preprocessor/7029: preprocessor should ignore #warning with -M

[Zack Weinberg]

The following reply was made to PR preprocessor/7029; it has been noted by GNATS.

From: Zack Weinberg <zack@codesourcery.com>
To: Neil Booth <neil@daikokuya.co.uk>
Cc: wolfgang.bangerth@iwr.uni-heidelberg.de, gcc-gnats@gcc.gnu.org,
	gcc-bugs@gcc.gnu.org
Subject: Re: preprocessor/7029: preprocessor should ignore #warning with -M
Date: Mon, 1 Jul 2002 14:20:38 -0700

 On Mon, Jul 01, 2002 at 10:04:49PM +0100, Neil Booth wrote:
 > > IMHO, warnings generated by #warning may be omitted when not
 > > actually compiling code, for example when using -M to
 > > generate dependency lists. They seem inappropriate for this
 > > task.
 > > >How-To-Repeat:
 > > program> echo "#warning Warn about something" > x.cc
 > > program> gcc -M x.cc 
 > > x.cc:1:2: warning: #warning Warn about something
 > > x.o: x.cc
 > 
 > Warnings are sent to stderr and the dpendency information isn't; so if
 > you don't want the warnings you are free to pipe stderr to /dev/null.
 > If you still wanted to retain errors but not warnings you can use -w,
 > or check the compiler return code.
 > 
 > So I disagree that there is any reason to change the existing behaviour,
 > and want to close this PR.  Do you agree, Zack?
 
 Well, I think it might be reasonable for -M switches that inhibit
 compilation to imply -w.  Presumably the user will get all the
 warnings in due course as part of the real compilation.
 
 zw