path: root/src/malloc/memalign.c
diff options
authorRich Felker <>2018-04-17 18:36:19 -0400
committerRich Felker <>2018-04-18 14:22:49 -0400
commitc9f415d7ea2dace5bf77f6518b6afc36bb7a5732 (patch)
tree53e90cc28b51fd50185527bfbd71411e1ef05843 /src/malloc/memalign.c
parentc1014a812c90bab3c9c989863e4ebb129e987de6 (diff)
allow interposition/replacement of allocator (malloc)
replacement is subject to conditions on the replacement functions. they may only call functions which are async-signal-safe, as specified either by POSIX or as an implementation-defined extension. if any allocator functions are replaced, at least malloc, realloc, and free must be provided. if calloc is not provided, it will behave as malloc+memset. any of the memalign-family functions not provided will fail with ENOMEM. in order to implement the above properties, calloc and __memalign check that they are using their own malloc or free, respectively. choice to check malloc or free is based on considerations of supporting __simple_malloc. in order to make this work, calloc is split into separate versions for __simple_malloc and full malloc; commit ba819787ee93ceae94efd274f7849e317c1bff58 already did most of the split anyway, and completing it saves an extra call frame. previously, use of -Bsymbolic-functions made dynamic interposition impossible. now, we are using an explicit dynamic-list, so add allocator functions to the list. most are not referenced anyway, but all are added for completeness.
Diffstat (limited to 'src/malloc/memalign.c')
1 files changed, 2 insertions, 4 deletions
diff --git a/src/malloc/memalign.c b/src/malloc/memalign.c
index 006bd21c..35b67599 100644
--- a/src/malloc/memalign.c
+++ b/src/malloc/memalign.c
@@ -3,9 +3,7 @@
#include <errno.h>
#include "libc.h"
-/* This function should work with most dlmalloc-like chunk bookkeeping
- * systems, but it's only guaranteed to work with the native implementation
- * used in this library. */
+void __internal_free(void *);
void *__memalign(size_t align, size_t len)
@@ -17,7 +15,7 @@ void *__memalign(size_t align, size_t len)
return NULL;
- if (len > SIZE_MAX - align) {
+ if (len > SIZE_MAX - align || free != __internal_free) {
errno = ENOMEM;
return NULL;