[Bug c++/15519] New: preprocessor mistreats backslash-blank-newline in // comment

[Bug c++/15519] New: preprocessor mistreats backslash-blank-newline in // comment

[doug at cs dot dartmouth dot edu]

In both 3.3.1 (cygwin, NT) and 3.2.2 (redhat, linux) the preprocessor
silently--and wrongly--eats the declaration below, where $ marks
have been placed to show the end of lines.  The comment was carefully
written to avoid the very misbehavior that it elicited.
To exhibit the trouble, remove the $ marks and compile with
g++ -pedantic -E

// boolean operation /\ $
extern int band(int,int);$

In some contexts g++ warns of the presence of backslash-space-newline,
but not in comments.  Under option -Wall, it reports a "multiline
comment".  The warnings do not, however, point out that the g++
interpretation is nonstandard, even in -pedantic mode.

-- 
           Summary: preprocessor mistreats backslash-blank-newline in //
                    comment
           Product: gcc
           Version: 3.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: doug at cs dot dartmouth dot edu
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: I can't guess what a "triplet" is


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15519

[Bug preprocessor/15519] preprocessor mistreats backslash-blank-newline in // comment

[bangerth at dealii dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c++                         |preprocessor


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15519

[Bug c++/15519] preprocessor mistreats backslash-blank-newline in // comment

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-05-18 15:39 -------
I cannot reproduce this with released versions of 3.2.2, 3.2.3, 3.3.3, or 3.4.0 (or the mainline of gcc).

Are you sure that you can reproduce it with the given example.

I get for 3.3.x and below:
pr15519.cc:3: syntax error at end of input
For 3.4.0 and above:
pr15519.cc:2: error: expected constructor, destructor, or type conversion at end of input
pr15519.cc:2: error: expected `,' or `;' at end of input

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
          Component|preprocessor                |c++


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15519

[Bug c++/15519] preprocessor mistreats backslash-blank-newline in // comment

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-05-18 15:42 -------
Woops I missed the sentence that says "remove the $ marks".

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15519

[Bug c++/15519] preprocessor mistreats backslash-blank-newline in // comment

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2004-05-18 15:42:43
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15519

[Bug preprocessor/15519] preprocessor mistreats backslash-blank-newline in // comment

[zack at codesourcery dot com]

------- Additional Comments From zack at codesourcery dot com  2004-05-18 16:17 -------
Subject: Re:  New: preprocessor mistreats
 backslash-blank-newline in // comment

"doug at cs dot dartmouth dot edu" <gcc-bugzilla@gcc.gnu.org> writes:

> // boolean operation /\ $
> extern int band(int,int);$
>
> In some contexts g++ warns of the presence of backslash-space-newline,
> but not in comments.  Under option -Wall, it reports a "multiline
> comment".  The warnings do not, however, point out that the g++
> interpretation is nonstandard, even in -pedantic mode.

That's because it isn't nonstandard.  It's the mapping of "end-of-line
indicators" in translation phase 1 (C99 5.1.1.2) -

   Physical source file multibyte characters are mapped, in an
   implementation-defined manner, to the source character set
   (introducing new-line characters for end-of-line indicators)

The term "end-of-line indicator" is defined in section 5.2.1 as "In
source files, there shall be some way of indicating the end of each
line of text" - i.e. it's implementation-defined.  GCC's definition of
an end-of-line indicator is "any number of horizontal whitespace
characters (space \t \v \f) followed by \n, \r\n, or \r".

Identical text to C99 5.1.1.2 appears in C++98 section 2.1
[lex.phases] - there doesn't seem to be a definition of "end-of-line
indicator" at all.

---

So, no, we're not going to make -pedantic care about this.  However, a
patch to make the backslash-space-newline warning trigger within
comments when it will change the meaning of the program (and ONLY
then) would be welcome.  Alternatively, the "multiline comment"
warning could be turned on by default.

zw


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15519

[Bug preprocessor/15519] preprocessor mistreats backslash-blank-newline in // comment

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-09-08 17:28 -------
See 8270.

*** This bug has been marked as a duplicate of 8270 ***

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |DUPLICATE


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15519