From: "Gonzalo Garramuño" <ggarra@...>
Date: 2007-12-14T19:32:33+09:00
Subject: Re: IRHG - PUSH_FRAME?

Charles Thornton wrote:
> The following define statement is driving me crazy
> I have never seen a  #define used this way!
> 

You haven't been coding in C too long.  While splitting the do/while 
between two different macros as done here is not what I would call too 
good coding, using long macros like these is often needed in C 
programming (and sometimes C++ too).
The do/while construct is an often used to define a block and avoid name 
collision in temporary variables (and also to allow the macro to be used 
in if-thens).

> Can someone explain what is going on here?
> 
> Does this somehow create a new frame without
> allocation, and add it to a ruby_frame linked list?
> 

Yes.  PUSH_FRAME and POP_FRAME are to be used together and create a block.

PUSH_FRAME();
      // some other stuff
POP_FRAME();

which expands to:

   do {
       ... add frame...
       // some other stuff
       ... revert frame ...
    } while (0);




-- 
Gonzalo Garramu�o
ggarra@advancedsl.com.ar

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