Re: Fw: sigwait() breaks when straced

From: Roland McGrath
Date: Sun Jul 31 2005 - 19:05:00 EST

The problem is not really "when straced", but when strace attaches. In
fact, it's not even "when PTRACE_ATTACH'd". It's actually the implicit
SIGSTOP that PTRACE_ATTACH causes. If you simply suspend and resume the
program (with SIGSTOP or C-z), you get the same result. So this report is
more properly identified as "signal stop breaks sigwait".

However, there is in fact no bug here. The test program is just wrong.
sigwait returns zero or an error number, as POSIX specifies. Conversely,
sigtimedwait and sigwaitinfo either return 0 or set errno and return -1.
It is odd that the interfaces of related functions differ in this way,
but they do.


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