Truncated JSON output from emscripten binary with viaIR: true and both ir and * selected as outputs

[cameel]

The snippet from #14361 has one more weird effect that looks unrelated to that issue. When I select * output together with ir, enable viaIR and pass it to the emscripten binary, the produced JSON is truncated.

It only happens when these outputs are both selected at the same time. Changing the snippet to something simple like contract {} resolves the problem as well so it's something in the code that triggers it. Unlike in #14361, this happens both with and without optimizer.

It's possible that solc-js crashes in the process, but there's nothing in the output that would indicate that (no Killed or core dumped on the console). The fact that it always cuts off at the same point would also indicate that it's the JSON generation that suddenly decides to stop for whatever reason, but then successfully outputs that unfinished content.

Environment

Tested with solc-js 0.8.20 with the binary included in the release.

Repro

input.json

{
    "language": "Solidity",
    "sources": {
        "A": {"content": "
            contract C {
                function f2() public {
                    bytes1[2] memory k;
                    k[0] = bytes1(0);
                }
            }"
        }
    },
    "settings": {
        "viaIR": true,
        "outputSelection": {
            "*": {"*": ["ir", "*"]}
        }
    }
}

Script

npm install solc
emscripten_output=$(cat input.json | npx --no -- solcjs --standard-json)
echo "$emscripten_output"
echo "$emscripten_output" | jq

Output

The output from jq is:

parse error: Unfinished string at EOF at line 2, column 0

which means that the produced JSON is malformed. And indeed, this is how it ends:

}\n\n            function write_to_memory_t_bytes1(memPtr, value) {\n                mstore(memPtr, cleanup_t_bytes1(value))\

This is the content of the ir field, which is not terminated. The Standard JSON output just ends abruptly in the middle of it.