2a954ceeb6
A scalar `::` constant folds to its value and has no storage. The unary `.address_of` lowering (src/ir/lower/expr.zig) skipped the alloca path (is_alloca == false) and resolveGlobalRef (scalar consts get no storage global), falling through to the generic addr_of arm, which reinterpreted the folded value as a pointer: `inttoptr (i64 <value> to ptr)`. That wild pointer segfaulted on deref and emitted invalid stores for inline-asm `-> @const`. Diagnose instead, in the address_of(identifier) path: a non-alloca, non-ref-capture, non-pack-elem scope binding (local scalar const) and a module_const_map name not backed by storage (module scalar const) both report "cannot take the address of constant '<name>' — a scalar '::' constant has no storage …" and return a placeholder Ref. Chose diagnose over materializing read-only storage (consistent with the fold-only scalar model). Array/struct consts keep real storage and stay addressable (@K/@LIT unchanged). Also gives the ASM stream's planned output-to-const rejection for free — asm `-> @const` lowers through the same path. Regression: examples/1177-diagnostics-addr-of-const-rejected.sx. Resolves 0138.
19 lines
794 B
Plaintext
19 lines
794 B
Plaintext
// Taking the address of a scalar `::` constant is a compile error: a scalar
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// constant folds to its value and has NO storage (only array/struct constants
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// are immutable globals with a real address — see 0177). Covers a module-scope
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// const, a local const, and an inline-asm `-> @const` write-through (the path
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// that surfaced the bug). Before the fix, `@N` lowered to `inttoptr (i64 40 to
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// ptr)` — a wild pointer that segfaulted on deref and emitted invalid stores
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// for asm `-> @const`. Regression (issue 0138).
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takes :: (p: *i64) {}
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N :: 40;
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main :: () {
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takes(@N); // module scalar const — no storage
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x :: 7;
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takes(@x); // local scalar const — no storage
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asm volatile { "mov %[c], #99", [c] "=r" -> @N }; // write-through to a const
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}
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