray and calloc
Keith Packard
keithp@keithp.com
Tue Aug 11 23:05:40 GMT 2020
This built-in function (available in both gcc and clang) is more
efficient and generates shorter code than open-coding the test.
Signed-off-by: Keith Packard <keithp@keithp.com>
---
newlib/libc/stdlib/mallocr.c | 8 +++++++-
newlib/libc/stdlib/nano-mallocr.c | 12 ++++++++++--
newlib/libc/stdlib/reallocarray.c | 17 +++++------------
3 files changed, 22 insertions(+), 15 deletions(-)
diff --git a/newlib/libc/stdlib/mallocr.c b/newlib/libc/stdlib/mallocr.c
index 26d1c89cc..9ad720ada 100644
--- a/newlib/libc/stdlib/mallocr.c
+++ b/newlib/libc/stdlib/mallocr.c
@@ -3194,7 +3194,7 @@ Void_t* cALLOc(RARG n, elem_size) RDECL size_t n; size_t elem_size;
mchunkptr p;
INTERNAL_SIZE_T csz;
- INTERNAL_SIZE_T sz = n * elem_size;
+ INTERNAL_SIZE_T sz;
#if MORECORE_CLEARS
mchunkptr oldtop;
@@ -3202,6 +3202,12 @@ Void_t* cALLOc(RARG n, elem_size) RDECL size_t n; size_t elem_size;
#endif
Void_t* mem;
+ if (__builtin_mul_overflow((INTERNAL_SIZE_T) n, (INTERNAL_SIZE_T) elem_size, &sz))
+ {
+ errno = ENOMEM;
+ return 0;
+ }
+
/* check if expand_top called, in which case don't need to clear */
#if MORECORE_CLEARS
MALLOC_LOCK;
diff --git a/newlib/libc/stdlib/nano-mallocr.c b/newlib/libc/stdlib/nano-mallocr.c
index 13b72c99f..04465eb9e 100644
--- a/newlib/libc/stdlib/nano-mallocr.c
+++ b/newlib/libc/stdlib/nano-mallocr.c
@@ -445,8 +445,16 @@ void nano_cfree(RARG void * ptr)
* Implement calloc simply by calling malloc and set zero */
void * nano_calloc(RARG malloc_size_t n, malloc_size_t elem)
{
- void * mem = nano_malloc(RCALL n * elem);
- if (mem != NULL) memset(mem, 0, n * elem);
+ ptrdiff_t bytes;
+ void * mem;
+
+ if (__builtin_mul_overflow (n, elem, &bytes))
+ {
+ RERRNO = ENOMEM;
+ return NULL;
+ }
+ mem = nano_malloc(bytes);
+ if (mem != NULL) memset(mem, 0, bytes);
return mem;
}
#endif /* DEFINE_CALLOC */
diff --git a/newlib/libc/stdlib/reallocarray.c b/newlib/libc/stdlib/reallocarray.c
index 4b6cccb70..d1f63c66b 100644
--- a/newlib/libc/stdlib/reallocarray.c
+++ b/newlib/libc/stdlib/reallocarray.c
@@ -16,27 +16,20 @@
*/
#include <sys/cdefs.h>
-__FBSDID("$FreeBSD: head/lib/libc/stdlib/reallocarray.c 282314 2015-05-01 18:32:16Z bapt $");
-
#include <sys/types.h>
#include <errno.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)
{
+ ptrdiff_t bytes;
- if ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
- nmemb > 0 && SIZE_MAX / nmemb < size) {
+ if (__builtin_mul_overflow (nmemb, size, &bytes))
+ {
errno = ENOMEM;
- return (NULL);
+ return NULL;
}
- return (realloc(optr, size * nmemb));
+ return realloc(optr, bytes);
}
--
2.28.0
More information about the Newlib
mailing list