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Compiling with debuginfo causes incorrect output on wasm32-unknown-unknown target #46339

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Herschel opened this issue Nov 28, 2017 · 2 comments
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Compiling with debuginfo causes incorrect output on wasm32-unknown-unknown target #46339

Herschel opened this issue Nov 28, 2017 · 2 comments
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A-debuginfo Area: Debugging information in compiled programs (DWARF, PDB, etc.) C-bug Category: This is a bug. O-wasm Target: WASM (WebAssembly), http://webassembly.org/

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@Herschel
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Herschel commented Nov 28, 2017 •
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The following example will incorrectly return 1 instead of 10 when compiling with the wasm32-unknown-unknown target and -C debuginfo=2:

fn add_one(i: i32) -> i32 {
	i + 1
}

#[no_mangle]
pub fn run() -> i32 {
	add_one(9)
}

HTML:

<!DOCTYPE html>

<html>
	<head>
		<title>Test</title>
		<script>
			fetch('lib.wasm')
				.then(response => response.arrayBuffer())
				.then(bytes => WebAssembly.instantiate(bytes, {
					'env': {}
				}))
				.then(results => {
				    console.log(results.instance.exports.run());
				});
		</script>
	</head>
	<body>
	</body>
</html>

rustc command:

rustc lib.rs --crate-type cdylib --target wasm32-unknown-unknown -C debuginfo=2

Removing -C debuginfo=2 gives the correct output

rustc version:
rustc 1.24.0-nightly (560a5da9f 2017-11-27)
@kennytm kennytm added A-debuginfo Area: Debugging information in compiled programs (DWARF, PDB, etc.) C-bug Category: This is a bug. O-wasm Target: WASM (WebAssembly), http://webassembly.org/ labels Nov 28, 2017
@alexcrichton
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This looks to be an LLVM bug fixed in LLVM 5, the upgrade to which is tracked by #43370

@alexcrichton
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Upon more recent testing I believe this isn't actually fixed in LLVM 5 (an LLVM assertion still trips). To help consolidate though I'm going to close this in favor of #46367 which I believe is the same issue.

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A-debuginfo Area: Debugging information in compiled programs (DWARF, PDB, etc.) C-bug Category: This is a bug. O-wasm Target: WASM (WebAssembly), http://webassembly.org/
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