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diff --git a/gnu/xvasprintf.c b/gnu/xvasprintf.c
new file mode 100644
index 0000000..448de07
--- /dev/null
+++ b/gnu/xvasprintf.c
@@ -0,0 +1,112 @@
+/* -*- buffer-read-only: t -*- vi: set ro: */
+/* DO NOT EDIT! GENERATED AUTOMATICALLY! */
+/* vasprintf and asprintf with out-of-memory checking.
+   Copyright (C) 1999, 2002-2004, 2006-2010 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include "xvasprintf.h"
+
+#include <errno.h>
+#include <limits.h>
+#include <string.h>
+#include <stdio.h>
+
+#include "xalloc.h"
+
+/* 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;
+}
+
+char *
+xvasprintf (const char *format, va_list args)
+{
+  char *result;
+
+  /* Recognize the special case format = "%s...%s".  It is a frequently used
+     idiom for string concatenation and needs to be fast.  We don't want to
+     have a separate function xstrcat() for this purpose.  */
+  {
+    size_t argcount = 0;
+    const char *f;
+
+    for (f = format;;)
+      {
+        if (*f == '\0')
+          /* Recognized the special case of string concatenation.  */
+          return xstrcat (argcount, args);
+        if (*f != '%')
+          break;
+        f++;
+        if (*f != 's')
+          break;
+        f++;
+        argcount++;
+      }
+  }
+
+  if (vasprintf (&result, format, args) < 0)
+    {
+      if (errno == ENOMEM)
+        xalloc_die ();
+      return NULL;
+    }
+
+  return result;
+}