Re: preprocessor/10614: -Wtrigraphs does not catch // ??/

Re: preprocessor/10614: -Wtrigraphs does not catch // ??/

[neil]

Synopsis: -Wtrigraphs does not catch // ??/

State-Changed-From-To: open->closed
State-Changed-By: neil
State-Changed-When: Sun May  4 09:05:54 2003
State-Changed-Why:
    Not a bug.  -Wcomment(s) does what you want.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10614

Re: preprocessor/10614: -Wtrigraphs does not catch // ??/

[Hallvard B Furuseth]

The following reply was made to PR preprocessor/10614; it has been noted by GNATS.

From: Hallvard B Furuseth <h.b.furuseth@usit.uio.no>
To: Neil Booth <neil@daikokuya.co.uk>
Cc: gcc-bugs@gcc.gnu.org,
    Zack Weinberg <zack@codesourcery.com>,
    gcc-gnats@gcc.gnu.org
Subject: Re: preprocessor/10614: -Wtrigraphs does not catch // ??/
Date: Sun, 4 May 2003 12:24:20 +0200

 Neil Booth writes:
 > You could persuade me that it's worthwhile warning for ??/ followed by
 > a newline in any kind of comment with -Wtrigraphs.
 
 Sounds good.  As I said in report preprocessor/10613, I think it's
 important to warn about _silent_ changes from ISO C.
 
 I suggest you also warn about ??/ <spaces/tabs> <newline>, since
 gcc ignores these spaces/tabs (with a warning).
 
 > it would warn about ??/ followed by a newline in C block comments that
 > don't change behaviour, but I don't think that would bother those who
 > want trigraph warnings off in comments.
 
 Right.  If it bothers anyone, you could add a comment in the -Wtrigraphs
 doc that ??/<newline> in comments is warned about because it _may_
 change the meaning of the program, and leave it at that.
 
 > Is that an acceptable compromise?
 
 Yes, fine.
 
 -- 
 Hallvard

Re: preprocessor/10614: -Wtrigraphs does not catch // ??/

[Neil Booth]

The following reply was made to PR preprocessor/10614; it has been noted by GNATS.

From: Neil Booth <neil@daikokuya.co.uk>
To: Hallvard B Furuseth <h.b.furuseth@usit.uio.no>
Cc: gcc-bugs@gcc.gnu.org, Zack Weinberg <zack@codesourcery.com>,
	gcc-gnats@gcc.gnu.org
Subject: Re: preprocessor/10614: -Wtrigraphs does not catch // ??/
Date: Sun, 4 May 2003 10:52:12 +0100

 Hallvard B Furuseth wrote:-
 
 > neil@gcc.gnu.org writes:
 > >     Not a bug.  -Wcomment(s) does what you want.
 > 
 > Sorry, no.  What I want is for -Wtrigraphs to warn about code that will
 > compile differently with and without trigraph support.  However,
 
 Ah, I see.
 
 That is quite a strict condition, and not one I'm willing to implement
 because of the cost and ugliness of the checks in C comments.
 For example, we turn off -Wtrigraphs in comments because that is what
 many people have requested, but IMO adding a lot of code to warn that
 an instance of ??/\n, or multiple thereof, that happen to be preceded by
 '*' and followed by '/' and would therefore terminate a C block comment
 is unreasonable, but does lead to differing behaviour with and without
 -trigraphs.
 
 > - The warning from gcc -trigraphs -Wcomments gives no indication of
 >   this; it could come from a `//..\' line.
 > 
 > - The warning is only given when -trigraphs or -std=c99 is given.
 >   So if I just compile with 'gcc -Wcomments', I'll get no clue that the
 >   program will silently compile differently on an ISO C compiler.
 
 You could persuade me that it's worthwhile warning for ??/ followed by
 a newline in any kind of comment with -Wtrigraphs.  This would be
 fairly simple to implement, and would mean that -Wtrigraphs warns about
 all program-changing behaviour.  In addition, it would warn about ??/
 followed by a newline in C block comments that don't change behaviour,
 but I don't think that would bother those who want trigraph warnings
 off in comments.
 
 Is that an acceptable compromise?
 
 Neil.

Re: preprocessor/10614: -Wtrigraphs does not catch // ??/

[Hallvard B Furuseth]

The following reply was made to PR preprocessor/10614; it has been noted by GNATS.

From: Hallvard B Furuseth <h.b.furuseth@usit.uio.no>
To: neil@gcc.gnu.org,
    gcc-bugs@gcc.gnu.org,
    gcc-prs@gcc.gnu.org,
    nobody@gcc.gnu.org,
    gcc-gnats@gcc.gnu.org
Cc:  
Subject: Re: preprocessor/10614: -Wtrigraphs does not catch // ??/
Date: Sun, 4 May 2003 11:20:12 +0200

 neil@gcc.gnu.org writes:
 >     Not a bug.  -Wcomment(s) does what you want.
 
 Sorry, no.  What I want is for -Wtrigraphs to warn about code that will
 compile differently with and without trigraph support.  However,
 
 - The warning from gcc -trigraphs -Wcomments gives no indication of
   this; it could come from a `//..\' line.
 
 - The warning is only given when -trigraphs or -std=c99 is given.
   So if I just compile with 'gcc -Wcomments', I'll get no clue that the
   program will silently compile differently on an ISO C compiler.
 
 -- 
 Hallvard

preprocessor/10614: -Wtrigraphs does not catch // ??/

[Hallvard B Furuseth]

>Number:         10614
>Category:       preprocessor
>Synopsis:       -Wtrigraphs does not catch // ??/
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat May 03 23:36:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     Hallvard B Furuseth
>Release:        3.2.3
>Organization:
University of Oslo
>Environment:
System: SunOS bombur.uio.no 5.8 Generic_108528-13 sun4u sparc SUNW,Ultra-5_10
Architecture: sun4

	
host: sparc-sun-solaris2.8
build: sparc-sun-solaris2.8
target: sparc-sun-solaris2.8
configured with: ../gcc-3.2.3/configure --enable-languages=c,c++,f77 --disable-shared --disable-multilib --prefix=/usit/bombur/hbf --enable-version-specific-runtime-libs --enable-threads
>Description:
	-Wtrigraphs should warn about `//' comment lines that end with
	`??/', since -trigraphs changes whether or not the next line is
	taken to be part of the comment.

	Also, when that is fixed, the the description of -Wtrigraphs
	should mention this exception to the statement that trigraphs in
	comments are not warned about.
>How-To-Repeat:
	bash$ cat a.c
	#include <stdio.h>
	int main()
	{
	    // multi-line comment ??/
	    puts("oops");
	    return 0;
	}
	bash$ gcc -trigraphs -Wtrigraphs a.c
	bash$ ./a.out
	bash$
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted: