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oldmalloc: preserve errno across free

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as an outcome of Austin Group issue #385, future versions of the
standard will require free not to alter the value of errno. save and
restore it individually around the calls to madvise and munmap so that
the cost is not imposed on calls to free that do not result in any
syscall.
This commit is contained in:
Rich Felker 2021-01-30 17:28:08 -05:00
parent 98b9df994c
commit 9b77aaca86
1 changed files with 4 additions and 0 deletions
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4
src/malloc/oldmalloc/malloc.c
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@ -481,12 +481,14 @@ void __bin_chunk(struct chunk *self)
if (size > RECLAIM && (size^(size-osize)) > size-osize) {
uintptr_t a = (uintptr_t)self + SIZE_ALIGN+PAGE_SIZE-1 & -PAGE_SIZE;
uintptr_t b = (uintptr_t)next - SIZE_ALIGN & -PAGE_SIZE;
int e = errno;
#if 1
__madvise((void *)a, b-a, MADV_DONTNEED);
#else
__mmap((void *)a, b-a, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED, -1, 0);
#endif
errno = e;
}
unlock_bin(i);
@ -499,7 +501,9 @@ static void unmap_chunk(struct chunk *self)
size_t len = CHUNK_SIZE(self) + extra;
/* Crash on double free */
if (extra & 1) a_crash();
int e = errno;
__munmap(base, len);
errno = e;
}
void free(void *p)