Description:
------------
A segmentation fault can occur in zend_error() with --enable-dtrace.
The zend_vspprintf() call in the DTRACE_ERROR_ENABLED() block leaves
args undefined:

  "If ap is passed to a function that uses va_arg(ap,type) then the
  value of ap is undefined after the return of that function."

When args is used again later in zend_error(), a seg fault can occur.

Test script:
---------------
As root:
-------------------
# dtrace -Z -s error.d 
dtrace: script 'error.d' matched 0 probes
CPU     ID                    FUNCTION:NAME
  0      6                 zend_error:error PHP error
--------------------


As a normal user:
--------------------
$ php error.php 
Segmentation fault (core dumped)
--------------------

Where error.d is:

php*:::error { printf("PHP error\n"); }

and error.php is:

<?php trigger_error('This is an error', E_USER_ERROR); ?>