Re: cc-vars.el

[storm@cua.dk (Kim F. Storm)]

"Stefan Monnier" <monnier+gnu/emacs@rum.cs.yale.edu> writes:

> 
> But I also completely agree that we should try to make sure that pragmas
> as needed as rarely as possible, so I wholeheartedly support Dave's
> suggestion which will at least reduce the amount of useless warnings.
> 

One of the problems I've seen is with code which is conditioned to
differentiate between either gnu emacs and xemacs, or between different
os-types.

In the first case, many packages seem to have their own "xyz-xemacs-p"
function or variable, and the bytecompiler will surely have a hard time
determining whether a piece of code isn't used at all on this platform.

A new built-in variable `emacs-type' (value = 'gnu-emacs or e.g. 'xemacs)
would fix this problem; for portability, packages may add the following snippet
to support older versions of gnu and xemacs:

        (unless (boundp 'emacs-type)
          (setq emacs-type
             (cond ((string-match "XEmacs" (emacs-version)) 'xemacs)
                   (t 'gnu-emacs))))

In this case, I think it is ok for the byte-compiler to simply ignore
all errors in the "other type of emacs" branch.

In the second case, code may do one of the following:
        (if (eq system-type 'msdos)  ;; or using cond
           (msdos-function ...))

or
        (if (fboundp 'msdos-function)
           (msdos-function ...))

The problem here is that the byte-compiled file must actually work on
msdos even when byte-compiled on, say, gnu/linux.  Maybe we could add
a list of prototypes for built-in platform specific functions in the
byte-compiler.

-- 
Kim F. Storm <storm@cua.dk> http://www.cua.dk