If zPathInfo is NULL. Fossil crashes in process_one_web_page. This can be demonstrated by using a CGI script with directory: where no further path is specified.
<verbatim>
$ gdb --args ./fossil.exe cgi
GNU gdb 6.8
Copyright (C) 2008 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i686-pc-mingw32"...
(gdb) r
Starting program: cgi c:/Apache2.

[New thread 2100.0xce0]
Program received signal SIGSEGV, Segmentation fault.
process_one_web_page (zNotFound=<value optimized out>) at wbld/main_.c:897
897         while( zPathInfo[i] && zPathInfo[i]!='/' ){ i++; }
(gdb) q
The program is running.  Exit anyway? (y or n) y
</verbatim>