Re: Fix `set -o posix' again

[Ralf Wildenhues]

Hello Paul, Howard, Bruce,

This issue is not solved: a few days ago I encountered it on a different
AIX 5.3 system (note Howard reported it for AIX 5.1): I believe I saw
exactly the issues Howard reported, which I did not before.  Now, some
days later, I see yet slightly different issues.  :-/

To tell you the truth, I'm a bit at a loss how to go about this.
I have access to systems to test on, but not a lot of experience,
can neither change system settings nor reboot, nor will I test
stuff if that could endanger production operation.
IOW: help greatly appreciated.

* Paul Eggert wrote on Sat, Jan 21, 2006 at 11:48:03PM CET:
> Ralf Wildenhues <address@hidden> writes:
> 
> >> > | elif (set -o posix) >/dev/null 2>&1; then
> >> > |   set -o posix
> >> > | fi
> >> 
> >> Why does this hang under AIX?  Can you truss it, or strace it, or whatever?
> >
> > D'oh.  It waits for stdin and finishes when given an EOF.

> Does it work if you redirect from stdin?  Something like this?
> 
> elif (set -o posix) </dev/null >/dev/null 2>&1; then
>   set -o posix
> fi

No.  When done like this, `configure' will remain completely silent:
no `checking for..' lines, nothing, but otherwise do its job.

With `((set -o posix))' (isn't that nonportable syntax, by the way?),
configure exits immediately.  I have no idea why, the last truss lines
are
| statx("/tmp", 0x2FF21870, 76, 0)                = 0
| open("/tmp", O_RDONLY)                          = 3
| getdirent(3, 0x20098A18, 4096)                  = 1168
| lseek(3, 0, 0)                                  = 0
| kfcntl(3, F_GETFD, 0x2FF22FFC)                  = 0
| kfcntl(3, F_SETFD, 0x00000001)                  = 0
| getdirent(3, 0x20098A18, 4096)                  = 1168
| getdirent(3, 0x20098A18, 4096)                  = 0
| close(3)                                        = 0
| kwrite(2, " . . / l i b t o o l - 2".., 106)    = 106
| _exit(1)

Running with `sh -x' gives no clue: output stops at the point the
command is encountered.

> I think that would be more efficient than ((set -o posix)).
> 
> >         * lib/m4sugar/m4sh.m4 (_AS_BOURNE_COMPATIBLE): Allow either of
> >         `BASH_VERSION', `KSH_VERSION', or `RANDOM' as indication of ksh
> >         or bash, to set the `posix' option.
> 
> Well, if possible, I'd rather not limit our universe to bash and ksh.
> There might be other shells that have "set -o posix".

Sure.  This shell has neither of BASH_VERSION or KSH_VERSION.  It has
RANDOM, and it presents itself as Version M-11/16/88f.  The pdksh clone
in OpenBSD /bin/sh also has RANDOM, but not KSH_VERSION.

Cheers,
Ralf