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authorRich Felker <dalias@aerifal.cx>2021-01-30 17:14:20 -0500
committerRich Felker <dalias@aerifal.cx>2021-01-30 17:14:20 -0500
commit2010df0d64570db4ce29cc7df0e31f81aa26ae4a (patch)
tree6eeebcbc7f665b45936d10b2d62e0c19e6765567 /src
parent9afed99c224ab33578623744f40d31bee84ec6ba (diff)
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preserve errno across free
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.
Diffstat (limited to 'src')
-rw-r--r--src/malloc/mallocng/free.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/src/malloc/mallocng/free.c b/src/malloc/mallocng/free.c
index 40745f97..418a085c 100644
--- a/src/malloc/mallocng/free.c
+++ b/src/malloc/mallocng/free.c
@@ -119,7 +119,11 @@ void free(void *p)
 	if (((uintptr_t)(start-1) ^ (uintptr_t)end) >= 2*PGSZ && g->last_idx) {
 		unsigned char *base = start + (-(uintptr_t)start & (PGSZ-1));
 		size_t len = (end-base) & -PGSZ;
-		if (len) madvise(base, len, MADV_FREE);
+		if (len) {
+			int e = errno;
+			madvise(base, len, MADV_FREE);
+			errno = e;
+		}
 	}
 
 	// atomic free without locking if this is neither first or last slot
@@ -139,5 +143,9 @@ void free(void *p)
 	wrlock();
 	struct mapinfo mi = nontrivial_free(g, idx);
 	unlock();
-	if (mi.len) munmap(mi.base, mi.len);
+	if (mi.len) {
+		int e = errno;
+		munmap(mi.base, mi.len);
+		errno = e;
+	}
 }