Question about m4 include/sinclude

Without using ifdef or something similar, is there a way to prevent m4 from

entering an infinite recursion with a file like:

% cat foo

include(`foo')

I realize I can probably do something like define a macro in the file, and then not include

the file if the macro is defined... HOWEVER, in my particular application, I cannot control all

of the m4 files... so my fear is that someone will do something like the above or even:

% setenv M4PATH "dir1:dir2"

% cat dir1/foo

include(`bar')

% cat dir2/bar

include(`foo')

And my m4 go off into an infinite loop. I can control command line options, but

when I tried --nesting-limit=1, that didn't seem to help.

About all I could think of is to have my Perl script I'm calling m4 from pre-process the

files looking for include or sinclude lines, taking into account the M4PATH environment

files, and making sure I don't repeat files (using something like stat() and the inode and

device to make sure I handle symlinks).

But this feels REALLY ugly, and if I'm going to do that, the argument from the user base

is going to be "why did you use m4... why not have your own include mechanism" (yeah,

I know).

Seems like it would be something that m4 itself should catch and (maybe optionally) puke when it finds

the same file the second time around....

Anyway, is there ANYTHING I can do to prevent multiple includes?

Thanks!

-Roger

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