Introducing recallocarray(3), a blend of calloc(3) and reallocarray(3)

with the added feature that released memory is cleared. Much input from various
developers. ok deraadt@ tom@

1 files changed, 81 insertions, 0 deletions

diff --git a/src/lib/libc/stdlib/recallocarray.c b/src/lib/libc/stdlib/recallocarray.c
new file mode 100644
index 0000000000..a2f37fe81a
--- /dev/null
+++ b/src/lib/libc/stdlib/recallocarray.c
@@ -0,0 +1,81 @@
+/*      $OpenBSD: recallocarray.c,v 1.1 2017/03/06 18:44:21 otto Exp $  */
+/*
+ * Copyright (c) 2008, 2017 Otto Moerbeek <otto@drijf.net>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <errno.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <unistd.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 *
+recallocarray(void *ptr, size_t oldnmemb, size_t newnmemb, size_t size)
+{
+        size_t oldsize, newsize;
+        void *newptr;
+
+        if (ptr == NULL)
+                return calloc(newnmemb, size);
+
+        if ((newnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
+            newnmemb > 0 && SIZE_MAX / newnmemb < size) {
+                errno = ENOMEM;
+                return NULL;
+        }
+        newsize = newnmemb * size;
+
+        if ((oldnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
+            oldnmemb > 0 && SIZE_MAX / oldnmemb < size) {
+                errno = EINVAL;
+                return NULL;
+        }
+        oldsize = oldnmemb * size;
+        
+        /*
+         * Don't bother too much if we're shrinking just a bit,
+         * we do not shrink for series of small steps, oh well.
+         */
+        if (newsize <= oldsize) {
+                size_t d = oldsize - newsize;
+
+                if (d < oldsize / 2 && d < getpagesize()) {
+                        memset((char *)ptr + newsize, 0, d);
+                        return ptr;
+                }
+        }
+
+        newptr = malloc(newsize);
+        if (newptr == NULL)
+                return NULL;
+
+        if (newsize > oldsize) {
+                memcpy(newptr, ptr, oldsize);
+                memset((char *)newptr + oldsize, 0, newsize - oldsize);
+        } else
+                memcpy(newptr, ptr, newsize);
+
+        explicit_bzero(ptr, oldsize);
+        free(ptr);
+
+        return newptr;
+}
+DEF_WEAK(recallocarray);