1 files changed, 37 insertions, 12 deletions
diff --git a/manual/examples/mbstouwcs.c b/manual/examples/mbstouwcs.c
index 5d223da2ae..c94e1fa790 100644
--- a/manual/examples/mbstouwcs.c
+++ b/manual/examples/mbstouwcs.c
@@ -1,3 +1,4 @@
+#include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
 #include <wchar.h>
@@ -7,22 +8,46 @@
 wchar_t *
 mbstouwcs (const char *s)
 {
-  size_t len = strlen (s);
-  wchar_t *result = malloc ((len + 1) * sizeof (wchar_t));
+  /* Include the null terminator in the conversion.  */
+  size_t len = strlen (s) + 1;
+  wchar_t *result = reallocarray (NULL, len, sizeof (wchar_t));
+  if (result == NULL)
+    return NULL;
+
   wchar_t *wcp = result;
-  wchar_t tmp[1];
   mbstate_t state;
-  size_t nbytes;
-
   memset (&state, '\0', sizeof (state));
-  while ((nbytes = mbrtowc (tmp, s, len, &state)) > 0)
+
+  while (true)
     {
-      if (nbytes >= (size_t) -2)
-        /* Invalid input string.  */
-        return NULL;
-      *wcp++ = towupper (tmp[0]);
-      len -= nbytes;
-      s += nbytes;
+      wchar_t wc;
+      size_t nbytes = mbrtowc (&wc, s, len, &state);
+      if (nbytes == 0)
+        {
+          /* Terminate the result string.  */
+          *wcp = L'\0';
+          break;
+        }
+      else if (nbytes == (size_t) -2)
+        {
+          /* Truncated input string.  */
+          errno = EILSEQ;
+          free (result);
+          return NULL;
+        }
+      else if (nbytes == (size_t) -1)
+        {
+          /* Some other error (including EILSEQ).  */
+          free (result);
+          return NULL;
+        }
+      else
+        {
+          /* A character was converted.  */
+          *wcp++ = towupper (wc);
+          len -= nbytes;
+          s += nbytes;
+        }
     }
   return result;
 }