Web lists-archives.com

Re: Bug: Synchronous signals broken on Cygwin 64




On 4/26/2018 9:57 AM, Thomas Zimmermann wrote:
Hello mailing list,

I noticed that synchronous signals (e.g., SIGSEGV, SIGFPE) appear to be
broken on 64-bit Cygwin systems. I could not find additional information
on the mailing list. If this is not already a known problem, you'll find
some analysis below.


I use Cygwin DLL 2.10 with all packages up-to-date. My test system runs
Windows 7.


The expected behavior is that an installed signal handler runs exactly
once for a signal and the OS terminates the program if the handler
returns. This works on 32-bit Cygwin. From my observation, Cygwin 64
differs in the follow ways:

1) Generating a synchronous signal on the main thread, makes the signal
handler enter an endless loop. The attached test 'syncsig.c' illustrates
this.

2) Generating a synchronous signal on an additional POSIX thread ignores
the installed signal handler entirely. The handler does not run and the
program gets terminated immediately. The attached test 'syncsig_mt.c'
illustrates this.


As mentioned, both cases work correctly on 32-bit installations. I
cannot point to the exact location of the problem, but it appears that
the Cygwin exception-handler code is not set up by 64-bit code.

In case 2) I can see the Windows function KiUserExceptionDispatcher()
being executed for the synchronous signal on the affected thread. This
should lead to a call to the Cygwin exception handler. It does for
32-bit, but not for 64-bit code.

just for confirmation, same results and discrepancies on my W7

 From what I've seen, the exception handler is installed in the c'tor
exception::exception(). [exception.cc:138] The only invocation I found
was in SetThreadName(). [miscfuncs.cc:951] This set-up code is 32-bit-only.


BTW, is there a bug tracker for Cygwin? I'd open a bug report there, or
add the information to an existing one.

there is no bug tracker. Bugs are managed on this mailing list.


Best regards
Thomas


Regards
Marco

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple