Copy va_lists by using va_copy, not by just assigning them.

configure

@@ -8586,6 +8586,119 @@ _ACEOF
 
 fi
 
+echo "$as_me:$LINENO: checking for va_copy" >&5
+echo $ECHO_N "checking for va_copy... $ECHO_C" >&6
+if test "${ac_cv_c_va_copy+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  cat >conftest.$ac_ext <<_ACEOF
+#line $LINENO "configure"
+#include "confdefs.h"
+#include <stdarg.h>
+#ifdef F77_DUMMY_MAIN
+#  ifdef __cplusplus
+     extern "C"
+#  endif
+   int F77_DUMMY_MAIN() { return 1; }
+#endif
+int
+main ()
+{
+va_list ap1, ap2;
+    va_copy(ap1,ap2);
+
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+         { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_c_va_copy="yes"
+else
+  echo "$as_me: failed program was:" >&5
+cat conftest.$ac_ext >&5
+ac_cv_c_va_copy="no"
+fi
+rm -f conftest.$ac_objext conftest$ac_exeext conftest.$ac_ext
+
+fi
+echo "$as_me:$LINENO: result: $ac_cv_c_va_copy" >&5
+echo "${ECHO_T}$ac_cv_c_va_copy" >&6
+if test "$ac_cv_c_va_copy" = "yes"
+then
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_VA_COPY 1
+_ACEOF
+
+fi
+echo "$as_me:$LINENO: checking for __va_copy" >&5
+echo $ECHO_N "checking for __va_copy... $ECHO_C" >&6
+if test "${ac_cv_c___va_copy+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  cat >conftest.$ac_ext <<_ACEOF
+#line $LINENO "configure"
+#include "confdefs.h"
+#include <stdarg.h>
+#ifdef F77_DUMMY_MAIN
+#  ifdef __cplusplus
+     extern "C"
+#  endif
+   int F77_DUMMY_MAIN() { return 1; }
+#endif
+int
+main ()
+{
+va_list ap1, ap2;
+    __va_copy(ap1,ap2);
+
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
+  (eval $ac_link) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+         { ac_try='test -s conftest$ac_exeext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  ac_cv_c___va_copy="yes"
+else
+  echo "$as_me: failed program was:" >&5
+cat conftest.$ac_ext >&5
+ac_cv_c___va_copy="no"
+fi
+rm -f conftest.$ac_objext conftest$ac_exeext conftest.$ac_ext
+
+fi
+echo "$as_me:$LINENO: result: $ac_cv_c___va_copy" >&5
+echo "${ECHO_T}$ac_cv_c___va_copy" >&6
+if test "$ac_cv_c___va_copy" = "yes"
+then
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE___VA_COPY 1
+_ACEOF
+
+fi
+
 echo "$as_me:$LINENO: checking for GNU style IPX support" >&5
 echo $ECHO_N "checking for GNU style IPX support... $ECHO_C" >&6
 if test "${ac_cv_c_ipx_gnu+set}" = set; then

configure.ac

@@ -447,6 +447,34 @@ then
     AC_DEFINE(HAVE_PPDEV, 1, [Define if we can use ppdev.h for parallel port access])
 fi
 
+dnl **** Check for va_copy ****
+AC_CACHE_CHECK([for va_copy], ac_cv_c_va_copy,
+ AC_TRY_LINK(
+   [#include <stdarg.h>],
+   [va_list ap1, ap2;
+    va_copy(ap1,ap2);
+   ],
+   [ac_cv_c_va_copy="yes"],
+   [ac_cv_c_va_copy="no"])
+ )
+if test "$ac_cv_c_va_copy" = "yes"
+then
+    AC_DEFINE(HAVE_VA_COPY, 1, [Define if we have va_copy])
+fi
+AC_CACHE_CHECK([for __va_copy], ac_cv_c___va_copy,
+ AC_TRY_LINK(
+   [#include <stdarg.h>],
+   [va_list ap1, ap2;
+    __va_copy(ap1,ap2);
+   ],
+   [ac_cv_c___va_copy="yes"],
+   [ac_cv_c___va_copy="no"])
+ )
+if test "$ac_cv_c___va_copy" = "yes"
+then
+    AC_DEFINE(HAVE___VA_COPY, 1, [Define if we have __va_copy])
+fi
+
 dnl **** Check for IPX (currently Linux only) ****
 AC_CACHE_CHECK([for GNU style IPX support], ac_cv_c_ipx_gnu,
  AC_TRY_COMPILE(

dlls/msvcrt/process.c

@@ -25,6 +25,10 @@
  *  open file handles, sometimes not. The docs are confusing
  * -No check for maximum path/argument/environment size is done
  */
+#include "config.h"
+
+#include <stdarg.h>
+
 #include "msvcrt.h"
 #include "ms_errno.h"
 
@@ -141,12 +145,22 @@ static char* msvcrt_argvtos(const char* const* arg, char delim)
  */
 static char* msvcrt_valisttos(const char* arg0, va_list alist, char delim)
 {
-  va_list alist2 = alist;
+  va_list alist2;
   long size;
   const char *arg;
   char* p;
   char *ret;
 
+#if HAVE_VA_COPY
+  va_copy(alist2,alist);
+#else
+# if HAVE___VA_COPY
+  __va_copy(alist2,alist);
+# else
+  alist2 = alist;
+# endif
+#endif
+
   if (!arg0 && !delim)
   {
       /* Return NULL for an empty environment list */

include/config.h.in

@@ -575,6 +575,9 @@
 /* Define to 1 if you have the `usleep' function. */
 #undef HAVE_USLEEP
 
+/* Define if we have va_copy */
+#undef HAVE_VA_COPY
+
 /* Define to 1 if you have the `vfscanf' function. */
 #undef HAVE_VFSCANF
 
@@ -638,6 +641,9 @@
 /* Define to 1 if you have the `__libc_fork' function. */
 #undef HAVE___LIBC_FORK
 
+/* Define if we have __va_copy */
+#undef HAVE___VA_COPY
+
 /* Define if stdcall symbols need to be decorated */
 #undef NEED_STDCALL_DECORATION