CODEWITHSUNDEEP
objective-ccocoa-touchobjective-c-blocks
0xSina
0xSina

Reputation: 21553

How does the __block specifier work?

I can specify an a variable on stack with a __block specifier and then I am able to modify it in a block. I am just wondering, behind the scenes what happens? (If the block is executed sometime in the future, then the stack might be cleared)

Upvotes: 3

Views: 1341

Answers (1)

Ken Thomases
Ken Thomases

Reputation: 90541

When a block which references a __block variable is copied, the variable is moved to the heap. This means that all code which references it has to do so through an indirect means, basically a pointer, so that, when it moves from the stack to the heap, those references can switch along with it.

This is documented here.

Upvotes: 4

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