What does “typedef void (^Something)()” mean [duplicate] - c++-cli

Question

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Caret in objective C
(3 answers)
Closed 4 years ago.
I was trying to compile stk. During the configuration I get the error
System/Library/Frameworks/CoreAudio.framework/Headers/AudioHardware.h:162:2:
error: expected identifier or '(' before '^' token
(^AudioObjectPropertyListenerBlock)(
When I see the code I see ^ inside the function pointer declaration at line 162 in here. I know we can have * but what does ^ mean?
Code snippet :
#if defined(__BLOCKS__)
typedef void
(^AudioObjectPropertyListenerBlock)( UInt32 inNumberAddresses,
const AudioObjectPropertyAddress inAddresses[]);

Answer 1

As other answerers here say, it could be in C++/CLI.
But also, if you are on a macOS (like you hinted in one comment), this is an Objective-C block.
Its syntax is very very weird.
The block is like a C++ closures and Java anonymous inner classes, it can capture variables.
__block int insider = 0;
void(^block)() = ^{
// print insider here using your favourite method, printf for example
};
This is a complete NSObject (base Objective-C class), but is callable, this is not a mere function pointer.
Refer to this Apple document: https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/WorkingwithBlocks/WorkingwithBlocks.html
Now, we go to the important question, I want to run this on Linux, how ???
LLVM supports block syntax, but you should refer to this StackOverflow question for more: Clang block in Linux?
So, you should compile your code in the LLVM compiler, and use -fblocks and -lBlocksRuntime.
Don't forget to install those Linux packages:
llvm
clang
libblocksruntime-dev
If you are already on macOS, just use -fblocks.