Re: "The `-a', `-o', `(', and `)' operands are not portable": please clarify

[Paolo Bonzini]

> What I'd like therefore is a rationale: if -a, -o and parentheses are
> not in POSIX 1990, please say so; if there's some other reason, then
> please give it, and it had better be a good one, because if one cannot
> program to nearly 20-year-old standards, then I begin to wonder what
> the point of prescriptive standards is at all; we may as well give up
> and write descriptive standards instead.

If you write a script with

#! /bin/sh

then yes, you cannot program to _any_ standard.  Autoconf 2.64 is now 
expecting that all systems have _somewhere in the PATH_ a POSIX shell, 
but that need not be /bin/sh.

If you use M4sh, then you have access to almost all useful functionality 
(e.g. shell functions).  You also have wrappers to sanitize incompletely 
specified parts (e.g. AS_ECHO), to work around widely deployed bugs 
(e.g. AS_UNSET, or even in modern shells $LINENO which the Debian dash 
lacks), and to speed up execution when commonly found extensions enable 
it (e.g. AS_VAR_APPEND).

Paolo