Newsgroups: comp.lang.c
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: Nesting of a preprocessor directive within a macro defn
Message-ID: <1990Sep2.022039.3691@zoo.toronto.edu>
Organization: U of Toronto Zoology
References: <849@gtenmc.UUCP>
Date: Sun, 2 Sep 90 02:20:39 GMT

In article <849@gtenmc.UUCP> ravim@gtenmc.UUCP (Ravi Kumar Mandava) writes:
>Is nesting of a preprocessor directive within a macro definition (RHS) not
>allowed?

It is not possible.  The very first thing that happens to ANSI C source
during compilation is that backslashed newlines are stripped out, so any
"#" within the RHS is no longer at the start of a line and hence does
not begin a preprocessor directive.

(And incidentally, the result of macro expansion "is not processed as a
preprocessing directive even if it resembles one", section 3.8.3.4.)

Some old C compilers may have permitted such things, due to the vagueness
of the old definition of how the preprocessor features interacted.
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