Re: [PATCH] Replacement for the sigs_to_ignore hack in timeout.c

[Bruno Haible]

Jim Meyering wrote:
> > the change I could apply is to add a comment in the specification:
> > "This function assumes that the signal handler for SIGCHLD is not set to
> > SIG_IGN."
> 
> Thanks.  That's probably all that it can do.

Done, see below.

> Though isn't it better to say it assumes the handler *is* set to SIG_DFL?

Why? When the signal handler is set to a function, wait_subprocess should
work, according to the description of waitpid() in POSIX.

> wait-process.c could print
> a diagnostic about the potential portability problem when it
> sees the SIGCHLD handler is not SIG_DFL.  Or return a value
> indicating the problem -- esp. if it already knows it's running
> on a system with the losing semantics.

Currently, when the problem occurs, it will print a diagnostic:
  <subprogram> subprocess: No child processes
This should be enough, I think.



2009-02-28  Bruno Haible  <address@hidden>

        * lib/wait-process.h (wait_subprocess): Clarify restriction regarding
        SIGCHLD.
        Reported by Jim Meyering.

--- lib/wait-process.h.orig     2009-02-28 17:40:00.000000000 +0100
+++ lib/wait-process.h  2009-02-28 17:39:40.000000000 +0100
@@ -1,5 +1,5 @@
 /* Waiting for a subprocess to finish.
-   Copyright (C) 2001-2003, 2006, 2008 Free Software Foundation, Inc.
+   Copyright (C) 2001-2003, 2006, 2008-2009 Free Software Foundation, Inc.
    Written by Bruno Haible <address@hidden>, 2001.
 
    This program is free software: you can redistribute it and/or modify
@@ -50,7 +50,9 @@
      with an error status.
    - If termsigp is not NULL, *termsig will be set to the signal that
      terminated the subprocess (if supported by the platform: not on native
-     Windows platforms), otherwise 0.  */
+     Windows platforms), otherwise 0.
+   Prerequisites: The signal handler for SIGCHLD should not be set to SIG_IGN,
+   otherwise this function will not work.  */
 extern int wait_subprocess (pid_t child, const char *progname,
                            bool ignore_sigpipe, bool null_stderr,
                            bool slave_process, bool exit_on_error,