rust: store local wrapper addresses in async stream/future vtables - #1699
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alexcrichton merged 5 commits intoAug 27, 2026
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This is in preparation to try to test and expose a bug in the toolchain in a subsequent commit and fix it.
Under a position-independent dynamic library build, an intrinsic that is only address-taken (stored in the StreamVtable/FutureVtable, never called by name) is lowered by LLVM to a GOT.func global keyed by its mangled Rust symbol, and the canonical (module, field) wasm import is dropped. The component linker resolves GOT.func slots against library exports, but no library exports that mangled symbol and the canonical name is gone, so components using dynamic libraries fail to link. Emit a local wrapper for each of the intrinsics on wasm and store the wrapper's address in the vtable. The wrapper calls the canonical import by name (keeping the import live) and the address-take becomes an ordinary table relocation against a defined function, which the linker resolves.
dicej
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Aug 26, 2026
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Should probably have a doc comment since the other fields do.
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| /// TODO |
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TODO as in later or TODO as in for this PR?
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Oops, no this is just "TODO alex fix this before making a PR" which I pretty consistently always forget to do...
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Under a position-independent dynamic library build, an intrinsic that is
only address-taken (stored in the StreamVtable/FutureVtable, never called
by name) is lowered by LLVM to a GOT.func global keyed by its mangled Rust
symbol, and the canonical (module, field) wasm import is dropped. The
component linker resolves GOT.func slots against library exports, but no
library exports that mangled symbol and the canonical name is gone, so
components using dynamic libraries fail to link.
Emit a local wrapper for each of the intrinsics on wasm and store the
wrapper's address in the vtable. The wrapper calls the canonical import
by name (keeping the import live) and the address-take becomes an
ordinary table relocation against a defined function, which the linker
resolves.