Date: Tue, 9 Jan 2018 13:03:47 -0500 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: Conformance problem in system() On Sun, Dec 31, 2017 at 12:23:42AM +0100, Markus Wichmann wrote: > On Sat, Dec 30, 2017 at 05:22:04PM -0500, Rich Felker wrote: > > I think you're right that there's a problem here, but I don't think > > the patch correctly or fully fixes it. A simpler version of what > > you're doing would be to just initialize status to -1 instead of > > 0x7f00, since your patch is returning -1 in all cases where waitpid > > did not complete successfully. But that ignores the POSIX requirement > > to behave as if the interpreter exited with status 127 when it was > > possibel to make the child process but the command interpreter could > > not be executed. > > > > Actually, I noticed another problem: waitpid() returns the PID of the > changed child process on success, so the > > if (wr) status = wr; > > should be > > if (wr < 0) status = wr; > > The initialization of status would only change something if the kernel > did not write to status on waitpid() failure. Is that guarenteed ABI, or > does this just happen to be the case on current kernels? > > > musl's posix_spawn does not succeed when exec fails in the child; > > instead the exec error is returned. This behavior is permitted but not > > required by POSIX. I think it would actually be preferable to system > > to return -1 and set errno in this case too, but POSIX doesn't seem to > > allow that. > > Actually, the requirement to return exit status 127 on exec failure > sounds mighty specific to me. As if someone wanted to codify behavior > they needed in their utility. Which means there may be software out > there that depends on this behavior. > > There is the possibility of not considering a posix_spawn()ed child > process as "created" unless posix_spawn() itself did return success, > though. But that might run counter to what the POSIX was going for, > here. I think this is an acceptable interpretation for now. So just changing default initialization of status to -1 should work, right? Rich
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