Updated all cygwin packages to current versions, installed httpd
2.4.16-1.  On startup httpd segfaults:

Exception: STATUS_ACCESS_VIOLATION at eip=65DC5D78
eax=8004E028 ebx=00000001 ecx=00000000 edx=8004DFF0 esi=80014490
edi=80016498
ebp=0028CC78 esp=0028CB5C program=C:\cygwin\usr\sbin\httpd.exe, pid
25500, thread main
cs=0023 ds=002B es=002B fs=0053 gs=002B ss=002B
Stack trace:
Frame     Function  Args
0028CC78  65DC5D78 (00000003, 0028CC9C, 80010100, 00000020)
0028CD28  6100846A (00000000, 0028CD84, 610074F0, 00000000)
End of stack trace

The log contains the following:

[Sun Jul 26 16:59:15.693980 2015] [core:emerg] [pid 19552] (88)Function
not implemented: AH00023: Couldn't create the proxy mutex
[Sun Jul 26 16:59:15.693980 2015] [proxy:crit] [pid 19552] (88)Function
not implemented: AH02478: failed to create proxy mutex
AH00016: Configuration Failed

Google turned up one other question citing the same symptoms, but on a
Chinese website, no answers so far.

cygcheck.out attached

Suggestions on how to troubleshoot?  I can provide an strace output
(67k lines, 460kB gzipped) if desired.

-- 
Jim Garrison (jhg@acm.org)
PGP Keys at http://www.jhmg.net RSA 0x04B73B7F DH 0x70738D88