On May 31 15:21, Erik Bray wrote: > Hi all, > > I recently ran into a tricky problem when working with cysignals [1] > on Cygwin: Cysignals provides signal handlers for code written in C > or Cython running in a Python interpreter, which converts otherwise > unhandled signals into Python exceptions. > > It recently started using sigaltstack [2] to provide an alternate > stack to run signal handlers on, specifically for SIGSEGV (in case the > cause thereof was a stack overflow). > > Cygwin supports this in principle, but things get pretty flaky at that > point, because if any exception occurs while running on an altstack, > Cygwin will handle it if the exception came from Cygwin itself, but > not otherwise, per this note [3] > > > TODO: What we do here is to handle only __try/__except blocks in Cygwin. > > "Normal" exceptions will simply exit the process. Still, better > > than nothing... */ > > Is that really better than nothing though? The result is that the > process dies with a (Cygwin) exit code of 0. This is quite > surprising! Even if there were really nothing else to be done I > wonder if Cygwin could try as hard as possible to at least set a > non-zero exit code in this case. > > Now, it's true what comment above that says: > > > normal SEH handlers are skipped, because the OS exception > > handling considers the current (alternate) stack "broken" > > However, I was able to work around this in cysignals [4] by adding a > VectoredContinueHandler which, in this case, is at least able to > convert the exception code to the appropriate POSIX return code and > exit the process. And superficially it seems to work quite reliably. > But I wonder if there isn't something "wrong" about this from the > Cygwin perspective, and if it shouldn't at least try to do the same...
Good point. I'm not sure I have time to look into this for the time being, but I'm not at all opposed to patches in this area. Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Maintainer cygwin AT cygwin DOT com Red Hat
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