On 07/18/2012 02:23 PM, Andreas Schwab wrote: > Eric Blake <ebl...@redhat.com> writes: > >> We need to document this issue if we decide this is important enough to >> fix in autoconf. But a patch for this issue seems like a reasonable >> improvement to me. Would you like to help write one? > > How about this? > > Andreas. > >>From e45f558825d68ae898153c33c710ac377016fc8d Mon Sep 17 00:00:00 2001 > From: Andreas Schwab <sch...@linux-m68k.org> > Date: Tue, 22 Nov 2011 00:36:46 +0100 > Subject: [PATCH] general: Sanitize IFS in EXIT trap > > IFS may be modified temporarily when the configure script receives a > signal. Make sure the EXIT trap uses the standard value. > > * lib/autoconf/general.m4: Sanitize IFS in trap.
I like it, and pushed. I also tweaked your listing in THANKS, assuming
you prefer a newer email address these days. I think it's also worth a
mention in the docs, so I'll follow up with:
From 9debc540b081488f92a71d0850736786ec2d92c8 Mon Sep 17 00:00:00 2001
From: Eric Blake <ebl...@redhat.com>
Date: Wed, 18 Jul 2012 14:53:24 -0600
Subject: [PATCH] doc: mention trap pitfalls
Document why the previous patch was useful.
* doc/autoconf.texi (Limitations of Builtins) <trap>: Mention the
need to be defensive in trap handlers.
---
doc/autoconf.texi | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 506d966..0dd4898 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -18346,6 +18346,18 @@ Limitations of Builtins
2
@end example
+Be aware that a trap can be called from any number of places in your
+script, and therefore the trap handler should not make assumptions about
+shell state. For some examples, if your script temporarily modifies
+@env{IFS}, then the trap should include an initialization back to its
+typical value of space-tab-newline (autoconf does this for generated
+@file{configure} files). Likewise, if your script changes the current
+working directory at some point after the trap is installed, then your
+trap cannot assume which directory it is in, and should begin by
+changing directories to an absolute path if that is important to the
+cleanup efforts (autotest does this for generated @file{testsuite}
+files).
+
@item @command{true}
@c -----------------
@prindex @command{true}
--
1.7.10.4
--
Eric Blake ebl...@redhat.com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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