class Q_CORE_EXPORT QFlag

class Q_CORE_EXPORT QFlag

[Shriramana Sharma]

I see many usages in the Qt sources like:

class Q_CORE_EXPORT QFlag
{
	<blah blah blah>
} ;

Isn't the word immediately next to the keyword class supposed to be the 
class name? Q_CORE_EXPORT etc are certainly not class names. What are 
they and how are they allowed in between the word class and the class name?

I searched my "Thinking in C++" for this but did not turn up an answer. 
Please help.

Thanks as always,

Shriramana Sharma.

Re: class Q_CORE_EXPORT QFlag

[leslie.polzer]

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On Tue, May 01, 2007 at 05:24:54PM +0530, Shriramana Sharma wrote:

> I see many usages in the Qt sources like:
>
> class Q_CORE_EXPORT QFlag { <blah blah blah> } ;
>
> Isn't the word immediately next to the keyword class supposed to be
> the class name? Q_CORE_EXPORT etc are certainly not class names. What
> are they and how are they allowed in between the word class and the
> class name?

It's either a C preprocessor symbol defined somewhere else, or, what's
more likely, a MOC preprocessor symbol.

  Leslie

-- 
Personal homepage: https://viridian.dnsalias.net/~sky/homepage/
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Re: class Q_CORE_EXPORT QFlag

[Steve Graegert]

On 5/1/07, Shriramana Sharma <samjnaa@gmail.com> wrote:
> I see many usages in the Qt sources like:
>
> class Q_CORE_EXPORT QFlag
> {
>         <blah blah blah>
> } ;
>
> Isn't the word immediately next to the keyword class supposed to be the
> class name? Q_CORE_EXPORT etc are certainly not class names. What are
> they and how are they allowed in between the word class and the class name?
>
> I searched my "Thinking in C++" for this but did not turn up an answer.
> Please help.

It's a macro that expands with different results depending on the
platform and/or context.  For example when building Qt applications on
a Windows machine, it's redefined to Q_DECL_EXPORT which, in this
case, expands to __declspec(dllexport).  See
/src/corelib/global/qglobal.h in the Qt source tree.

	\Steve

--

Steve Grägert <steve@graegert.com>
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Re: class Q_CORE_EXPORT QFlag

[Shriramana Sharma]

Thanks Leslie and Steve. It did not occur to me that it would be 
something MOC takes care of.

I need to read up on what these mangled __ symbols mean. I have seen 
some in glibc sources (just perused a few files) especially things like 
__throw -- probably flags to the C++ compiler indicating what a 
particular class or function or whatever behaves like, yes?

Shriramana Sharma.

Re: class Q_CORE_EXPORT QFlag

[Shriramana Sharma]

Shriramana Sharma wrote:
> I need to read up on what these mangled __ symbols mean. 

Um I am at a loss to where to start... Can anyone point me to good 
reading on this topic? Thanks.

Shriramana Sharma.

Re: class Q_CORE_EXPORT QFlag

[Glynn Clements]

Shriramana Sharma wrote:

> Thanks Leslie and Steve. It did not occur to me that it would be 
> something MOC takes care of.
> 
> I need to read up on what these mangled __ symbols mean. I have seen 
> some in glibc sources (just perused a few files) especially things like 
> __throw -- probably flags to the C++ compiler indicating what a 
> particular class or function or whatever behaves like, yes?

Identifiers beginning with an underscore are reserved for the
"implementation", i.e. the compiler and/or standard libraries (libc
and libm). Specifically:

         -- All  identifiers  that  begin  with  an  underscore and
            either an uppercase letter or  another  underscore  are
            always reserved for any use.

         -- All  identifiers  that  begin  with  an  underscore are
            always reserved for use as identifiers with file  scope
            in both the ordinary and tag name spaces.

Most of them will be documented in the Info files for gcc and glibc.

-- 
Glynn Clements <glynn@gclements.plus.com>