WSOD while sending headers, probably Cache-related I have a very strange problem with a fresh Drupal install: On some pages, I receive a WSOD with ERR_EMPTY_RESPONSE: 



It happens for instance when on admin/config/development/performance I click Clear all caches. (But also other pages are affected – for instance the Layout Builder page of a Node type.)

Interestingly, I could isolate the bug down here: If in vendor/symfony/http-foundation/Response.php::sendHeaders() I tweak the code so that it unsets a lot of the headers to be sent (actually, all of them but X-Generator and X-Frame-Options), the error disappears.

...
$headers = $this-&gt;headers-&gt;allPreserveCaseWithoutCookies();
unset($headers['Cache-Control']);
unset($headers['Content-language']);
unset($headers['Date']);
unset($headers['X-Drupal-Dynamic-Cache']);
unset($headers['X-UA-Compatible']);
unset($headers['X-Content-Type-Options']);
unset($headers['Expires']);
unset($headers['Vary']);
foreach ($headers as $name =&gt; $values) {
  ... 


Based on the headers I unset, it seems that it is a caching-related problem. (However, Caching is switched off, Browser and proxy cache maximum age is set to &lt;no caching&gt;.)

My setup:


installed Drupal 8.7.5 via composer
on my local machine, a MacBook Pro with macOS High Sierra
installed via Homebrew


PHP 7.3
Apache 2.4
MySQL 5.7.24



Any idea what the problem might be?

Edit: Regarding Apache error logs: I first had no entries there but now I debugged again and saw such one:

[core:notice] [pid 92592] AH00052: child pid 98466 exit signal Bus error (10)


Googling gave the suggestion to apc_clear_cache(); but it's not available in PHP7. So I ran opcache-reset().

Result: Problem is still there, now already when opening the page admin/config/development/performance.

Now the error logs say:

 [core:notice] [pid 7428] AH00052: child pid 7446 exit signal Segmentation fault


Google suggests this is likely  caused by a syntax error in php.ini or some included extension there. Thus I have taken out all extensions, including

zend_extension=/usr/local/opt/php/lib/php/20180731/opcache.so


but the problem remains.

Edit 2: Here's the output of my php -i (It uses the same php.ini file as phpinfo() in localhost). https://pastebin.com/ppvCpPA6
Now I could solve it myself. My Apache error logs did show

AH00052: child pid 7363 exit signal Segmentation fault (11)


so it must have been a problem with the Apache config.

I took the opportunity to reinstall Apache and configure it with FCGI/FPM according to this and now the problem is gone.