[implementations-list] Why can't I byte-compile (all of) Vimpulse?

[Vegard Øye]

> Date: Tue, 27 Apr 2010 20:14:05 +0200
> From: stepnem at gmail.com
>
>> Since the files are to be concatenated, "later" features cannot be
>> required earlier in the code, or the single file complains. So the
>> code has to be laid out in a more linear fashion for compilation to
>> work in all cases.
>
> Actually I'm not sure you should even try to make it work -- isn't the
> current single-file scenario just pathological in this respect?

Quite so, but it's also the preferred distribution format as of
currently. So single-file compilation must work, even if it means
struggling with the following (hope I got this right):

When a file is compiled, it is /not/ evaluated, except for `defmacro'
calls and `require' statements. However, if the compiled file requires
other files, those files /are/ evaluated. This means, amongst other
things, that if you compile a file which defines some variables with
`defvar' and /uses/ those variables, you will get warnings about free
variables. Those `defvar' declarations are not evaluated. The
preferred way to handle this seems to be to place all the declarations
in a separate file and then require it, forcing evaluation. (In
Viper's case, that file is viper-init.el.)

vimpulse-big.el can't do that, of course, since it's a single file. So
there's another and uglier way to force evaluation during compilation:
wrap the code in (eval-and-compile ...). Of course, you still have to
do this /before/ you actually use the variables.

(Interestingly, `defmacro' calls are evaluated regardless. This is so
the compiler can substitute the macro expansion for subsequent macro
calls. Why couldn't it make the same exception for `defvar'? According
to the Reference, section 16.6,

    [Y]ou can tell the compiler that a variable is defined using
    `defvar' with no initial value.

But it doesn't mention the need for using `eval-and-compile' in the
compiled file! Way confusing.)

So, yeah, vimpulse-big.el. If I got this right, I'll have to define
all variables at the beginning of the code, wrapped in
(eval-and-compile ...), to silence the compiler completely. Right now
it complains a lot (warnings), although it does produce the .elc.

> I don't think it makes sense to have multiple features (i.e.
> `provide' forms) in a single file (this issue was mentioned before).
> If you want to compile the single file version, shouldn't you
> instead remove all the provides except `vimpulse' (and reorder the
> code so it will work, if needed)?

If it could be automated, sure. All the makefile would have to do is
remove the last two lines of every file (one `provide' statement and
one blank line) before concatenating them. Do you think that's
possible as stated, or would one have to use awk or sed and search for
"(provide "? (I've never used awk or sed.)

Vegard 		 	   		  
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