strace and sigprocmask

[Christopher Faylor]

On Fri, May 09, 2014 at 01:55:51PM +0100, Henry S. Thompson wrote:
>Running on Windows 8.1, with 32-bit Cygwin v1.7.29.
>
>I've taken straces of a problematic area of xemacs, tidied them, and
>am trying to locate significant differences.
>
>I'm seeing something I don't understand, which isn't causing a crash
>so probably isn't significant, but I'd like to understand it better.
>
>strace 1 has:
> [main] PID1  sigprocmask:  0   =   sigprocmask(2647444,   0xNULL, 0xNULL)
>where strace 2 has:
> [main] PID1  sigprocmask:  0   =   sigprocmask(2649272,   0xNULL, 0xADDR)
>
>Similar lines appear frequently in both straces.
>
>Either I don't understand strace output, or this is bizarre -- the
>first arg to sigprocmask should always be 0, 1 or 2, right?
>
>I'd welcome any help in understanding how I should be reading this,
>and more generally, how I could have found the answer to my question
>myself.

This is a a bug (now fixed) in the source.  The first argument to
sigprocmask was not being sent to the strace printf, pushing all of the
arguments left.

As to how you could have found the answer, it's the standard answer for
free software projects - look at the source.

cgf

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