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What are these functions (warning, push, disable) are in the macro definition?

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  What are these functions (warning, push, disable) are in the macro definition? fl <rxjwg98@gmail.com> - 2017-04-05 07:49 -0700
    Re: What are these functions (warning, push, disable) are in the macro definition? scott@slp53.sl.home (Scott Lurndal) - 2017-04-05 15:25 +0000
    Re: What are these functions (warning, push, disable) are in the macro definition? Keith Thompson <kst-u@mib.org> - 2017-04-05 13:46 -0700
    Re: What are these functions (warning, push, disable) are in the macro definition? Ken Brody <kenbrody@spamcop.net> - 2017-04-06 11:38 -0400

#107759 — What are these functions (warning, push, disable) are in the macro definition?

Hi,

I have a MSVC project which has the following definitions. It builds 
successfully on MSVC, but I don't understand what warning, push, pop 
and disable are.

Could you tell me that?

Thanks,


.........................
#if DSAS_MSVC
#define DSAS_MULTILINE_MACRO_END \
  __pragma( warning( push ) ) \
  __pragma( warning( disable:4127 ) ) \
  } \
  while( 0 ) \
  __pragma( warning( pop ) )
#else /* #if DSAS_MSVC  */
#define DSAS_MULTILINE_MACRO_END \
  } \
  while ( 0 )
#endif 

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#107761

fl <rxjwg98@gmail.com> writes:
>Hi,
>
>I have a MSVC project which has the following definitions. It builds 
>successfully on MSVC, but I don't understand what warning, push, pop 
>and disable are.
>
>Could you tell me that?
>
>Thanks,
>
>
>.........................
>#if DSAS_MSVC
>#define DSAS_MULTILINE_MACRO_END \
>  __pragma( warning( push ) ) \

Push the current warning state on an internal compiler stack.

>  __pragma( warning( disable:4127 ) ) \

Disable warning 4127, whatever that is

>  } \
>  while( 0 ) \
>  __pragma( warning( pop ) )

Restore the pushed warning state.

>#else /* #if DSAS_MSVC  */
>#define DSAS_MULTILINE_MACRO_END \
>  } \
>  while ( 0 )
>#endif 

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#107768

fl <rxjwg98@gmail.com> writes:
> I have a MSVC project which has the following definitions. It builds 
> successfully on MSVC, but I don't understand what warning, push, pop 
> and disable are.
[...]
>
> .........................
> #if DSAS_MSVC
> #define DSAS_MULTILINE_MACRO_END \
>   __pragma( warning( push ) ) \
>   __pragma( warning( disable:4127 ) ) \
>   } \
>   while( 0 ) \
>   __pragma( warning( pop ) )
> #else /* #if DSAS_MSVC  */
> #define DSAS_MULTILINE_MACRO_END \
>   } \
>   while ( 0 )
> #endif 

This is a non-standard feature of MSVC, documented here:

https://msdn.microsoft.com/en-us/library/2c8f766e.aspx

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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#107784

On 4/5/2017 10:49 AM, fl wrote:
> Hi,
>
> I have a MSVC project which has the following definitions. It builds
> successfully on MSVC, but I don't understand what warning, push, pop
> and disable are.
>
> Could you tell me that?
>
> Thanks,
>
>
> .........................
> #if DSAS_MSVC
> #define DSAS_MULTILINE_MACRO_END \
>   __pragma( warning( push ) ) \
>   __pragma( warning( disable:4127 ) ) \
>   } \
>   while( 0 ) \
>   __pragma( warning( pop ) )
> #else /* #if DSAS_MSVC  */
> #define DSAS_MULTILINE_MACRO_END \
>   } \
>   while ( 0 )
> #endif

First, all pragma statements (except for those starting with "STDC") are 
implementation-defined, so you would have to check with a Microsoft-related 
group for full details.

However, since I work in MSVC, I recognize it as a basic "temporarily 
disable warning number 4127, and then restore it to whatever state it was 
before".  (That's the "push" and "pop" part.)  Apparently, the actual 
contents of the macro will generate that warning, and the author wants to 
tell the compiler "yes, I know, but it's all good, so shut up about it already".

You can check in a Microsoft-related group, or the MSVC docs for information 
on what, exactly, is warning number 4127.  Or, a quick web search for "msvc 
warning 4127" will answer it as well.

-- 
Kenneth Brody

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