Re: [PATCH] init.sh: disqualify shells for which set -x corrupts stderr

[Bruno Haible]

Hi Jim,

> They make it so with "set -x", environment settings
> appear in stderr output.  For example, this command:
>     /bin/sh -c 'set -x; P=1 true 2> err' 2>/dev/null; cat err
> prints "P=1" on those two systems:

This test disqualifies also 'ksh', which is considered the "good"
shell on Solaris, AIX, and a number of other systems:

    I executed the command
       (set -x; P=1 true > inner-out 2> inner-err) > outer-out 2> outer-err
    with a number of shells. Results: inner-out and outer-out were always
    empty, and

                         | inner-err      | outer-err                    |
    ---------------------+----------------+------------------------------+
    Solaris 10 /bin/sh   | P=1            | + true                       |
    ---------------------+----------------+------------------------------+
    ksh-93s              | + P=1          | + true                       |
    Solaris 10 /bin/ksh  |                | + 1> inner-out 2> inner-err  |
    ---------------------+----------------+------------------------------+
    bash 3.2.39          |                | + P=1                        |
                         |                | + true                       |
    ---------------------+----------------+------------------------------+
    dash                 |                | + P=1 true                   |
    ---------------------+----------------+------------------------------+
    zsh 4.3.6            |                | +zsh:3> P=1 +zsh:3> true     |
    ---------------------+----------------+------------------------------+

> the result will be that each init.sh-using test
> will be skipped.

I don't find this a good result.

Observe this:
- Looking at the stderr output of some programs started with environment
  variables happens in some tests, but is not very frequent.
- When you analyze the stderr output of programs, you need to filter out
  all lines that start with '==' also, because these are the marks emitted
  by valgrind.
- When you are at it, you can also filter out all lines that start with
  '+'.
- The only remaining problematic shell is then Solaris 10 /bin/sh,
  which is already disqualified by
     test $(echo y) = y

So, instead of skipping all init.sh based tests on some platforms, I would
propose
  - either to skip only if 'set -x' is enabled; this can be tested by
    test -z "$( (P=1 true 2>&1) 2> /dev/null)"
  - or to handle this problem in each test that analyzes the stderr output
    of some program.

Bruno