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"Charles Richmond" <> writes:

> "Patrick Scheible" <> wrote in message
> news:...
>> Keith Thompson <kst-> writes:
>>
>>> (Richard Harter) writes:
>>>> The other day I wanted to put three successive question marks in a
>>>> string. Frex, "(???).%s.%s". My trusty antique gcc compiler
>>>> converted the last two '?'s into a ']' along with a warning that it
>>>> was doing a trigraph conversion.
>>>>
>>>> Now, me, I know from nothing about trigraphs - never used them, hope
>>>> never to use them - so I was caught by surprise. My elderly copy of
>>>> K&R described them but I didn't see anything about getting around
>>>> them.
>>>>
>>>> So. How is one supposed to get three successive question marks into a
>>>> string?
>>>
>>> For reference, there are exactly 9 trigraphs. C99 5.2.1.1:
>>>
>>> All occurrences in a source file of the following sequences of three
>>> characters (called trigraph sequences) are replaced with the
>>> corresponding single character.
>>>
>>> ??= # ??) ] ??! |
>>> ??( [ ??' ^ ??> }
>>> ??/ \ ??< { ??- ~
>>>
>>> No other trigraph sequences exist. Each ? that does not begin one of
>>> the trigraphs listed above is not changed.
>>>
>>> In your case, "???" is not a trigraph, but ??) is.
>>
>> Has the C standards committee been flamed enough for trigraphs? I don't
>> think so. I bet there's 1000 programmers bitten by them for every 1
>> who's been helped. By 1989 anyone who didn't have an editor capable of
>> typing any 7-bit ASCII character was a hopeless luddite who would be
>> better served making their own pre-preprocessing phase for C and leaving
>> the language unchanged instead of another phase in the preprocessor for
>> every C program forever and ever.
>>
>
> So just *remove* trigraphs from the *next* C standard. Or require the
> preprocessor symbol "__TRIGRAPH_IMPLEMENTED__" to be defined, or
> relegate this to a PRAGMA... before trigraphs would be recognized by
> the compiler. Make it *extra* hard for the ordinary C programmer to
> step on this land mine.

Yes, this is the best thing to do now, since it's to late to have never
put them in the language in the first place.

-- Patrick

On 31-Jan-12 23:50, Charles Richmond wrote:
>> Keith Thompson <kst-> writes:
>>> For reference, there are exactly 9 trigraphs. C99 5.2.1.1:
>>>
>>> All occurrences in a source file of the following sequences of three
>>> characters (called trigraph sequences) are replaced with the
>>> corresponding single character.
>>>
>>> ??= # ??) ] ??! |
>>> ??( [ ??' ^ ??> }
>>> ??/ \ ??< { ??- ~
....
> So just *remove* trigraphs from the *next* C standard. Or require the
> preprocessor symbol "__TRIGRAPH_IMPLEMENTED__" to be defined,

How would that help? If someone knows to check for that symbol,
presumably they also know not to inadvertently use trigraphs.

> or relegate this to a PRAGMA... before trigraphs would be recognized
> by the compiler.

You couldn't use a #pragma to enable trigraphs since # is one of the
characters that may require a trigraph. See above.

S

--
Stephen Sprunk "God does not play dice." --Albert Einstein
CCIE #3723 "God is an inveterate gambler, and He throws the
K5SSS dice at every possible opportunity." --Stephen Hawking

Stephen Sprunk <> writes:

> On 31-Jan-12 23:50, Charles Richmond wrote:
>> or relegate this to a PRAGMA... before trigraphs would be recognized
>> by the compiler.
>
> You couldn't use a #pragma to enable trigraphs since # is one of the
> characters that may require a trigraph. See above.

You could use a %ragma to enable trigraphs.
--
char a[]="\n .CJacehknorstu";int putchar(int);int main(void){unsigned long b[]
={0x67dffdff,0x9aa9aa6a,0xa77ffda9,0x7da6aa6a,0xa6 7f6aaa,0xaa9aa9f6,0x11f6},*p
=b,i=24;for(;p+=!*p;*p/=4)switch(0[p]&3)case 0:{return 0;for(p--;i--;i--)case+
2:{i++;if(i)break;else default:continue;if(0)case 1utchar(a[i&15]);break;}}}

On 2012-02-01, Ben Pfaff <> wrote:
> Stephen Sprunk <> writes:
>
>> On 31-Jan-12 23:50, Charles Richmond wrote:
>>> or relegate this to a PRAGMA... before trigraphs would be recognized
>>> by the compiler.
>>
>> You couldn't use a #pragma to enable trigraphs since # is one of the
>> characters that may require a trigraph. See above.
>
> You could use a %ragma to enable trigraphs.

Even better:

??=pragma

Kaz Kylheku <> writes:

> On 2012-02-01, Ben Pfaff <> wrote:
>> Stephen Sprunk <> writes:
>>
>>> On 31-Jan-12 23:50, Charles Richmond wrote:
>>>> or relegate this to a PRAGMA... before trigraphs would be recognized
>>>> by the compiler.
>>>
>>> You couldn't use a #pragma to enable trigraphs since # is one of the
>>> characters that may require a trigraph. See above.
>>
>> You could use a %ragma to enable trigraphs.
>
> Even better:
>
> ??=pragma

You couldn't use ??=pragma to enable trigraphs because ??= is a
trigraph. See above.
--
char a[]="\n .CJacehknorstu";int putchar(int);int main(void){unsigned long b[]
={0x67dffdff,0x9aa9aa6a,0xa77ffda9,0x7da6aa6a,0xa6 7f6aaa,0xaa9aa9f6,0x11f6},*p
=b,i=24;for(;p+=!*p;*p/=4)switch(0[p]&3)case 0:{return 0;for(p--;i--;i--)case+
2:{i++;if(i)break;else default:continue;if(0)case 1utchar(a[i&15]);break;}}}

On 01-Feb-12 13:35, Ben Pfaff wrote:
> Stephen Sprunk <> writes:
>
>> On 31-Jan-12 23:50, Charles Richmond wrote:
>>> or relegate this to a PRAGMA... before trigraphs would be recognized
>>> by the compiler.
>>
>> You couldn't use a #pragma to enable trigraphs since # is one of the
>> characters that may require a trigraph. See above.
>
> You could use a %ragma to enable trigraphs.

Or, to avoid creating yet another bizarre sequence of symbols, you could
create a special exception for "??=pragma trigraph", without recognizing
any other trigraphs by default.

However, that still seems like a hack; it seems more straightforward to
allow implementations to optionally ignore trigraphs via some external
means, which is the status quo anyway.

S


--
Stephen Sprunk "God does not play dice." --Albert Einstein
CCIE #3723 "God is an inveterate gambler, and He throws the
K5SSS dice at every possible opportunity." --Stephen Hawking

On 2012-02-01, Stephen Sprunk <> wrote:
> On 01-Feb-12 13:35, Ben Pfaff wrote:
>> Stephen Sprunk <> writes:
>>
>>> On 31-Jan-12 23:50, Charles Richmond wrote:
>>>> or relegate this to a PRAGMA... before trigraphs would be recognized
>>>> by the compiler.
>>>
>>> You couldn't use a #pragma to enable trigraphs since # is one of the
>>> characters that may require a trigraph. See above.
>>
>> You could use a %ragma to enable trigraphs.
>
> Or, to avoid creating yet another bizarre sequence of symbols, you could
> create a special exception for "??=pragma trigraph", without recognizing
> any other trigraphs by default.

No special exception! ??=pragma trigraph enables trigraphs, but ??= is not
recognized until trigraphs are enabled.

That is the perfect solution.

On 2012-02-01, Ben Pfaff <> wrote:
> Kaz Kylheku <> writes:
>
>> On 2012-02-01, Ben Pfaff <> wrote:
>>> Stephen Sprunk <> writes:
>>>
>>>> On 31-Jan-12 23:50, Charles Richmond wrote:
>>>>> or relegate this to a PRAGMA... before trigraphs would be recognized
>>>>> by the compiler.
>>>>
>>>> You couldn't use a #pragma to enable trigraphs since # is one of the
>>>> characters that may require a trigraph. See above.
>>>
>>> You could use a %ragma to enable trigraphs.
>>
>> Even better:
>>
>> ??=pragma
>
> You couldn't use ??=pragma to enable trigraphs because ??= is a
> trigraph. See above.

So you understand the point perfectly!

In article <>,
Patrick Scheible <> wrote:
>Has the C standards committee been flamed enough for trigraphs?

I don't think so.

http://upload.wikimedia.org/wikipedi...an-picture.jpg

http://www.youtube.com/watch?v=NUHy3IgqlHc

"christian.bau" <> writes:

> On Feb 1, 5:50Â*am, "Charles Richmond" <netn...@aquaporin4.com> wrote:
>
>> So just *remove* trigraphs from the *next* C standard. Â*Or require the
>> preprocessor symbol "__TRIGRAPH_IMPLEMENTED__" to be defined, or relegate
>> this to a PRAGMA... Â*before trigraphs would be recognized by the compiler.
>> Make it *extra* hard for the ordinary C programmer to step on this land
>> mine.
>
> A change that would silently break existing code.

How much existing code uses trigraphs?

-- Patrick