Description:
------------
./php-727 -r '$foo = "1HnyFwSJDjWFexD7oRr4HGTFwD8N6NsrfX"; $pattern = "[((?:(?(?<!):a?)+a?)+|\1)\8\C]u"; preg_match($pattern, $foo, $matches, PREG_OFFSET_CAPTURE, 3); print_r($matches);'

Increasing ulimit -s from the default of 8192 to 156275 seems to make this go away on a consistent basis. 

Expected result:
----------------
No crash.

Actual result:
--------------
==28465==ERROR: AddressSanitizer: stack-overflow on address 0x7ffc87ca4ff8 (pc 0x0000006032f1 bp 0x7ffc87ca53c0 sp 0x7ffc87ca4fe0 T0)
    #0 0x6032f0 in match /root/php-7.2.7/ext/pcre/pcrelib/pcre_exec.c:516
    #1 0x60630b in match /root/php-7.2.7/ext/pcre/pcrelib/pcre_exec.c:1612:7
    #2 0x60a657 in match /root/php-7.2.7/ext/pcre/pcrelib/pcre_exec.c:1388:7
    #3 0x62c3d0 in match /root/php-7.2.7/ext/pcre/pcrelib/pcre_exec.c:2061:7
    #4 0x62c3d0 in match /root/php-7.2.7/ext/pcre/pcrelib/pcre_exec.c:2061:7
    **SNIP**
    #244 0x62c3d0 in match /root/php-7.2.7/ext/pcre/pcrelib/pcre_exec.c:2061:7
    #245 0x62c3d0 in match /root/php-7.2.7/ext/pcre/pcrelib/pcre_exec.c:2061:7
    #246 0x62c3d0 in match /root/php-7.2.7/ext/pcre/pcrelib/pcre_exec.c:2061:7
    #247 0x62c3d0 in match /root/php-7.2.7/ext/pcre/pcrelib/pcre_exec.c:2061:7
    #248 0x62c3d0 in match /root/php-7.2.7/ext/pcre/pcrelib/pcre_exec.c:2061:7

SUMMARY: AddressSanitizer: stack-overflow /root/php-7.2.7/ext/pcre/pcrelib/pcre_exec.c:516 in match
==28465==ABORTING