Re: [Libguestfs] Further nbdkit patches for Haiku
On 11/13/18 7:40 AM, Richard W.M. Jones wrote:
> (I think the error message is "incorrect ELF header")
could be
> something to do with the way we use shebangs (#!). IIRC this also
> fails on FreeBSD so probably nbdkit is doing something which is not
> correct POSIX.
POSIX says that #! shebangs are undefined behavior. You're at the mercy
of each operating system, because there is no portable solution across
all systems.
I reproduced this on FreeBSD. The path used in the tests is indeed
relative:
#!../nbdkit
However replacing this with an absolute path did *not* fix the issue.
FreeBSD seems to not like running a shell script from a shebang,
probably because this is (was?) insecure. However because of the way
our test harness works we really need to run the shell script. As
there seems to be no simple way to fix this for now, I left the bug in
1.8.0.
Can you use '#!/bin/sh /path/to/nbdkit'? That way, the shebang is
running a binary (not a script), where the binary in turn runs the
desired script? Or does that run into other limitations (for example,
#! can only portably used with exactly one argument after the
interpreter name; BSD and more recently coreutils have added 'env -S' to
work around that limitation, although it is not yet widespread
portable). But yes, I do seem to recall that #! must point to a binary
interpreter rather than a script of an unspecified language (the fact
that Linux will happily run a script under /bin/sh is not universal).
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
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