dev-cpp-users

RE: [Dev-C++] Dev-C++ Bug? Using backslash within comments

[Reid T. <Rei...@at...>]

Jonathan Dearborn wrote:
> Here's an example program, though if you'd like to see the
> compiled program
> I found it on, check out
> http://www.maybe-phil.net/websites/no-skill/jnrdev/en/jnrdev3/
>=20
> That program is based on SDL, so if you're not into that,
> just use this one:
> -----------------
>=20
> #include <stdio.h>
> #include <iostream>
>=20
> int main(int argc, char *argv[])
> {
>   int y;
>   int x =3D 200;
>   //  let's cause a problem with backslash \
>   y =3D  x*55;
>   printf("%d\n",y);
>   system("PAUSE");
>=20
>   printf("\n");
>=20
>   //  now without it
>   y =3D  x*55;
>   printf("%d\n",y);
>   system("PAUSE");
>   return 0;
>=20
>   //  shouldn't the compiler ignore everything after these C++ style
> comments? }
>=20
>=20
> ------------------
> That about shows it.  I know it's a little bother and I'm not
> surprised it hasn't come up before, but I just wanted to help in case
> someone else gets
> stuck.  Of course, it's only a problem with the C++ style comments.

well, you just escaped the line ending character, basically telling the
compiler suite that the comment line has not ended.  The compiler will
end the comment when it sees a valid line end.

reid

RE: [Dev-C++] Dev-C++ Bug? Using backslash within comments

[Reid T. <Rei...@at...>]

Jonathan Dearborn wrote:
> Reid, you're definitely right about escaping the line-break. That's
> the problem, but is that a feature of the compiler (as Peter said) or
> is it a little mistake in the compiler source?  As I said before,
> other compilers ignore the backslash if it's in a comment (as I
> believe they should).  Also, if it's a feature, shouldn't it be
> useful?  There is a separate comment style (the old style /*text*/)
> in case you want to comment multiple lines. Escape characters
> shouldn't affect comments.  I think this is just a bug.  A small bug,
> but how should it be handled?=20
>=20
> Verne, are you saying your compiler gave a warning because there's
> code after the main() return?  That's fine, it's just a comment. I
> would expect that.  I use Dev-C++ exclusively for editing and
> compiling, by the way.=20
>=20
> _________________________________________________________________
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SOLARIS SUN compiler
$ CC -V
CC: Sun C++ 5.5 2003/03/12
$ CC test.C
does not ignore it

"test.C", line 11: Warning: The variable y has not yet been assigned a
value.
1 Warning(s) detected.
NOTE:  The other compilers may very well output a similar warning IF you
pass the proper flags.
  EXAMPLE:  cygwin compiler called 'g++ -Wall' declares=20
            $ g++ -Wall test.cpp
              test.cpp:9:5: warning: multi-line comment

SOLARIS gcc
$ g++ -v
Reading specs from
/usr/local/lib/gcc-lib/sparc-sun-solaris2.6/2.95.2/specs
gcc version 2.95.2 19991024 (release)

does not ignore it

AIX
$ cc -v
exec: /usr/bin/pg(/usr/bin/pg,/usr/lib/nls/msg/en_US/vacpp.help,NULL)=20
  VisualAge C++ Professional / C for AIX Compiler, Version 6

does not ignore it

CYGWIN
$ g++ -v
Reading specs from /usr/lib/gcc/i686-pc-cygwin/3.4.4/specs
Configured with: /gcc/gcc-3.4.4/gcc-3.4.4-1/configure --verbose
--prefix=3D/usr --exec-prefix=3D/usr --sysconfdir=3D/etc =
--libdir=3D/usr/lib
--libexecdir=3D/usr/lib --mandir=3D/usr/share/man =
--infodir=3D/usr/share/info
--enable-languages=3Dc,ada,c++,d,f77,java,objc --enable-nls
--without-included-gettext --enable-version-specific-runtime-libs
--without-x --enable-libgcj --disable-java-awt --with-system-zlib
--enable-interpreter --disable-libgcj-debug --enable-threads=3Dposix
--enable-java-gc=3Dboehm --disable-win32-registry =
--enable-sjlj-exceptions
--enable-hash-synchronization --enable-libstdcxx-debug : (reconfigured)=20
Thread model: posix
gcc version 3.4.4 (cygming special) (gdc 0.12, using dmd 0.125)

does not ignore it

So, based on empirical evidence, no, prob not a bug.

reid

RE: [Dev-C++] Dev-C++ Bug? Using backslash within comments

[Reid T. <Rei...@at...>]

Reid Thompson wrote:
> Jonathan Dearborn wrote:
a question, what are the 'other' compiler you mention?


reid

RE: [Dev-C++] Dev-C++ Bug? Using backslash within comments

[Reid T. <Rei...@at...>]

Reid Thompson wrote:

one more that I remembered that I had... also ignores it...

C:\>cl /?
Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 13.10.3077 for
80x86 Copyright (C) Microsoft Corporation 1984-2002. All rights
reserved.

...
c:\test.cpp(11) : warning C4700: local variable 'y' used without having
been ini tialized Microsoft (R) Incremental Linker Version 7.10.3077
Copyright (C) Microsoft Corporation.  All rights reserved.

/out:test.exe
test.obj

C:\>test.exe
29721173
Press any key to continue . . .

11000
Press any key to continue . . .

reid

RE: [Dev-C++] Dev-C++ Bug? Using backslash within comments

[Jonathan D. <gri...@ho...>]

Well, Reid, that sounds like good enough evidence.  I'm not positive on what 
the "other" compiler is, but I think it is Visual C++.  At any rate, thanks 
for clearing that up.  In my opinion, it shouldn't be read by the compiler 
because the preprocessor should take out all commented text.  Maybe I've 
just never heard of extending a one-line comment and this is how it's done.  
I didn't want Dev-C++ to be the odd one out if more compilers ignored it 
(since I only use Dev-C++).  I now doubt that it'll ever be a big enough 
problem unless this rarely-used feature to overlook backslashes at the end 
of comments in a (most likely) single compiler is used in popular free 
source.  I don't see that happening more than where I got it from.  Thanks 
for your help, Reid.

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Re: [Dev-C++] Dev-C++ Bug? Using backslash within comments

[Peter B. <pb...@hg...>]

Jonathan Dearborn wrote:
(...)
> this is how it's done.  I didn't want Dev-C++ to be the odd one out if 
> more compilers ignored it (since I only use Dev-C++).  I now doubt that 
(...)

BTW, not Dev-C++ is the compiler it's gcc which is called by Dev-C++ to 
do the compilation. So the problem should not be addressed to the 
Dev-C++ but to the gcc developers.

Peter

RE: [Dev-C++] Dev-C++ Bug? Using backslash within comments

[Reid T. <Rei...@at...>]

Jonathan Dearborn wrote:
> Well, Reid, that sounds like good enough evidence.  I'm not positive
> on what the "other" compiler is, but I think it is Visual C++.  At
> any rate, thanks for clearing that up.
 =20
> In my opinion, it shouldn't
> be read by the compiler because the preprocessor should take out all
> commented text.=20

That is what is happening, the line following the 'intended' comment
line with the terminating '\' is considered as part of the 'intended'
comment and is being handled as such ( i.e. it is not converted to
executable form by the compiler -- whether that means that it is not
passed to the compiler, or is passed but is ignored by the compiler
'because it's a comment' I don't know.)

>Maybe I've just never heard of extending a one-line
> comment and this is how it's done. I didn't want Dev-C++ to be the
> odd one out if more compilers ignored it (since I only use Dev-C++).=20
> I now doubt that it'll ever be a big enough problem unless this
> rarely-used feature to overlook backslashes at the end of comments in
> a (most likely) single compiler is used in popular free source.  I
> don't see that happening more than where I got it from.  Thanks for
> your help, Reid.=20
>=20
> _________________________________________________________________
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reid

RE: [Dev-C++] Dev-C++ Bug? Using backslash within comments

[Jonathan D. <gri...@ho...>]

Reid, you're definitely right about escaping the line-break.  That's the 
problem, but is that a feature of the compiler (as Peter said) or is it a 
little mistake in the compiler source?  As I said before, other compilers 
ignore the backslash if it's in a comment (as I believe they should).  Also, 
if it's a feature, shouldn't it be useful?  There is a separate comment 
style (the old style /*text*/) in case you want to comment multiple lines.  
Escape characters shouldn't affect comments.  I think this is just a bug.  A 
small bug, but how should it be handled?

Verne, are you saying your compiler gave a warning because there's code 
after the main() return?  That's fine, it's just a comment.  I would expect 
that.  I use Dev-C++ exclusively for editing and compiling, by the way.

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