Re: Fix to bootstrap

[Jim Meyering]

Reuben Thomas wrote:
> On 19 April 2012 14:28, Jim Meyering <address@hidden> wrote:
>>
>> Thanks for tracking that down.
>> However, rather than handling just that one "cd",
>> how about ensuring that no use of "cd" in this script
>> can cause such trouble?  To do that, you would unset CDPATH
>> somewhere near the top, with a comment explaining its purpose.
>
> That would not deal with "cd -". It also assumes that CDPATH would
> never be relied on.

bootstrap will never use "cd -",
and portable scripts should not rely on CDPATH.

> Currently there are two uses of cd in bootstrap, only one of which
> (the one I fixed) has its output used.

The idea is to make the code a little more future/maintenance proof.
If we leave it so "cd" might in some unusual cases (like yours)
generate output, a new use of "cd" might also be in a place
that can cause malfunction.  Unsetting CDPATH protects against that,
while addressing only the particular "cd" that hurts today does not.

> To make the intention clear, it would seem more sensible to have some
> sort of wrapper (function? script?) for cd which never produces
> output. Or is that overkill? (Arguably, it's a misfeature of cd.)
>
> Anyway, I leave those more complex issues to you; you can take my fix
> for now or adapt it as you see fit.

I've fixed it with this:

>From 28c2a36d502603738c26d59f7d9bd16f27010835 Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Thu, 19 Apr 2012 16:02:23 +0200
Subject: [PATCH] bootstrap: don't let a user's CDPATH setting affect this
 script

When CDPATH is set, cd will sometimes generate output.
When "cd" is run in a subshell whose output matters, that
surprising-to-some output can cause malfunction.
Unsetting CDPATH turns off this shell "feature."
* build-aux/bootstrap (CDPATH): Unset.
Reported by Reuben Thomas in:
http://thread.gmane.org/gmane.comp.lib.gnulib.bugs/30435
and inspired by his patch here:
http://thread.gmane.org/gmane.comp.lib.gnulib.bugs/30440
---
 ChangeLog           |   13 +++++++++++++
 build-aux/bootstrap |    6 +++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index c980aa3..693ad24 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,16 @@
+2012-04-19  Jim Meyering  <address@hidden>
+
+       bootstrap: don't let a user's CDPATH setting affect this script
+       When CDPATH is set, cd will sometimes generate output.
+       When "cd" is run in a subshell whose output matters, that
+       surprising-to-some output can cause malfunction.
+       Unsetting CDPATH turns off this shell "feature."
+       * build-aux/bootstrap (CDPATH): Unset.
+       Reported by Reuben Thomas in:
+       http://thread.gmane.org/gmane.comp.lib.gnulib.bugs/30435
+       and inspired by his patch here:
+       http://thread.gmane.org/gmane.comp.lib.gnulib.bugs/30440
+
 2012-04-16  Akim Demaille  <address@hidden>
        and Jim Meyering  <address@hidden>

diff --git a/build-aux/bootstrap b/build-aux/bootstrap
index 16dc15c..4afc6c4 100755
--- a/build-aux/bootstrap
+++ b/build-aux/bootstrap
@@ -1,6 +1,6 @@
 #! /bin/sh
 # Print a version string.
-scriptversion=2012-04-16.16; # UTC
+scriptversion=2012-04-19.14; # UTC

 # Bootstrap this package from checked-out sources.

@@ -36,6 +36,10 @@ nl='
 LC_ALL=C
 export LC_ALL

+# Ensure that CDPATH is not set.  Otherwise, the output from cd
+# would cause trouble in at least one use below.
+(unset CDPATH) >/dev/null 2>&1 && unset CDPATH
+
 local_gl_dir=gl

 me=$0
--
1.7.10.208.gb4267