+/* Checked size_t computations. */
+#include "xsize.h"
+
+static inline char *
+xstrcat (size_t argcount, va_list args)
+{
+ char *result;
+ va_list ap;
+ size_t totalsize;
+ size_t i;
+ char *p;
+
+ /* Determine the total size. */
+ totalsize = 0;
+ va_copy (ap, args);
+ for (i = argcount; i > 0; i--)
+ {
+ const char *next = va_arg (ap, const char *);
+ totalsize = xsum (totalsize, strlen (next));
+ }
+ va_end (ap);
+
+ /* Test for overflow in the summing pass above or in (totalsize + 1) below.
+ Also, don't return a string longer than INT_MAX, for consistency with
+ vasprintf(). */
+ if (totalsize == SIZE_MAX || totalsize > INT_MAX)
+ {
+ errno = EOVERFLOW;
+ return NULL;
+ }
+
+ /* Allocate and fill the result string. */
+ result = XNMALLOC (totalsize + 1, char);
+ p = result;
+ for (i = argcount; i > 0; i--)
+ {
+ const char *next = va_arg (args, const char *);
+ size_t len = strlen (next);
+ memcpy (p, next, len);
+ p += len;
+ }
+ *p = '\0';
+
+ return result;
+}
+