[Bug 52302] New: Firefox hangs when loading some URLs (e.g. <https://www.phoronix.com>)

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=52302

Bug ID: 52302
           Summary: Firefox hangs when loading some URLs (e.g.
                    https://www.phoronix.com)
           Product: Wine
           Version: 6.12
          Hardware: x86-64
               URL: https://download-installer.cdn.mozilla.net/pub/firefox
                    /releases/91.4.1esr/win64/en-US/Firefox%20Setup%2091.4
                    .1esr.exe
                OS: Linux
            Status: NEW
          Keywords: download, regression, source
          Severity: normal
          Priority: P2
         Component: winsock
          Assignee: [e-mail]
          Reporter: [e-mail]
   Regression SHA1: 414b31bc0bbbfe005e90a1946a649082dc303c55
      Distribution: ---

Split from bug 51442. Copying the description from comments 11 and 17:

"To reproduce, just go to mail.google.com, possibly login to your gmail
account, browse some mail and the categories on the left. At some point, it
will stop loading as if you're offline. When this happens, no other connections
will work; you can attempt to go to any other website on the URL bar and it
will not connect, but hang indefinitely, once this bug is triggered.

Sometimes, it starts hanging as soon as mail.google.com is loaded, and then of
course no other connection works anymore, but that happens mostly on Firefox
rather than Pale Moon. By "hang" I mean the connections hang, not the rest of
the browser."

and

"This bug can be triggered quite reliably without hitting other bugs with:

firefox.exe -private -devtools https://www.phoronix.com

It is very likely that at least one connection remains stalled a no other
content can be downloaded since then."

It's actually due to a crash; Firefox uses select() and passes an fd_set that
is larger than FD_SETSIZE, which causes our select() implementation to trash
the stack.