Crashes in cmake subprocesses since 3.6.0

[Takashi Yano]

On Thu, 3 Apr 2025 12:32:35 +0900
Takashi Yano wrote:
> > Still, I wonder in which thread raw_write is running during fork().
> 
> Weird enough, raw_write() is called in the main thread (_main_tls).
> Any chance, fixup_after_fork() is not called?

It seems that raw_write() is called before returning from
pthread::atforkchild() in fork::child().

Moving _my_tls.fixup_after_fork() before atforkchild() seems
to solve the issue.

What about:
ld_preload ();
fixup_hooks_after_fork ();
ch.rd_proc_pipe = ch.wr_proc_pipe = NULL;
?

Should any of these be before pthread::atforkchild() asl well?

I'm now performing a long-run test with the patch:

diff --git a/winsup/cygwin/fork.cc b/winsup/cygwin/fork.cc
index 0742ab363..28daf2682 100644
--- a/winsup/cygwin/fork.cc
+++ b/winsup/cygwin/fork.cc
@@ -187,7 +187,6 @@ frok::child (volatile char * volatile here)
 
   ForceCloseHandle1 (fork_info->forker_finished, forker_finished);
 
-  pthread::atforkchild ();
   cygbench ("fork-child");
   ld_preload ();
   fixup_hooks_after_fork ();
@@ -196,6 +195,7 @@ frok::child (volatile char * volatile here)
      rd_proc_pipe that would be an invalid handle.  In the case of
      wr_proc_pipe it would be == my_wr_proc_pipe.  Both would be bad. */
   ch.rd_proc_pipe = ch.wr_proc_pipe = NULL;
+  pthread::atforkchild ();
   CloseHandle (hParent);
   hParent = NULL;
   cygwin_finished_initializing = true;

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>