From: Jan Dvorak <johnydog@go.cz>
To: Jamie Lokier <egcs@tantalophile.demon.co.uk>
Cc: Craig Rodrigues <rodrigc@mediaone.net>, gcc@gcc.gnu.org
Subject: Re: warning: multi-line comment (why?)
Date: Tue, 19 Sep 2000 09:05:00 -0000 [thread overview]
Message-ID: <20000919180308.A7018@napalm.go.cz> (raw)
In-Reply-To: <20000918120419.C17692@pcep-jamie.cern.ch>
On Mon, Sep 18, 2000 at 12:04:19PM +0200, Jamie Lokier wrote:
> Richard Henderson wrote:
> > > What is the point of this warning? Shouldn't the preprocessor
> > > just ignore everything between the // and the end-of-line?
> >
> > No, backslash-newline conversion happens before comments
> > are discarded. You really do have a multi-line comment;
> > one that would be dangerous if your next line weren't a
> > comment as well.
>
> But the next line _is_ a comment so the warning is inappropriate here.
>
> If this were a very unlikely situation, fair enough. But people do
> comment out multi-line macros from time to time using `//', and those
> will trigger the warning.
If you comment out macros during development, you may ignore this warning.
If you need commented macro in release, you have to comment it by /**/.
Multiline comment are dangerous, and even if next line begins with '//', it
is not the right way.
> It can't be too hard to skip whitespace and then check for `//' on the
> next line I'm sure.
I think it can be difficult. Referring to cpplex.c:
/* Skip a C++ line comment. Handles escaped newlines. Returns
non-zero if a multiline comment. The following new line, if any,
is left in buffer->read_ahead. */
static int
skip_line_comment (buffer)
cpp_buffer *buffer;
{
...
return orig_lineno != buffer->lineno;
}
so you'll need lot of readahead and lot of work to get it working right.
Jan Dvorak <johnydog@go.cz>
next prev parent reply other threads:[~2000-09-19 9:05 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-09-17 15:53 Craig Rodrigues
2000-09-17 16:12 ` Jan Dvorak
2000-09-17 16:26 ` Richard Henderson
2000-09-18 3:04 ` Jamie Lokier
2000-09-19 9:05 ` Jan Dvorak [this message]
2000-09-19 10:13 ` Jamie Lokier
2000-09-19 11:44 ` Jan Dvorak
[not found] ` <20000919214025.A30587@daikokuya.demon.co.uk>
[not found] ` <20000919214320.A30677@daikokuya.demon.co.uk>
2000-09-20 8:52 ` Jamie Lokier
2000-09-20 9:38 ` Neil Booth
2000-09-25 12:52 ` Jamie Lokier
2000-09-25 14:10 ` Neil Booth
2000-09-25 14:34 ` Joern Rennecke
[not found] ` <20000925222224.B24101@daikokuya.demon.co.uk>
[not found] ` <20000926001457.A12405@daikokuya.demon.co.uk>
2000-09-26 10:15 ` Varargs macros subtly broken Jamie Lokier
[not found] <20000925230543.A28863@daikokuya.demon.co.uk>
2000-09-25 15:18 ` warning: multi-line comment (why?) Joern Rennecke
2000-09-25 15:53 ` Neil Booth
2000-09-25 16:39 ` Joern Rennecke
2000-09-26 3:43 ` Jamie Lokier
2000-09-26 10:13 ` Neil Booth
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