add reallocarray from musl

include/stdlib.h

@@ -985,6 +985,8 @@ extern int getpt (void);
    three, but may be less than NELEM), or -1 if an error occurred.  */
 extern int getloadavg (double __loadavg[], int __nelem)
      __THROW __nonnull ((1));
+
+extern void *reallocarray (void *__ptr, size_t __m, size_t __n);
 #endif
 
 #ifdef _LIBC

libc/stdlib/malloc-standard/reallocarray.c

@@ -0,0 +1,36 @@
+/*
+Copyright © 2005-2020 Rich Felker, et al.
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+#define _BSD_SOURCE
+#include <errno.h>
+#include <stdlib.h>
+
+void *reallocarray(void *ptr, size_t m, size_t n)
+{
+	if (n && m > -1 / n) {
+		errno = ENOMEM;
+		return 0;
+	}
+
+	return realloc(ptr, m * n);
+}