Re: function-local variables in ltmain

[Gary V. Vaughan]

Hallo Ralf,

Ralf Wildenhues wrote:
> Hi Albert,
>
> * Albert Chin wrote on Sat, Aug 13, 2005 at 09:56:43PM CEST:
>
> > On Sat, Aug 13, 2005 at 10:40:01AM +0200, Ralf Wildenhues wrote:
> >
> > > Gary once mentioned a plan to emulate local variables in m4sh.

Indeed I did; and for exactly the reasons you enumerate below!  Thanks 
for raising it again.

> > > 2) This looks somewhat ugly in the output, but to a certain extent, it
> > > is possible to emulate local variables with m4sh: see below.
> >
> > Way ugly.
>
> Yep.

That doesn't matter.  The output of gcc is ugly too!  We should be 
maintaining the source files (.m4sh), and anything that makes them 
easier to read and edit is a good thing.

> > Just seems to make libtool harder to maintain.

Au contraire.  Once any such mechanism has been debugged, it makes 
libtool easier to maintain... as has been the case with several of the 
refactorings I've done as we progress towards 2.0.

> > What's the point anyway? To keep function-specific variables from
> > being clobbered? Was this so much of a problem before libtool had
> > functions and everything was global? Seems like a solution looking for
> > a problem. 
>
> Well, I would like to modularize it more.  I am pretty sure it can be
> made shorter and easier to understand that way.  (See func_execute_cmds
> or func_source for example). For this, all-global variables are a
> problem to some extent.

Agreed.

> Just look at two examples: func_extract_archives uses variables named
> my_*.  This is not safe: both its caller and any functions it may call
> itself may overwrite these accidentally.  func_extract_an_archive OTOH
> uses safe names f_ex_an_ar_*, but is ugly to the point of being
> unreadable.

maintain an m4 map of function name to enumeration encoding, and name 
the local variables localxx_var_name if output ugliness is a big issue. 
 On the principle of looking at the .m4sh files way more often than the 
generated libtool script, I don't think it is worth the trouble.

> I do _not_ want to eliminate use of globals.  All I want is an easier
> method for ensuring this than regular grepping of the whole script.
> I'm certainly not determined to use this particular idea.

I am :-)  Eventually.  In my copious free time ;-)

Cheers,
        Gary.
--
Gary V. Vaughan      ())_.  address@hidden,gnu.org}
Research Scientist   ( '/   http://tkd.kicks-ass.net
GNU Hacker           / )=   http://www.gnu.org/software/libtool
Technical Author   `(_~)_   http://sources.redhat.com/autobook

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