556e4e12ea
The compiler-synthesised trampoline path (previous commit) covers every closure signature on demand; the hand-rolled stdlib impls were only for two specific shapes (`Closure() -> void`, `Closure(bool) -> void`) and are now strictly redundant. Kept: the `Block` struct, `BlockDescriptor`, the `_NSConcreteStackBlock` extern decl, and the shared `__sx_block_descriptor` global. The compiler-emitted code references all four; users still need to `#import "modules/std/objc_block.sx";` to bring them into the module. Removed: `__block_invoke_void`, `__block_invoke_bool`, and both `impl Into(Block) for Closure(...) -> void` blocks. Replaced with a comment block explaining how the compiler now handles the cast. After this commit, `xx my_closure : Block` works for ANY closure signature with no per-signature stdlib boilerplate. 189/189 example tests pass; chess on iOS-sim green.
69 lines
3.0 KiB
Plaintext
69 lines
3.0 KiB
Plaintext
// Obj-C blocks bridged to sx closures.
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//
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// Apple's block ABI (clang's "Block Implementation Specification"): a block
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// pointer is a struct whose first five fields are { isa, flags, reserved,
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// invoke, descriptor } followed by per-block captured state. When an API
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// like `[UIView animateWithDuration:animations:]` receives a block, the
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// runtime reads `invoke` and calls it with the block pointer as the first
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// argument. UIKit / Foundation callers always `_Block_copy` synchronously
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// before returning, so a stack-allocated block is safe to pass directly.
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//
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// We layer the sx closure onto Apple's layout by appending two pointer
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// fields to the standard 32-byte header: `sx_env` (the closure's captured
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// environment pointer) and `sx_fn` (the closure trampoline). The per-
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// signature `__block_invoke_*` C-ABI fn knows the offsets and calls
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// through to `sx_fn(sx_env, args...)`.
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//
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// ── Lifetime contract ───────────────────────────────────────────────────
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// `xx <closure> : *Block` returns a pointer into the surrounding sx
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// function's stack frame. Same rule as `&local_var`: pass it directly to
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// a callee that consumes it immediately or `_Block_copy`s internally
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// (UIKit/Foundation always do). Don't store the pointer to use after the
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// caller returns. If you need that, ship a `Block_copy`-backed sibling
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// API and use it instead.
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// Standard 32-byte block header plus two trailing slots for the sx closure
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// it wraps. Total = 48 bytes.
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Block :: struct {
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isa: *void;
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flags: s32;
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reserved: s32;
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invoke: *void;
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descriptor: *void;
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sx_env: *void;
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sx_fn: *void;
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}
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// Per-block-shape metadata. The runtime reads `size` when copying the
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// block to the heap, so it must equal the actual instance size.
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BlockDescriptor :: struct {
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reserved: u64;
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size: u64;
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}
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// libSystem isa pointer for stack-allocated blocks. Resolved at link time
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// (auto-linked on every Apple target via libSystem).
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_NSConcreteStackBlock : *void #foreign;
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// Shared descriptor for the 48-byte sx-block layout. All Into impls below
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// point their `descriptor` field at this.
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__sx_block_descriptor : BlockDescriptor = .{
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reserved = 0,
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size = 48,
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};
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// M5.A — `xx closure : Block` casts are handled by the compiler.
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// For every closure signature seen at a cast site, the compiler
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// synthesises:
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// 1. A C-ABI trampoline `__block_invoke_<sig>` matching Apple's
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// `__block_literal.invoke` calling convention.
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// 2. Inline Block-struct construction at the cast site, with
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// `invoke` pointing at the synthesised trampoline and
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// `sx_env`/`sx_fn` taken from the closure value.
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//
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// User-facing surface: `xx my_closure : Block` for ANY closure
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// signature. No per-signature stdlib boilerplate. The shared
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// infrastructure above (`Block`, `BlockDescriptor`,
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// `_NSConcreteStackBlock`, `__sx_block_descriptor`) is referenced
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// by the synthesised code; users only need to `#import` this module.
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