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Missing validation error #8785
Description
See jj.tar.gz.
Unpack via:
% tar xvzf jj.tar.gz
...
When running with V8 we get a validation error:
% d8 $PWD/pkg/dart2wasm/bin/run_wasm.js -- $PWD/jj.mjs $PWD/jj.wasm
run_wasm.js:346: CompileError: WebAssembly.compile(): Compiling function #181:"main" failed: not enough arguments on the stack for drop (need 1, got 0) @+25996
}
^
CompileError: WebAssembly.compile(): Compiling function #181:"main" failed: not enough arguments on the stack for drop (need 1, got 0) @+25996
1 pending unhandled Promise rejection(s) detected.
Though optimizing with wasm-opt works fine and the result runs:
% wasm-opt --enable-gc --enable-reference-types --enable-multivalue --enable-exception-handling --enable-nontrapping-float-to-int --enable-sign-ext --enable-bulk-memory --enable-threads --enable-simd '--no-inline=*<noInline>*' --traps-never-happen -g -Os --gufa -Os -Os jj.wasm -o jj.wasm
% d8 $PWD/pkg/dart2wasm/bin/run_wasm.js -- $PWD/jj.mjs $PWD/jj.wasm
%
Is wasm-opt not supposed to issue a validation error here as well? (even though the corresponding code is unreachable)
local.get $reporter
drop
drop
block $label2
unreachable
end
drop
Activity
tlively commentedon May 28, 2026
This is WAI for now, unfortunately. Binaryen represents that block as having bottom type internally, so this parses into valid Binaryen IR, even though it is not valid WebAssembly. A fix would involve adding an entirely new validator in the parser, since the IR does not retain enough information to detect this error.
Fix WebAssembly#8785: validate Wasm stack in IRBuilder without changi…