Description of problem:
Starting up PHP-FPM fails with APCu (php-pecl-apcu) enabled.

Version-Release number of selected component (if applicable):
5.1.8-4.fc27

How reproducible:
Every time.

Steps to Reproduce:
1. Install: dnf install php-fpm and php-pecl-apcu
2. Start: systemctl start php-fpm

Actual results:
[straussd@t560 ~]$ sudo systemctl restart php-fpm
Job for php-fpm.service failed because a fatal signal was delivered causing the control process to dump core.
See "systemctl  status php-fpm.service" and "journalctl  -xe" for details.
[straussd@t560 ~]$ sudo systemctl  status php-fpm.service
● php-fpm.service - The PHP FastCGI Process Manager
   Loaded: loaded (/usr/lib/systemd/system/php-fpm.service; disabled; vendor preset: disabled)
   Active: failed (Result: core-dump) since Wed 2017-11-15 18:20:04 PST; 2s ago
  Process: 30609 ExecStart=/usr/sbin/php-fpm --nodaemonize (code=dumped, signal=SEGV)
 Main PID: 30609 (code=dumped, signal=SEGV)

Nov 15 18:20:04 t560.davidstrauss.net systemd[1]: Starting The PHP FastCGI Process Manager...
Nov 15 18:20:04 t560.davidstrauss.net php-fpm[30609]: [15-Nov-2017 18:20:04] NOTICE: PHP message: PHP Fatal error:  PHP Startup: apc_mmap: mmap failed: in Unknown on line 0
Nov 15 18:20:04 t560.davidstrauss.net systemd[1]: php-fpm.service: Main process exited, code=dumped, status=11/SEGV
Nov 15 18:20:04 t560.davidstrauss.net systemd[1]: Failed to start The PHP FastCGI Process Manager.
Nov 15 18:20:04 t560.davidstrauss.net systemd[1]: php-fpm.service: Unit entered failed state.
Nov 15 18:20:04 t560.davidstrauss.net systemd[1]: php-fpm.service: Failed with result 'core-dump'.


Expected results:
Successful PHP-FPM startup with APCu.

Additional info:
Removing or disabling APCu fixes the issue. Commenting out "apc.mmap_file_mask=/tmp/apc.XXXXXX" in /etc/php.d/40-apcu.ini switches APCu to using an anonymous mmap and also works around the issue.

Abrt seems unable to create a suitable backtrace (either on my machine or on the hosted Fedora backtrace servers):

--- Running report_uReport ---
('report_uReport' completed successfully)

--- Running analyze_CCpp ---
Ok to upload core dump? (It may contain sensitive data). If your answer is 'No', a stack trace will be generated locally. (It may download a huge amount of data). 'NO'
Analyzing coredump 'coredump'
All debuginfo files are available
Generating backtrace
Backtrace is generated and saved, 32881 bytes

--- Running analyze_BodhiUpdates ---
Looking for similar problems in bugzilla

A notice below says:

Reporting disabled because the backtrace is unusable.

coredumpctl has more success:

[straussd@t560 ~]$ coredumpctl info
           PID: 28165 (php-fpm)
           UID: 0 (root)
           GID: 0 (root)
        Signal: 11 (SEGV)
     Timestamp: Wed 2017-11-15 18:06:31 PST (23min ago)
  Command Line: /usr/sbin/php-fpm --nodaemonize
    Executable: /usr/sbin/php-fpm
 Control Group: /system.slice/php-fpm.service
          Unit: php-fpm.service
         Slice: system.slice
       Boot ID: 25eb6c2a86544ff8ada94f8964dd7685
    Machine ID: 090dfce8e91946609388331241a392a1
      Hostname: t560.davidstrauss.net
       Storage: /var/lib/systemd/coredump/core.php-fpm.0.25eb6c2a86544ff8ada94f8964dd7685.28165.1510797991000000.lz4 (inaccessible)
       Message: Process 28165 (php-fpm) of user 0 dumped core.
                
                Stack trace of thread 28165:
                #0  0x00007f5728d8e48e pthread_rwlock_init (libpthread.so.0)
                #1  0x00007f5714191480 apc_lock_create (apcu.so)
                #2  0x00007f5714195f34 apc_sma_api_init (apcu.so)
                #3  0x00007f57141923b7 zm_startup_apcu (apcu.so)
                #4  0x000056251973b0c4 zend_startup_module_ex (php-fpm)
                #5  0x000056251973b19c zend_startup_module_zval (php-fpm)
                #6  0x0000562519748b6a zend_hash_apply (php-fpm)
                #7  0x000056251973b48a zend_startup_modules (php-fpm)
                #8  0x00005625196d2b93 php_module_startup (php-fpm)
                #9  0x00005625197e68c5 php_cgi_startup (php-fpm)
                #10 0x00005625195aa160 main (php-fpm)
                #11 0x00007f57291c503a __libc_start_main (libc.so.6)
                #12 0x00005625195ab63a _start (php-fpm)