[musl] [PATCH] implement reallocarray(3)

[Ariadne Conill <ariadne@dereferenced.org>]

reallocarray(3) is an extension introduced by OpenBSD, which
introduces calloc(3) overflow checking to realloc(3).

glibc 2.28 introduced support for this function behind _GNU_SOURCE,
while glibc 2.29 allows its usage in _DEFAULT_SOURCE, so I made it
available by default as well.
---
 include/stdlib.h          |  1 +
 src/malloc/reallocarray.c | 13 +++++++++++++
 2 files changed, 14 insertions(+)
 create mode 100644 src/malloc/reallocarray.c

diff --git a/include/stdlib.h b/include/stdlib.h
index 194c2033..8db8e5cc 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -38,6 +38,7 @@ void srand (unsigned);
 void *malloc (size_t);
 void *calloc (size_t, size_t);
 void *realloc (void *, size_t);
+void *reallocarray (void *, size_t, size_t);
 void free (void *);
 void *aligned_alloc(size_t, size_t);
 
diff --git a/src/malloc/reallocarray.c b/src/malloc/reallocarray.c
new file mode 100644
index 00000000..733cb16a
--- /dev/null
+++ b/src/malloc/reallocarray.c
@@ -0,0 +1,13 @@
+#include <errno.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+void *reallocarray(void *ptr, size_t m, size_t n)
+{
+	if (n && m > (size_t) -1 / n) {
+		errno = ENOMEM;
+		return NULL;
+	}
+
+	return realloc(ptr, m * n);
+}
-- 
2.27.0