Use safer allocation macros

Use of these macros, apart from the benefits mentioned in the commit
that adds the macros, has some other good side effects:

-  Consistency in getting the size of the object from sizeof(type),
   instead of a mix of sizeof(type) sometimes and sizeof(*p) other
   times.

-  More readable code: no casts, and no sizeof(), so also shorter lines
   that we don't need to cut.

-  Consistency in using array allocation calls for allocations of arrays
   of objects, even when the object size is 1.

Cc: Valentin V. Bartenev <vbartenev@gmail.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

src/vipw.c

@@ -26,6 +26,8 @@
 #include <sys/types.h>
 #include <unistd.h>
 #include <utime.h>
+
+#include "alloc.h"
 #include "defines.h"
 #include "groupio.h"
 #include "nscd.h"
@@ -302,7 +304,7 @@ vipwedit (const char *file, int (*file_lock) (void), int (*file_unlock) (void))
 				continue;
 		}
 
-		buf = (char *) malloc (strlen (editor) + strlen (fileedit) + 2);
+		buf = MALLOCARRAY(strlen(editor) + strlen(fileedit) + 2, char);
 		snprintf (buf, strlen (editor) + strlen (fileedit) + 2,
 		          "%s %s", editor, fileedit);
 		status = system (buf);
@@ -418,7 +420,7 @@ vipwedit (const char *file, int (*file_lock) (void), int (*file_unlock) (void))
 		if (stat (file, &st1) != 0) {
 			vipwexit (_("failed to stat edited file"), errno, 1);
 		}
-		to_rename = malloc (strlen (file) + 2);
+		to_rename = MALLOCARRAY (strlen (file) + 2, char);
 		if (NULL == to_rename) {
 			vipwexit (_("failed to allocate memory"), errno, 1);
 		}