Re: Progress on using FvwmButtons (and some questions)

[Klaus Schilling <Klaus.Schilling@home.ivm.de>]

Greg Badros writes:
 > 
 > 
 > <For the guile list that I'm now cc'ing, this is a thread from
 > scwm-discuss about avoiding bugs where a long/int is used where an SCM
 > was meant to be used -- inspired by a hard-to-find bug in Scwm due to
 > SCM being typedefed to long>
 > 
 > Maciej Stachowiak <mstachow@mit.edu> writes:
 > 
 > > Not all SCMs are actually pointers, characters and integers up to 30
 > > bits are stored directly in that word, with a type tag. One could come
 > > up with an assertion based on the possible values of the type tags,
 > > but this would be pretty complicated.

Is that the difference between IMP and NIMP that has to be observed when
writing typechecks for wrapper code? 

 > 
 > Which is why we have abstractions like macros and functions.  From a
 > quick look at tags.h, it looks as though the valid SCM values are sparse
 > enough and well-defined enough that perhaps a macro for validating SCMs
 > could be written.  Then asserting the validity of all SCMs at function
 > calls in a debug build might help catch some errors dynamically.
 > Obviously I'd prefer a solution that got us this statically, but it
 > sounds like that would require more pervasive changes to guile.

How is it solved in other scheme implementations?

       Klaus schilling