On 17 Jun 2018, at 22:48, Fred Kiefer <fredkie...@gmx.de> wrote:
>
> I was hoping for someone with a working knowledge of blocks to step in here.
> But currently I seem to be the only one operating this mailing list :-)
>
> If you have a look in the file Tests/base/NSArray/blocks.m you will find
> examples on how to write an NSBlock for a compiler that supports it. A very
> simple one would be this:
> ^() { return YES; }
>
> You should also be able to simulate blocks with gcc, but I am not sure how to
> do this :-(
You can, in theory, simulate blocks with any C compiler, but in practice it’s
too hard. A block is a structure that contains pointers to other structures
that describe all of the captured variables and how to copy them. For anything
beyond a simple function written as a block, the compiler is generating a load
of helper code for copying the captures.
The GSBlock stuff allows a legacy compiler to *call* blocks (by casting them to
a compatible structure type and calling the invoke function with a pointer to
the struct as the first argument) but it doesn’t make any attempt to allow
compilers for pre-2007 dialects of Objective-C to generate blocks. The logic
in the compiler for doing so is several hundred lines of code and integrates
with understanding of object lifetimes - replicating this in C macros is not
feasible.
David
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