Re: string manipulation : removing a part of a string

[Vincent Torri]

On Mon, 18 Jun 2012, Eric Blake wrote:

> On 06/15/2012 11:49 PM, Vincent Torri wrote:
>
> > > This can be shortened:
> > >
> > > m4_pushdef([flagm4], m4_bpatsubst([[$2]], [no-]))
> > >
> > > since m4_bpatsubst is a no-op if the pattern 'no-' doesn't appear.
>
> > heh, as option=m4_bpatsubst([[$2]], [no-]) is working, there's no need.
> > It's so simple when you know how it works...
> >
> > I finally found the doc of that m4 macro, and it's not mentioned that
> > it's a no op in some cases:
> >
> > http://www.gnu.org/software/autoconf/manual/autoconf.html#Conditional-constructs
> >
> >
> > is it possible to add that ?
>
> Patches welcome, if you think it would help.  The current documentation
> for m4_bpatsubst() just points to the GNU M4 manual for patsubst():
> https://www.gnu.org/software/autoconf/manual/autoconf.html#Redefined-M4-Macros

the patsubst() doc seems sufficient, actually :

http://uw714doc.sco.com/cgi-bin/info2html?%28m4%29Patsubst&lang=en

> > Also, if I'm not mistaken, there's a typo in the macro name :
> >
> > m4_bpatsubsts (final s)
> >             ^
>
> Wrong macro.  m4_bpatsubsts() with the final s is a different macro,
> with even more power than m4_bpatsubst().

haa, ok

> > > m4_foreach_w([flag], [$2],
> > > [EFL_CHECK_COMPILER_FLAG([$1], m4_defn([flag]))])
> >
> > for $1, i was sure, but why is it not needed for m4_defn([flag]) ?
>
> Because you _want_ the m4_defn() to be expanded up front, and because
> the output of m4_defn is already quoted for reuse.  In other words, you
> want to call:
>
> EFL_CHECK_COMPILER_FLAG([efl], [-Wfoo])
> EFL_CHECK_COMPILER_FLAG([efl], [-Wno-bar])
>
> and not:
>
> EFL_CHECK_COMPILER_FLAG([efl], [m4_defn([flag])])
> EFL_CHECK_COMPILER_FLAG([efl], [m4_defn([flag])])
>
> because the latter wouldn't be checking the right flag names.

ok, thank you !

Vincent Torri