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In article <1829@ns-mx.uiowa.edu> cmdglv@vaxa.weeg.uiowa.edu writes:
>      Here's a fun little bug that I just discovered in Microsoft C V6.0.
>             printf("Question marks: '??'");
>      I get the following output:
                      Question marks: '^

Aaahh! but not a bug, I'm afraid...
Note on page 424 of TFM (MSC Advanced Programming Techniques manual),
in the section B.1.7 titled Trigraphs, it is mentioned that the character
sequence ??' translates into the circumflex character.  This is included 
in the ANSI standard for Trigraph sequences.  Sorry, but you'll have to
change your program.

Note:  one way to do this is to use the string concatenation feature, as in:
       printf ("Question marks: '?" "?'");

In article <1829@ns-mx.uiowa.edu> cmdglv@vaxa.weeg.uiowa.edu writes:

>      Here's a fun little bug that I just discovered in Microsoft C V6.0.
>                          printf("Question marks: '??'");
>I get the following output:
>                       Question marks: '^

>     It's not quite what I expected.  And it breaks a whole series of 
>programs I have that use quoted question marks within strings :(

This is not a bug. ANSI C defines a thing called trigraphs for machines or
terminals that don't have some of the less common characters. 
Trigraphs are three character macro like devices that allow you to make
funny characters.  Ex.  ??= is #   ??( is [  ??! is |   and  ??' is ^ .
There are others.

6.0 is trys to be ANSI in every way it can.  Another difference between
5.1 and 6.0 that has given me compiler errors is the fact that the type
of a shift expression now is the same type as the left side of the expression:
(short_v << long_v) is of type short, in 5.1 it would have been a long.

You can still put your ??' in a printf, just type \?\?' or ?\?' .

Brynn

On 11 Jul 90 14:31:09 GMT,
cmdglv@vaxa.weeg.uiowa.edu (Mark Gleaves) said:
>                           printf("Question marks: '??'");
> I get the following output:

>                        Question marks: '^

Way to Microsoft. I thought trigraphs were bad, now we have digraphs too.



--

Frank Kolakowski 

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In article <1829@ns-mx.uiowa.edu>, I wrote...
> 
>      Here's a fun little bug that I just discovered in Microsoft C V6.0.
>When I run the following:
> 
>                          printf("Question marks: '??'");
> 
>I get the following output:
> 
>                       Question marks: '^
> 
>     It's not quite what I expected.

Thanks to all of you who pointed out that ??' is a valid trigraph under the
ANSI C standard.  I just wish I would have known that before I wrote all
those programs using MSC 5.1.  Live and learn...

*******************************************************************************
Mark Gleaves                              Phone:  (319)335-9780
Center for Health Effects of              Fax:  (319)335-9200
   Environmental Contamination            Internet:  cmdglv@vaxa.weeg.uiowa.edu
SHRI, S-112 Westlawn                      Bitnet:  cmdglvva@uiamvs.bitnet
University of Iowa
Iowa City, IA  52246                      "Hurrah, boys, we've got them!"
USA                                          - George A. Custer, June 25, 1876.
*******************************************************************************

In article <1829@ns-mx.uiowa.edu> cmdglv@vaxa.weeg.uiowa.edu writes:
>
>      Here's a fun little bug that I just discovered in Microsoft C V6.0.
>When I run the following program:
>
>                       #include <stdio.h>
>                       void main() {
>                          printf("Question marks: '??'");
>                       }
>
>I get the following output:
>
>                       Question marks: '^
>
>     It's not quite what I expected.  And it breaks a whole series of 
>programs I have that use quoted question marks within strings :(
>
>P.S., Does anybody else out there resent being patronized, belittled, and
>disbelieved when they try to report a bug to Microsoft Technical Support?
>

MS Tech support probably receives much more than its share of "bug" reports.
What you have stumbled upon is not a bug, it is a feature.  Since not
all terminals (outside of the UNIX/C/DEC,SUN,AT&T world) can do all of
the characters required by C, the ANSI standard provides a method for
specifying certain characters by sequences known as trigraphs.  All
trigraphs begin with a ??.  The trigraph for ^ is (yes, you guessed it)
??'.  See A12.1 of K&R 2nd Ed. 

Neil



=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Neil I.  Weisenfeld                    | InterNet: weisen@eniac.seas.upenn.edu
Dept. of Computer and Info. Sciences   | USPS: I dunno, I'm moving...
University of Pennsylvania             | PENNmail: Don't even try it...
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In article <1990Jul11.175340.12779@granite.cr.bull.com> buck@granite.cr.bull.com (Kenneth J. Buck) writes:
>In article <1829@ns-mx.uiowa.edu> cmdglv@vaxa.weeg.uiowa.edu writes:
>>      Here's a fun little bug that I just discovered in Microsoft C V6.0.
>>             printf("Question marks: '??'");
>>      I get the following output:
>                      Question marks: '^
>
>Aaahh! but not a bug, I'm afraid...
>Note on page 424 of TFM (MSC Advanced Programming Techniques manual),
>in the section B.1.7 titled Trigraphs, it is mentioned that the character
>sequence ??' translates into the circumflex character.  This is included 
>in the ANSI standard for Trigraph sequences.  Sorry, but you'll have to
>change your program.
>
>Note:  one way to do this is to use the string concatenation feature, as in:
>       printf ("Question marks: '?" "?'");


The more approved way in 'C' is to use the '\' escape character to force the
character you want. ie

printf ("Question marks: '\?\?'");


Russ Poffenberger               DOMAIN: poffen@sj.ate.slb.com
Schlumberger Technologies       UUCP:   {uunet,decwrl,amdahl}!sjsca4!poffen
1601 Technology Drive		CIS:	72401,276
San Jose, Ca. 95110             (408)437-5254

cmdglv@vaxa.weeg.uiowa.edu (Mark Gleaves) writes:
>      Here's a fun little bug that I just discovered in Microsoft C V6.0.
>When I run the following program:
>                       #include <stdio.h>
>                       void main() {
>                          printf("Question marks: '??'");
>                       }
>I get the following output:
>                       Question marks: '^

It's not a Microsoft bug!  ANSI C defines 9 sequences of "trigraphs"
(sequences of 3 characters) which are translated into single characters
as the very first stage of program interpretation.  These nine
trigraphs provide support for characters required by the C language
but not available in all character sets.

All trigraph sequences begin with two question marks.  If in a program,
two question marks are not followed by one of the nine specified
charcters, the two question marks are left unchanged.

By luck, you picked one of the trigraphs in your example.  The sequence
??' is converted to ^.  Since the whole thing is enclosed in double
quotes, the resulting unmatched single quote is not an error (just wrong).

To produce precisely the output you wish, just escape the second single
quote:
	printf("Question marks: '??\'");

It is documented in the ANSI C standard Rationale as a
"quiet change" that some programs employing two question marks in
character or string constants may now produce different results.

So in general, you must check existing programs for two question marks
followed by one of the following:
	= ( / ) ' < ! > -
and make an appropriate adjustment.  (You can always get precisely the
same result, you just might need to change the source form slightly.)
-- 

Steve Clamage, TauMetric Corp, steve@taumet.com

In article <1829@ns-mx.uiowa.edu> cmdglv@vaxa.weeg.uiowa.edu writes:
>P.S., Does anybody else out there resent being patronized, belittled, and
>disbelieved when they try to report a bug to Microsoft Technical Support?
>

Yes and no. Almost every time I have talked to Microsoft, I ended up with
some idiot on the other side of the phone. As an example I presented some
code to them which as a TSR under DOS worked great until QuickBASIC was
running. I sent them .ASM source and said: This needs to be assembled and 
linked as a .COM file. The response was: The resulting .EXE crashes. I 
told them to run it through EXE2BIN and they said what's that?

With that sort of mentality, I can only laugh - It's tough to be belittled by
a moron. The one time I talked to somebody with intelligence, I got very 
straight forward answers (He was quickly moved to another department!)

Cheers!
Steve
.


-- 
--------------------------------------------------------------------------------
Steve Resnick -<stever@octopus.COM apple!octopus!stever sun!vsi1!octopus!stever>
408/241-1533 Process Scientific, Inc.
"0x2B|~0x2B THAT is the question!"