Re: Findutils failure due to reliance /bin/echo

[James Youngman]

[ CC += address@hidden ]

On Wed, May 5, 2010 at 3:53 PM, Ludovic Courtès <address@hidden> wrote:
> Hi James,
>
> James Youngman <address@hidden> writes:
>
>> On Wed, May 5, 2010 at 9:35 AM, Ludovic Courtès <address@hidden> wrote:
>>> Hi James,
>>>
>>> Hydra Build Daemon <address@hidden> writes:
>>>
>>>> FAIL: l1, unexpected failure, child process exited abnormally, 
>>>> /tmp/nix-build-iqdrm25mpg40iivc59hjmdjjay1rfifp-findutils-4.5.10-git.drv-0/findutils-4.5.10-git/xargs/testsuite/../xargs:
>>>>  /bin/echo: No such file or directory
>>>
>>> This is due to the fact that there’s no /bin/echo in the build
>>> environment (actually /bin on NixOS contains only /bin/sh).
>>>
>>> If you want to rely on ‘echo’ other than the shell’s built-in, you
>>> should use AC_PATH_PROG([echo]) in ‘configure.ac’ or something similar.
>>> (Though I can’t think of any reason why the shell built-in wouldn’t
>>> work.)
>>
>> Well, the shell builtin can never work because you can't exec it.
>> POSIX requires xargs to run echo, though:
>>
>> utility
>>     The name of the utility to be invoked, found by search path using
>> the PATH environment variable, described in the Base Definitions
>> volume of IEEE Std 1003.1-2001, Chapter 8, Environment Variables. If
>> utility is omitted, the default shall be the echo utility. If the
>> utility operand names any of the special built-in utilities in Special
>> Built-In Utilities , the results are undefined.
>>
>> So essentially, the echo binary is a runtime dependency for findutils.
>
> Understood, thanks for explaining.
>
> Still, ‘AC_PATH_PROG([ECHO], [echo])’ and then referring to @ECHO@
> instead of /bin/echo in xargs.in.c would remove this path assumption.
>
> What do you think?

The idea makes me very nervous indeed.   Implementing things that way
would mean that the built xargs would fossilise the effect of whatever
setting was in $PATH at the time xargs is built.   This could give
rise to odd surprises (and differences from long-standing behaviour)
for some people.  An alternative would be to use execvp on an
unqualified program name and have the invoked version of echo be
sensitive to the user's $PATH value.  Of course that will also
potentially produce not-immediately-obvious inconsistencies of
behaviour.

As far as I can tell, there is no requirement in POSIX or the SVID
which would require "echo" to live in a particular directory, and none
which would require xargs to expect echo to live in /bin.

However, I'm still very reluctant to change such a long-held property,
and most certainly not without a great deal of advance warning.

James.