preprocessor/3951: need for -MF w/ -M breaks backward compat. w/ documented features.

[cgd@broadcom.com]

The following reply was made to PR preprocessor/3951; it has been noted by GNATS.

From: cgd@broadcom.com
To: "Neil Booth" <neil@daikokuya.demon.co.uk>
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: preprocessor/3951: need for -MF w/ -M breaks backward
 compat. w/ documented features.
Date: 23 Mar 2002 15:26:26 -0800

 At Sat, 23 Mar 2002 13:16:56 +0000, Neil Booth wrote:
 > The final patch I sent you seems to be the holy grail.  It gets the
 > above right, fixes the 2.95 issues we wanted to avoid, and handles -MF,
 > -MQ and -MT like we want.  For the benefit of GNATS, I'll reproduce the
 > patch below.  If you could confirm this fixes this issue once and for
 > all, I'll apply it to all 3 trees.
 
 I just tested it with the code that tripped over the -MMD problem, and
 it seems to work fine.  I've also tested it with a bunch of additional
 code / makefiles, and i noticed nothing additional wrong.
 dependencies get built right AFAICT, etc.
 
 I can't easily go back and test it on the original problem case, but I
 don't think that's likely to break again since you now know about it.
 (You'll recall that doing that ... involved some difficulty and
 time...  if you'd like I can get the ball rolling on that again.  8-)
 
 
 chris