Bugfix.

* libmailutils/string/vasnprintf.c (mu_vasnprintf): Operate on
a fresh copy of va_alist in each new iteration.
* libproto/imap/folder.c: Likewise.
* libproto/nntp/nntp_sendline.c: Likewise.

@@ -46,7 +46,13 @@ mu_vasnprintf (char **pbuf, size_t *psize, const char *fmt, va_list ap)
   
   for (;;)
     {
-      ssize_t n = vsnprintf (buf, buflen, fmt, ap);
+      ssize_t n;
+      va_list aq;
+
+      va_copy(aq, ap);
+      n = vsnprintf (buf, buflen, fmt, aq);
+      va_end(aq);
+
       if (n < 0 || n >= buflen || !memchr (buf, '\0', n + 1))
 	{
 	  char *newbuf;

@@ -2150,7 +2150,10 @@ imap_writeline (f_imap_t f_imap, const char *format, ...)
   va_start(ap, format);
   do
     {
-      len = vsnprintf (f_imap->buffer, f_imap->buflen, format, ap);
+      va_list aq;
+      va_copy(aq, ap);
+      len = vsnprintf (f_imap->buffer, f_imap->buflen, format, aq);
+      va_end(aq);
       if (len < 0 || len >= (int)f_imap->buflen
           || !memchr (f_imap->buffer, '\0', len + 1))
         {

@@ -88,7 +88,10 @@ mu_nntp_writeline (mu_nntp_t nntp, const char *format, ...)
      let's try to cope.  */
   do
     {
-      len = vsnprintf (nntp->io.buf, nntp->io.len - 1, format, ap);
+      va_list aq;
+      va_copy(aq, ap);
+      len = vsnprintf (nntp->io.buf, nntp->io.len - 1, format, aq);
+      va_end(aq);
       if (len < 0 || len >= (int)nntp->io.len
 	  || !memchr (nntp->io.buf, '\0', len + 1))
 	{