Re: string manipulation : removing a part of a string

[Vincent Torri]

On Thu, 14 Jun 2012, Eric Blake wrote:

> On 06/14/2012 05:36 PM, Vincent Torri wrote:
> > Hey
> >
> > I pass -Wno-foo as a parameter of an m4 macro. What I would like is to
> > store into a variable -Wfoo, so removing 'no-'
> >
> > Is it possible with the m4 macro string manipulation ? If not, what's
> > the best solution ?
>
> m4_bpatsubst([[$1]], [no-])
>
> will delete the first instance of the regular expression 'no-' (if any)
> from parameter $1.  Yes, the first argument is double-quoted, so that
> the output of m4_bpatsubst will still be single-quoted.
>
> > Another related question: if I pass -Wbar, I would like to know if it
> > begins by '-Wno-'. How can I do that with m4 ?
>
> m4_if(m4_index([$1], [-Wno-]), 0, [yes...], [no...])

I try that to set flagm4 to -Wfoo if tmp is -Wno-foo, but it seems 
that i don't use correctly the m4 macros

m4_if(m4_index([$tmp], [-Wno-]), 0, [m4_define([flagm4], 
[m4_bpatsubst([[$tmp]], [no-])])], [m4_define([flagm4], [$tmp])])

do you have an idea ?

thank you

Vincent Torri