[Bug c/78352] New: GCC lacks support for the Apple "blocks" extension to the C family of languages

["egall at gwmail dot gwu.edu" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78352

            Bug ID: 78352
           Summary: GCC lacks support for the Apple "blocks" extension to
                    the C family of languages
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: egall at gwmail dot gwu.edu
  Target Milestone: ---

In bug 78267 Iain suggested to open a separate bug for the issue of missing
Apple-blocks support in FSF GCC, so that's what this bug is. Here is an example
of code that is currently rejected due to lack of support for this feature:

typedef void (^os_trace_payload_t)(xpc_object_t xdict);

In Apple's gcc and clang, support for blocks can be enabled with the -fblocks
flag, and can be detected by the presence of the __BLOCKS__ preprocessor macro.
This extension applies to all members of the C family: C, C++, Objective C, and
Objective C++. 

Further information:
https://gcc.gnu.org/ml/gcc/2009-09/msg00277.html (and the rest of the thread)
https://gcc.gnu.org/ml/gcc/2013-11/msg00039.html (likewise, & rest of thread)
Bug 63651
http://clang.llvm.org/docs/BlockLanguageSpec.html
http://clang.llvm.org/docs/Block-ABI-Apple.html
http://www.open-std.org/JTC1/sc22/wg14/www/docs/n1370.pdf
https://en.wikipedia.org/wiki/Blocks_%28C_language_extension%29