question about proton error philosophy
I was expecting errno inside the messenger to be reset to 0 at the end of any successful API call. It isn't: instead it looks like the idea is that errno preserves the most recent error that happened, regardless of how long ago that might be. Is this intentional? I am having a hard time understanding why we would not want errno to always represent the messenger state as of the completion of the most recent API call. I would be happy to submit a patch to make it work this way, and see what people think - but not if I am merely exhibiting my own philosophical ignorance here.
Re: question about proton error philosophy
No, you're right. errno is never set to zero by any system call or library function ( That's from Linux doco. ) OK, I was just philosophically challenged. I think what confused me was the line in the current Proton C doc (about errno) that says an error code or zero if there is no error. I'll just remove that line. OK, I withdraw the question. ( I still don't like this philosophy, but the whole world is using it, and the whole world is bigger than I am... ) - Original Message - Do other APIs reset the errno? I could have sworn they didn't. On Mon, Sep 16, 2013 at 12:01 PM, Michael Goulish mgoul...@redhat.com wrote: I was expecting errno inside the messenger to be reset to 0 at the end of any successful API call. It isn't: instead it looks like the idea is that errno preserves the most recent error that happened, regardless of how long ago that might be. Is this intentional? I am having a hard time understanding why we would not want errno to always represent the messenger state as of the completion of the most recent API call. I would be happy to submit a patch to make it work this way, and see what people think - but not if I am merely exhibiting my own philosophical ignorance here. -- Hiram Chirino Engineering | Red Hat, Inc. hchir...@redhat.com | fusesource.com | redhat.com skype: hiramchirino | twitter: @hiramchirino blog: Hiram Chirino's Bit Mojo
Re: question about proton error philosophy
On Mon, Sep 16, 2013 at 12:33:29PM -0400, Hiram Chirino wrote: Do other APIs reset the errno? I could have sworn they didn't. Successful system calls and library functions never reset errno to 0, so this variable may have a nonzero value as a consequence of an error from a previous call. Furthermore, SUSv3 permits a successful function call to set errno to a nonzero value (although few functions do this). Therefore, when checking for an error, we should always first check if the function return value indicates an error, and only then examine errno to determine the cause of the error. - The Linux Programming Interface, pg 49. -- Darryl L. Pierce, Sr. Software Engineer @ Red Hat, Inc. Delivering value year after year. Red Hat ranks #1 in value among software vendors. http://www.redhat.com/promo/vendor/ pgpEFRS5MxPIW.pgp Description: PGP signature
Re: question about proton error philosophy
Do other APIs reset the errno? I could have sworn they didn't. On Mon, Sep 16, 2013 at 12:01 PM, Michael Goulish mgoul...@redhat.com wrote: I was expecting errno inside the messenger to be reset to 0 at the end of any successful API call. It isn't: instead it looks like the idea is that errno preserves the most recent error that happened, regardless of how long ago that might be. Is this intentional? I am having a hard time understanding why we would not want errno to always represent the messenger state as of the completion of the most recent API call. I would be happy to submit a patch to make it work this way, and see what people think - but not if I am merely exhibiting my own philosophical ignorance here. -- Hiram Chirino Engineering | Red Hat, Inc. hchir...@redhat.com | fusesource.com | redhat.com skype: hiramchirino | twitter: @hiramchirino blog: Hiram Chirino's Bit Mojo
