Re: misc/23729 (please add a FAQ on the 'Syntax error: "(" unexpected' ld.so issue)

[Robert Elz <kre%munnari.OZ.AU@localhost>]

The following reply was made to PR misc/23729; it has been noted by GNATS.

From: Robert Elz <kre%munnari.OZ.AU@localhost>
To: matthew green <mrg%eterna.com.au@localhost>
Cc: gnats-bugs%netbsd.org@localhost, misc-bug-people%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost,
        gnats-admin%netbsd.org@localhost, refling%acm.org@localhost
Subject: Re: misc/23729 (please add a FAQ on the 'Syntax error: "(" unexpected' ld.so issue)
Date: Fri, 17 Jun 2022 21:47:30 +0700

     Date:        Fri, 17 Jun 2022 15:40:21 +1000
     From:        matthew green <mrg%eterna.com.au@localhost>
     Message-ID:  <6302.1655444421%splode.eterna.com.au@localhost>
 
   | space-bird ~> /bin/sh /bin/sh
   | /bin/sh: Cannot execute ELF binary /bin/sh
 
 hmmm  ... that looks like  a bug.  If run that way, the shell
 should try to run it, just like all the other shells you tried
 did.  POSIX does make it undefined/unspecified what happens
 when there are any \0's in any part of the script that could be
 executed (ie: not counting random data that may followw) so
 we are probably technically conformant, but that still seems
 wrong.
 
 I will, however, resist fixing it fir a few days to see what
 others think.
 
 The issue in the PR (which is not really about this problem
 at all) concerns seemingly sane, executable, commands - typically
 found via a PATH search, though not always - for which exec()
 fails with ENOEXEC - which shells from the ancient past, long before
 #! was invented, have always treated as meaning "command is a sh
 script", and so simply opened and tried to parse that way.
 
 That is still required by POSIX (which does not have #!), but
 they do now permit the shell to use a heuristic to guess
 whether the file really is a script or not.
 
 Most shells implement such a test now (but less did when this
 PR was filed .. POSIX didn't allow it then) so the problem
 reported occurs far less often than it did (it is still not
 well handked).
 
 kre