Blocks

[David Chisnall]

Hi Everyone,

I've just added a couple of macros to GNUstep that let us use blocks  
(but not create) without requiring the compiler to support them.  This  
means that we can implement any of the 10.6 methods that take blocks  
as arguments, without breaking GCC compatibility.

Blocks are basically structures with one field pointing to a function  
with a hidden first argument (sound familiar?) that is used to pass  
the block in.  If you use the DECLARE_BLOCK_TYPE macro then it will  
define a block type if one is supported by your compiler.  If not,  
then it will define a structure with the same layout as a block.  The  
CALL_BLOCK macro either calls the function in the structure, or lets  
the compiler call the block.

To show how to use these, I've implemented NSArray's - 
enumerateObjectsUsingBlock: method from 10.6.

Let me know if you've got any questions,

David

P.S. Creating blocks requires clang and a blocks runtime, such as the  
one in libobjc2.

-- Sent from my Difference Engine