bug? instruction not compiled below comment

[walter]

I wrote a program, and found one line of source code
not compiled out. I rewrote it for simplicity as below.
The comment in the program is big5 code text.

--- my program ---
main(){
int i, a[8];
for (i=0;i<3;i++) a[i]=0;
// ÁקK³Q·j´M¦¨¥\
a[3]=-1;

for (i=0;i<4;i++)
printf("%d ",a[i]);
}
--- end of my program ---

The output is not "0 0 0 -1" because the comment is ended
with "\", and this makes a[3]=-1 to be regarded as comment.

I wonder this is a bug or not?

[Robert Stankowic]

"walter" <kg**@pchome.co m.tw> schrieb im Newsbeitrag
news:bp******** @netnews.hinet. net...

I wrote a program, and found one line of source code
not compiled out. I rewrote it for simplicity as below.
The comment in the program is big5 code text.

--- my program ---
main(){
int i, a[8];
for (i=0;i<3;i++) a[i]=0;
// ÁקK³Q·j´M¦¨¥\
a[3]=-1;

for (i=0;i<4;i++)
printf("%d ",a[i]);
}
--- end of my program ---

The output is not "0 0 0 -1" because the comment is ended
with "\", and this makes a[3]=-1 to be regarded as comment.

I wonder this is a bug or not?

No bug. the '\' at the end "escapes" the newline and therefore the comment
does not end here
Robert

[Irrwahn Grausewitz]

walter <kg**@pchome.co m.tw> wrote:

I wrote a program, and found one line of source code
not compiled out. I rewrote it for simplicity as below.
The comment in the program is big5 code text.

--- my program --- #include <stdio.h> main(){ int main( void ){ int i, a[8];
for (i=0;i<3;i++) a[i]=0;
// ÁקK³Q·j´M¦¨¥\
a[3]=-1;

for (i=0;i<4;i++)
printf("%d ",a[i]); return 0; }
--- end of my program ---

The output is not "0 0 0 -1" because the comment is ended
with "\", and this makes a[3]=-1 to be regarded as comment.

I wonder this is a bug or not?

Per definition in the standard, the C preprocessor is required to
delete any backslash immediately followed by a new-line character,
thus "splicing physical source lines to form logical source lines".
This splicing happens prior to tokenization and comment elimination.

Therefore I consider the above construct to be a flaw in your code.

FWIW, the compiler I use emits a "warning: multi-line comment"
diagnostic.

HTH
Regards
--
Irrwahn
(ir*******@free net.de)

[Kevin Bracey]

In message <bp********@net news.hinet.net>
walter <kg**@pchome.co m.tw> wrote:

--- my program ---
main(){
int i, a[8];
for (i=0;i<3;i++) a[i]=0;
// ÁקK³Q·j´M¦¨¥\
a[3]=-1;

for (i=0;i<4;i++)
printf("%d ",a[i]);
}
--- end of my program ---

The output is not "0 0 0 -1" because the comment is ended
with "\", and this makes a[3]=-1 to be regarded as comment.

I wonder this is a bug or not?

I suspect your compiler isn't specified as handling Big5 source files. Big5
is not a terribly good encoding method, for exactly this reason - standard
ASCII-type tools are liable to misinterpret it. You're likely to have even
worse problems in string literals.

--
Kevin Bracey, Principal Software Engineer
Tematic Ltd Tel: [phone]
182-190 Newmarket Road Fax: [phone]
Cambridge, CB5 8HE, United Kingdom WWW: http://www.tematic.com/

[Simon Biber]

"walter" <kg**@pchome.co m.tw> wrote:

I wrote a program, and found one line of source code
not compiled out. I rewrote it for simplicity as below.
The comment in the program is big5 code text.
I recommend you use UTF-8 code instead, as it does not
suffer from this problem. All non-ASCII characters are
encoded using only characters with values outside the
ASCII set, so there are no surprises with backslashes
or any other characters.

So, instead of writing: // ÁקK³Q·j´M¦¨¥\
write: // ��被�尋 �功
I wonder this is a bug or not?

If your compiler specifies that it takes BIG5-encoded text
as input, then this is a bug. If the compiler specifies that
it takes ASCII or any ISO-8859 encoded text, then it is not
a bug, because there really is a backslash as the final
character in the line.

--
Simon.

[walter]

Irrwahn Grausewitz:

walter <kg**@pchome.co m.tw> wrote:

....

The output is not "0 0 0 -1" because the comment is ended
with "\", and this makes a[3]=-1 to be regarded as comment.

I wonder this is a bug or not?

Per definition in the standard, the C preprocessor is required to
delete any backslash immediately followed by a new-line character,
thus "splicing physical source lines to form logical source lines".
This splicing happens prior to tokenization and comment elimination.

Therefore I consider the above construct to be a flaw in your code.

FWIW, the compiler I use emits a "warning: multi-line comment"
diagnostic.

HTH
Regards

I found a compile option -Wcomment, which could generate
"warning: multi-line comment" message. I've add this
option to my makefile. Thanks for your information.

Regards,

[Irrwahn Grausewitz]

walter <kg**@pchome.co m.tw> wrote:

Irrwahn Grausewitz:

<snip>

FWIW, the compiler I use emits a "warning: multi-line comment"
diagnostic.

I found a compile option -Wcomment, which could generate
"warning: multi-line comment" message. I've add this
option to my makefile. Thanks for your information.

<OT>
If you're using gcc you should include "-W -Wall" in the command line.
(No, -Wall on itself doesn't turn on all [generally useful] warnings.)
</OT>

Regards
--
Irrwahn
(ir*******@free net.de)

[CBFalconer]

walter wrote:

I wrote a program, and found one line of source code
not compiled out. I rewrote it for simplicity as below.
The comment in the program is big5 code text.

--- my program ---
main(){
int i, a[8];
for (i=0;i<3;i++) a[i]=0;
// ÁקK³Q·j´M¦¨¥\
a[3]=-1;

for (i=0;i<4;i++)
printf("%d ",a[i]);
}
--- end of my program ---

The output is not "0 0 0 -1" because the comment is ended
with "\", and this makes a[3]=-1 to be regarded as comment.

I wonder this is a bug or not?

If you don't have a C99 compliant compiler, the line beginning
with // is a syntax error in the first place. C90 comments are
enclosed in /* ... */.

If you do have a C99 compiler (doubtful), the terminal '\' is
documented as splicing lines together, so that the "a[3]..." is
part of the comment line.

If you are using something with non-standard extensions, it is up
to you to understand what they are doing. c.l.c cannot help you,
simply because they are non-standard, undocumented (to us), and we
just don't understand them. Such questions are off-topic here.

--
Chuck F (cb********@yah oo.com) (cb********@wor ldnet.att.net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net> USE worldnet address!

[Dan Pop]

In <33************ *************** *****@4ax.com> Irrwahn Grausewitz <ir*******@free net.de> writes:

<OT>
If you're using gcc you should include "-W -Wall" in the command line.
(No, -Wall on itself doesn't turn on all [generally useful] warnings.)
</OT>

-Wall on itself doesn't turn on all generally useful warnings, but the
right companion option for achieving this purpose is -O, not -W.

The warnings generated by -W have been excluded from -Wall precisely
because far too many people don't consider them as being generally useful.
IMHO, they're more like a source of compiler noise: far too much *correct*
C code triggers them.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de

[CBFalconer]

Irrwahn Grausewitz wrote:

walter <kg**@pchome.co m.tw> wrote:

Irrwahn Grausewitz:

<snip>

FWIW, the compiler I use emits a "warning: multi-line comment"
diagnostic.

I found a compile option -Wcomment, which could generate
"warning: multi-line comment" message. I've add this
option to my makefile. Thanks for your information.

<OT>
If you're using gcc you should include "-W -Wall" in the command line.
(No, -Wall on itself doesn't turn on all [generally useful] warnings.)
</OT>

I routinely include -W -Wall -ansi -pedantic -Wwrite-strings. I
do this by running gcc through an alias (which is bypassed in make
files). I very rarely need to use any less restrictive options.

--
Chuck F (cb********@yah oo.com) (cb********@wor ldnet.att.net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net> USE worldnet address!