1907222_truncate_error.html

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    <meta charset="utf-8" />

    <script src="/tests/SimpleTest/SimpleTest.js"></script>

    <link rel="stylesheet" href="/tests/SimpleTest/test.css" />

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    <script>

      // Ensure that, when WebGPU generates an error message that is later

      // truncated by `wgpu_bindings::error::ErrorBuffer::init`, that

      // truncation always produces valid UTF-8, even when the error contains

      // multi-byte encodings.

      async function truncate_error_messages() {

        // The specific error we'll try to provoke is submitting a command

        // buffer to the wrong device's queue.

        const adapter = await navigator.gpu.requestAdapter();

        const device1 = await adapter.requestDevice();

        const device2 = await adapter.requestDevice();

        // Try a range of label lengths (578±200, where 578 is the length that

        // tickles the original bug), searching for one that, when combined with

        // the error message and then truncated at whatever error message byte

        // length limit Firefox is imposing, will produce invalid UTF-8.

//

        // Use a label containing n space characters followed by a crab emoji,

        // U+1F980, which requires four bytes to encode in UTF-8. Since this has

        // a four-byte encoding at the end, we only need to try every third

        // length to ensure we will always try a truncation point in the midst

        // of that encoding.

        for (let len = 378; len < 778; len += 3) {

          const label = ' '.repeat(len) + '\uD83E\uDD80';

          const encoder = device1.createCommandEncoder({ label });

          const command_buffer = encoder.finish();

          // We don't want an error scope around this, because what makes

          // Firefox notice the bad UTF-8 is attempting to log the uncaught

          // WebGPU error as a warning.

          device2.queue.submit([command_buffer]);

      truncate_error_messages()

        .catch(e => {

          console.log(e);

})

        .finally(() => {

          // End the crashtest.

          document.documentElement.removeAttribute("class");

});

    </script>

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