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From: guy%gorodish@Sun.COM (Guy Harris)
Newsgroups: comp.unix.wizards,comp.unix.questions
Subject: Re: need cpp macros to concatenate names
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Date: Mon, 4-May-87 19:12:39 EDT
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Posted: Mon May  4 19:12:39 1987
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> The above works on some preprocessors, not others.

Yup.  Somewhere between System III and System V, I think, the
preprocessor was changed to turn escaped newlines, in the case you
mention, into blanks.  This is, in fact, incorrect, as I read the
ANSI C draft of October 1, 1986, since escaped newlines are to be
thrown out fairly early in the processing of the source code.

> In all cases, the escaped new line provides token separation.

Which is also incorrect, as I read the ANSI C draft.

> Our intent is to be portable to any System V machine with a minimum of
> changes.
> 
> Anybody have a suggestion? (We know about m4 and sed, but we can't afford to
> add another step to the compilation of many thousands of lines of code, which
> are all compiled together on a major build of an executable module.)

If you really intend to be portable to any conceivable S5-compatible
implementation, I suggest you use "m4" and/or "sed", since there's no
*documented* way of gluing tokens together in pre-ANSI C.

The following trick works on the versions of the "Reiser" preprocessor
that are distributed with AT&T UNIX releases, but somebody may have
changed things so as to make it not work (unlikely - I know of nobody
who has - but not impossible):

	#define concat(x,y) x/**/y

Note, BTW, that you MUST NOT call "concat" as

	concat(foo, bar)

and expect it to glue "foo" and "bar" together - it will glue "foo"
and " bar" (note the blank) together.