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libc/stdlib: Use __builtin_mul_overflow for reallocarray and calloc 

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>
This commit is contained in:
Keith Packard via Newlib 2020-08-11 16:05:40 -07:00 committed by Corinna Vinschen
parent bafd65f2fb
commit 588a5e1dde
3 changed files with 22 additions and 15 deletions
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8
newlib/libc/stdlib/mallocr.c
View File

@ -3194,7 +3194,7 @@ Void_t* cALLOc(RARG n, elem_size) RDECL size_t n; size_t elem_size;
mchunkptr p; mchunkptr p;
INTERNAL_SIZE_T csz; INTERNAL_SIZE_T csz;
INTERNAL_SIZE_T sz = n * elem_size; INTERNAL_SIZE_T sz;
#if MORECORE_CLEARS #if MORECORE_CLEARS
mchunkptr oldtop; mchunkptr oldtop;
@ -3202,6 +3202,12 @@ Void_t* cALLOc(RARG n, elem_size) RDECL size_t n; size_t elem_size;
#endif #endif
Void_t* mem; 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 */ /* check if expand_top called, in which case don't need to clear */
#if MORECORE_CLEARS #if MORECORE_CLEARS
MALLOC_LOCK; MALLOC_LOCK;

12
newlib/libc/stdlib/nano-mallocr.c
View File

@ -445,8 +445,16 @@ void nano_cfree(RARG void * ptr)
* Implement calloc simply by calling malloc and set zero */ * Implement calloc simply by calling malloc and set zero */
void * nano_calloc(RARG malloc_size_t n, malloc_size_t elem) void * nano_calloc(RARG malloc_size_t n, malloc_size_t elem)
{ {
void * mem = nano_malloc(RCALL n * elem); ptrdiff_t bytes;
if (mem != NULL) memset(mem, 0, n * elem); 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; return mem;
} }
#endif /* DEFINE_CALLOC */ #endif /* DEFINE_CALLOC */

17
newlib/libc/stdlib/reallocarray.c
View File

@ -16,27 +16,20 @@
*/ */
#include <sys/cdefs.h> #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 <sys/types.h>
#include <errno.h> #include <errno.h>
#include <stdint.h> #include <stdint.h>
#include <stdlib.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 * void *
reallocarray(void *optr, size_t nmemb, size_t size) reallocarray(void *optr, size_t nmemb, size_t size)
{ {
ptrdiff_t bytes;
if ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) && if (__builtin_mul_overflow (nmemb, size, &bytes))
nmemb > 0 && SIZE_MAX / nmemb < size) { {
errno = ENOMEM; errno = ENOMEM;
return (NULL); return NULL;
} }
return (realloc(optr, size * nmemb)); return realloc(optr, bytes);
} }