libroot: add reallocarray() from POSIX.1-2024

Change-Id: I75d469ad9a01eb221ca607830589a7794eff71e8
Reviewed-on: https://review.haiku-os.org/c/haiku/+/8512
Reviewed-by: waddlesplash <[email protected]>
Tested-by: Commit checker robot <[email protected]>

headers/posix/stdlib.h

@@ -51,6 +51,7 @@ extern void		*malloc(size_t size);
 extern int		posix_memalign(void **_pointer, size_t alignment, size_t size);
 extern void 	*aligned_alloc(size_t alignment, size_t size) _ALIGNED_BY_ARG(1);
 extern void		*realloc(void *oldPointer, size_t newSize);
+extern void		*reallocarray(void *ptr, size_t nelem, size_t elsize);
 
 /* process termination */
 extern void		abort(void) __attribute__((noreturn));

src/system/libroot/posix/stdlib/Jamfile

@@ -28,6 +28,7 @@ for architectureObject in [ MultiArchSubDirSetup ] {
 			qsort.c
 			radixsort.c
 			random.c
+			reallocarray.cpp
 			realpath.cpp
 			strfmon.c
 			strtol.c

src/system/libroot/posix/stdlib/reallocarray.cpp

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2024, Jérôme Duval, [email protected]
+ * Distributed under the terms of the MIT License.
+ */
+
+
+#include <stdlib.h>
+
+#include <errno.h>
+#include <stdint.h>
+
+
+extern "C" void*
+reallocarray(void* ptr, size_t nelem, size_t elsize)
+{
+	if (elsize != 0 && nelem != 0 && nelem > SIZE_MAX / elsize) {
+		errno = ENOMEM;
+		return NULL;
+	}
+	return realloc(ptr, nelem * elsize);
+}