Description:
------------
If the command ran by exec outputs a line that is 2*EXEC_INPUT_BUF longer than the previous line a segfault may occur.  It is not difficult to see why this happens just by reading the source code.

In exec.c, line 118, reads

if (buflen < (bufl + EXEC_INPUT_BUF)) {

This condition is correct only the first time, e.g when b=buf.  I think the like should be

if (buflen < (bufl + (b - buf) + EXEC_INPUT_BUF)) {


Reproduce code:
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#!/usr/local/bin/php
<?php
$out = array();
$status = -1;
exec('/usr/bin/seq 5000 | tr \'\n\' \' \'', $out, $status);
print_r($out);
?>

Expected result:
----------------
Numbers from 1 to 5000 separated by blanks on one line.

Actual result:
--------------
segfault