[binaryfire]

In builds with --enable-swoole-thread, if the main thread has a Process::signal() handler, the process crashes as soon as any other thread ends:

use Swoole\Process;
use Swoole\Thread;

if (Thread::getArguments()) {
    return;
}
Process::signal(SIGTERM, function () {});
$thread = new Thread(__FILE__, 'child');
$thread->join();
echo "joined\n";

This aborts with zend_mm_heap corrupted before joined. A SWOOLE_THREAD server that sets a handler in onStart crashes the same way when its worker threads exit at shutdown.

Cause

Process::signal() only works on the main thread, but its callbacks are stored in the process-wide signal_fci_caches. Every thread's request shutdown calls php_swoole_process_signal_clean(), which frees all of them through that thread's executor and resets the shared listener count.

Process::start() called from a child thread has the same problem in the new process: the after-fork cleanup frees the inherited callbacks from the wrong heap, and the process aborts before running its callback.

Fix

• Request shutdown skips the signal cleanup outside the main thread. The main thread still frees the callbacks at its own shutdown.
• A process forked from a non-main thread drops the inherited callbacks instead of freeing them. swoole_fork() has already removed their signal handlers.

Non-ZTS builds are unchanged, since sw_is_main_thread() is always true there. php_swoole_runtime_rshutdown() already returns early outside the main thread in the same way.

Tests

tests/swoole_thread/signal_handler_thread_exit.phpt: the main thread registers a SIGTERM handler, a child thread starts a process that must exit cleanly, and after the join the main thread checks its handler still runs. It fails on 6.1, passes with this change, and fails if either change is removed. I also ran the swoole_thread, swoole_process_pool and swoole_process signal and fork tests on a PHP 8.4 ZTS thread build, with no new failures.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.80%. Comparing base (31c8fc6) to head (99bf94c).

Additional details and impacted files

@@            Coverage Diff             @@
##              6.1    #6410      +/-   ##
==========================================
- Coverage   85.81%   85.80%   -0.02%     
==========================================
  Files         110      110              
  Lines       17113    17113              
  Branches     3062     3063       +1     
==========================================
- Hits        14685    14683       -2     
- Misses       2428     2430       +2     

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