preprocessor/2706: #defines expanded when -fpreprocessed given

[Zack Weinberg]

The following reply was made to PR preprocessor/2706; it has been noted by GNATS.

From: "Zack Weinberg" <zackw@Stanford.EDU>
To: Nathan Sidwell <nathan@codesourcery.com>
Cc: Neil Booth <neil@daikokuya.demon.co.uk>, gcc-gnats@gcc.gnu.org
Subject: Re: preprocessor/2706: #defines expanded when -fpreprocessed given
Date: Wed, 2 May 2001 17:00:33 -0700

 On Wed, May 02, 2001 at 05:00:15PM +0100, Nathan Sidwell wrote:
 > 
 > > It might be better to emit a diagnostic from cpplib, along the lines
 > > of "'#define' not honored in already-preprocessed source", and discard
 > > the pseudo-directive.  The diagnostics we give right now are rather
 > > unhelpful.  Thoughts?
 > That was the kind of error I expected. What triggered this was cc1plus
 > silently swallowing a #include.
 
 I looked into providing this.  In order for you to get the nice error
 both with and without -save-temps, it needs to come from c-lex.c.
 Unfortunately, cpplib does not export enough information to do this
 reliably.  I need to know when a token is the first one on a line, and
 I need to be able to discard a line, both from the context of cpplib's
 user.  cpplib throws away the information about tokens being first on
 a line deep inside its inner loop.  The routine to skip the rest of a
 line is private; if I simply export it it doesn't work properly
 (caller gets an EOF as the next token processed).
 
 I propose we live with the unfriendly error messages for now, until
 cpplib can be adjusted to give c-lex what it needs.  I'm testing a
 slightly-revised patch right now on the 3.0 branch.
 
 zw