Keyword _Imaginary in C99 standard and in GCC

Keyword _Imaginary in C99 standard and in GCC

[Yao qi]

Hi, everyone,
I have looked through C99 standard, in 6.4.1 Keywords,  "_Imaginary" is 
mentioned as a keyword in this standard.  However, it seems that GCC can not 
recognize it,  report error: '_Imaginary' undeclared.  I also search it in 
GCC info, there is no spot mentioned that.  Maybe GCC does not include it as 
a keyword, I am not sure about that, am I missing something?  Maybe someone 
of you could clarify for me.  Thanks in advance.

Best Regards
----------------
Yao Qi
Bejing Institute of Technology

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Re: Keyword _Imaginary in C99 standard and in GCC

[Andrew Pinski]

On Aug 18, 2005, at 11:04 PM, Yao qi wrote:

> Hi, everyone,
> I have looked through C99 standard, in 6.4.1 Keywords,  "_Imaginary" 
> is mentioned as a keyword in this standard.  However, it seems that 
> GCC can not recognize it,  report error: '_Imaginary' undeclared.  I 
> also search it in GCC info, there is no spot mentioned that.  Maybe 
> GCC does not include it as a keyword, I am not sure about that, am I 
> missing something?  Maybe someone of you could clarify for me.  Thanks 
> in advance.

_Imaginary types are not implemented yet in GCC.

-- Pinski

Re: Keyword _Imaginary in C99 standard and in GCC

[Yao qi]

>From: Andrew Pinski <pinskia@physics.uc.edu>
>To: "Yao qi" <qiyaobit@hotmail.com>
>CC: gcc@gcc.gnu.org
>Subject: Re: Keyword _Imaginary in C99 standard and in GCC
>Date: Thu, 18 Aug 2005 23:07:49 -0400
>
>
>On Aug 18, 2005, at 11:04 PM, Yao qi wrote:
>
>>Hi, everyone,
>>I have looked through C99 standard, in 6.4.1 Keywords,  "_Imaginary" is 
>>mentioned as a keyword in this standard.  However, it seems that GCC can 
>>not recognize it,  report error: '_Imaginary' undeclared.  I also search 
>>it in GCC info, there is no spot mentioned that.  Maybe GCC does not 
>>include it as a keyword, I am not sure about that, am I missing something? 
>>  Maybe someone of you could clarify for me.  Thanks in advance.
>
>_Imaginary types are not implemented yet in GCC.
>
>-- Pinski
>
Thanks.  That means GCC has not fully support C99, just partialy, am I 
right?  I want to continue a question further, could you tell me where can I 
find a document about GCC's coverage in C99, if any?  If there is no such 
document, I just have to collect these information by hand.

Best Regards
----------------
Yao Qi
Bejing Institute of Technology

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Re: Keyword _Imaginary in C99 standard and in GCC

[Andrew Pinski]

On Aug 18, 2005, at 11:25 PM, Yao qi wrote:
> Thanks.  That means GCC has not fully support C99, just partialy, am I 
> right?  I want to continue a question further, could you tell me where 
> can I find a document about GCC's coverage in C99, if any?

http://gcc.gnu.org/c99status.html

Note there is a DR report about _Imaginary types:
http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_207.htm

-- Pinski

Re: Keyword _Imaginary in C99 standard and in GCC

[Yao qi]

Hi,Pinski,

Got it!  Thanks.

Best Regards
----------------
Yao Qi
Bejing Institute of Technology





>From: Andrew Pinski <pinskia@physics.uc.edu>
>To: "Yao qi" <qiyaobit@hotmail.com>
>CC: gcc@gcc.gnu.org
>Subject: Re: Keyword _Imaginary in C99 standard and in GCC
>Date: Thu, 18 Aug 2005 23:30:06 -0400
>
>
>On Aug 18, 2005, at 11:25 PM, Yao qi wrote:
>>Thanks.  That means GCC has not fully support C99, just partialy, am I 
>>right?  I want to continue a question further, could you tell me where can 
>>I find a document about GCC's coverage in C99, if any?
>
>http://gcc.gnu.org/c99status.html
>
>Note there is a DR report about _Imaginary types:
>http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_207.htm
>
>-- Pinski
>

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Re: Keyword _Imaginary in C99 standard and in GCC

[Joseph S. Myers]

On Fri, 19 Aug 2005, Yao qi wrote:

> Hi, everyone,
> I have looked through C99 standard, in 6.4.1 Keywords,  "_Imaginary" is
> mentioned as a keyword in this standard.  However, it seems that GCC can not
> recognize it,  report error: '_Imaginary' undeclared.  I also search it in GCC
> info, there is no spot mentioned that.  Maybe GCC does not include it as a
> keyword, I am not sure about that, am I missing something?  Maybe someone of
> you could clarify for me.  Thanks in advance.

What use do you have for a keyword which is reserved but cannot be used 
anywhere?  As of TC2, _Imaginary is just that; it is not a type specifier, 
and an implementation implementing Annex G (which is not normative) is 
incompatible with the normative parts of the standard (at least as regards 
the header definition of "I" having conflicting definitions in the 
standard and in Annex G).  There are serious doubts (as discussed on the 
WG14 reflector in the past) about the utility of imaginary types as 
defined in Annex G.

Now, adding _Imaginary as a keyword which is not permitted anywhere in the 
syntax (so you get parse errors and can't e.g. declare variables called 
_Imaginary) would be a trivial patch, but not clearly a very useful one.

-- 
Joseph S. Myers
joseph@codesourcery.com