ermler
commented
2 months ago @yamt a good question. we looked at "try-catch.wast" that was present when implementing. The files shows a test, where a tag is imported from a module and the catch-block aims at tagindex after importing.
See, how "test.throw" in external module throws "test.e0" https://github.com/WebAssembly/exception-handling/blob/cfe863826484d7d8a630324f1839f7ed3afaffc9/test/core/try_catch.wast#L5
Module imports "test.e0" as "imported-e0" https://github.com/WebAssembly/exception-handling/blob/cfe863826484d7d8a630324f1839f7ed3afaffc9/test/core/try_catch.wast#L11
and the testcase "catch-imported" calls "test.throw" and catches the "test.e0" exception as tagindex "imported-e0": https://github.com/WebAssembly/exception-handling/blob/cfe863826484d7d8a630324f1839f7ed3afaffc9/test/core/try_catch.wast#L136
we did our implementation to behave like this and wrote wamr code that looks up and replaces tagindex after returning from the external call. https://github.com/bytecodealliance/wasm-micro-runtime/blob/e8c2952bf959f6df81972fc469a4357f04ee629a/core/iwasm/interpreter/wasm_interp_classic.c#L6488
but anyhow, it is a good question, which behavior is expected, if the same tag is imported twice and so has multiple catchblocks in the importing module....
yamt
the current logic decides exception matching (ie. which catch clause to use) by comparing tag indexes. it seems wrong because, if i read the spec correctly, it's allowed for a module to import the same tag multiple times.