161254f5bb
Repro found while writing PLAN-FFI step 0.10.
In a single file:
__stdinp : *void #foreign;
stdinp_addr :: () -> u64 { xx @__stdinp; }
main :: () -> s32 {
a : u64 = xx @__stdinp; // a = real symbol address
b := stdinp_addr(); // b = 0
...
}
The emitted IR for the helper is `ret i64 undef`, suggesting the
`address_of(identifier=__stdinp)` branch in lower.zig (~line 1719)
doesn't see `__stdinp` in `global_names` at the moment the helper's
body is being lowered — even though the same lookup succeeds inside
main's body in the same compilation unit.
Likely cause: lazy-body lowering ordering vs. the pass that
registers extern global decls into `global_names`. Worth verifying
which before fixing — could also be per-function scoping of the
map. Phase 1 of the FFI plan doesn't depend on this, so it stays
filed as an open issue and gets addressed when convenient (or when
sx-side `extern` cross-file globals from issue-0030 land and need
the same lookup to work everywhere).
48 lines
1.6 KiB
Plaintext
48 lines
1.6 KiB
Plaintext
// `@__stdinp` (address-of a `#foreign` global) lowers to `undef` /
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// 0 when accessed from inside a non-main function body. From `main`
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// directly it works:
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//
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// single file:
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// __stdinp : *void #foreign;
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// stdinp_addr :: () -> u64 { xx @__stdinp; }
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// main :: () -> s32 {
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// a : u64 = xx @__stdinp; // a = <real symbol address>
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// b := stdinp_addr(); // b = 0
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// ...
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// }
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//
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// The emitted IR for the helper is just `ret i64 undef`, suggesting
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// the `address_of(identifier=__stdinp)` branch in `lower.zig`
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// (~line 1719) doesn't see `__stdinp` in `global_names` at the time
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// the helper's body is being lowered — even though the same lookup
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// succeeds inside main.
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//
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// Likely cause: lazy/lazy-deferred body lowering ordering vs. the
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// pass that registers extern global decls into `global_names`. Or
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// global_names is scoped per-function (?). Worth verifying which
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// before fixing.
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//
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// Expected when fixed: the helper returns the same address as the
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// direct read, prints `eq = true`. Today: prints `eq = false`.
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//
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// Filed during PLAN-FFI step 0.10 (cross-file `#foreign` global —
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// the cross-file dimension surfaced the bug, but it reproduces in
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// a single file too).
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#import "modules/std.sx";
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__stdinp : *void #foreign;
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stdinp_addr_via_helper :: () -> u64 {
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xx @__stdinp;
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}
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main :: () -> s32 {
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direct : u64 = xx @__stdinp;
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via_helper := stdinp_addr_via_helper();
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print("direct non-null = {}\n", direct != 0);
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print("helper non-null = {}\n", via_helper != 0);
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print("eq = {}\n", direct == via_helper);
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0;
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}
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