Re: Maintaining global state with m4 macros

[Paolo Amoroso]

Thanks Grant, here's some context on what I'm working on and what I tried.

I'm using m4 as the macro processor of an Intel 8080 cross-assembler
I'm developing in Python
(nothing fancy, I'm a hobbyist). I'd like to write macros for
generating unique Assembly labels that
would be good approximations of local labels.

An approach is to generate the labels from the unique values of a
global counter, hence my question.
I'm thinking of something like:

    define(`nextlabel', `L'nextcount)

    nextlabel:
            mvi a, 3

My initial attempt was like this:

    define(`COUNTER', `0')

    define(`newlabel', ``$1'incr(COUNTER)')

But this is ineffective as no global COUNTER can be referenced. Then I
tried this:

    define(`newlabel', pushdef(`COUNTER', `incr(COUNTER)')`$1'COUNTER)

which generates an infinite loop. Another approach I tried is to fetch
a unique integer from outside
of m4 via esyscmd:

    define(`newlabel', `$1'esyscmd(`date +"%s"|tr -d "\n"'))

This aborts m4 with an internal error and %s isn't granular enough
anyway. A variation on esyscmd
I experimented with is:

    define(`newlabel',`$1'esyscmd(`echo $RANDOM|tr -d "\n"'))

Which returns an empty string.


Paolo