[musl] [PATCH v2] implement recallocarray(3)

[Ariadne Conill <ariadne@dereferenced.org>]

This OpenBSD extension is similar to reallocarray(3), but
zero-initializes the new memory area.

This extension is placed in _BSD_SOURCE, like
reallocarray(3).

This patch depends on reallocarray(3) already being
present, and will not compile without it.
---
 include/stdlib.h           |  1 +
 src/malloc/recallocarray.c | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)
 create mode 100644 src/malloc/recallocarray.c

diff --git a/include/stdlib.h b/include/stdlib.h
index b54a051f..a0412ad4 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -146,6 +146,7 @@ int clearenv(void);
 #define WCOREDUMP(s) ((s) & 0x80)
 #define WIFCONTINUED(s) ((s) == 0xffff)
 void *reallocarray (void *, size_t, size_t);
+void *recallocarray (void *, size_t, size_t, size_t);
 #endif
 
 #ifdef _GNU_SOURCE
diff --git a/src/malloc/recallocarray.c b/src/malloc/recallocarray.c
new file mode 100644
index 00000000..a7333c47
--- /dev/null
+++ b/src/malloc/recallocarray.c
@@ -0,0 +1,33 @@
+#define _BSD_SOURCE
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+void *recallocarray(void *ptr, size_t om, size_t m, size_t n)
+{
+	void *newptr;
+	size_t old_size, new_size;
+
+	if (n && m > -1 / n) {
+		errno = ENOMEM;
+		return 0;
+	}
+	new_size = m * n;
+
+	if (n && om > -1 / n) {
+		errno = EINVAL;
+		return 0;
+	}
+	old_size = om * n;
+
+	if (new_size <= old_size) {
+		memset((char *) ptr + new_size, 0, old_size - new_size);
+	}
+
+	newptr = realloc(ptr, m * n);
+	if (new_size > old_size) {
+		memset((char *) ptr + old_size, 0, new_size - old_size);
+	}
+
+	return newptr;
+}
-- 
2.28.0