microg/GmsCore · info · RuntimeException

Unsupported encoding UTF8. This should always be supported.

Error message

Unsupported encoding UTF8. This should always be supported.

What it means

readStringAndClose converts the read bytes to a String via bos.toString("UTF-8") and wraps the impossible-in-practice UnsupportedEncodingException in this RuntimeException. On any compliant Java/Android runtime UTF-8 is guaranteed, so this is effectively an internal invariant violation and almost never the real problem when license reading fails.

Source

Thrown at play-services-oss-licenses/src/main/java/org/microg/gms/oss/licenses/LicenseUtil.java:101

    }

    private static String readStringAndClose(InputStream is, int bytesToRead) {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        try {
            byte[] bytes = new byte[1024];
            int read;
            while (bytesToRead > 0 && (read = is.read(bytes, 0, Math.min(bytes.length, bytesToRead))) != -1) {
                bos.write(bytes, 0, read);
                bytesToRead -= read;
            }
            is.close();
        } catch (IOException e) {
            throw new RuntimeException("Failed to read license or metadata", e);
        }
        try {
            return bos.toString("UTF-8");
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException("Unsupported encoding UTF8. This should always be supported.", e);
        }
    }
}

View on GitHub (pinned to 157c9d86ac)

Solutions

Ignore for practical debugging — investigate the sibling 'Failed to read license or metadata' IOException instead
If ever seen, verify the runtime/JVM actually supports standard charsets (Charset.isSupported("UTF-8"))
Optionally replace with StandardCharsets.UTF_8 / bos.toString(StandardCharsets.UTF_8) (API 19+) to eliminate the checked exception

Example fix

// before
return bos.toString("UTF-8");
// after
return new String(bos.toByteArray(), StandardCharsets.UTF_8); // no UnsupportedEncodingException path

Defensive patterns

Strategy: try-catch

Try / catch

try {
    text = LicenseUtil.getLicenseText(context, license);
} catch (RuntimeException e) {
    // effectively unreachable unless the JVM lacks UTF-8; log and use fallback
    Log.e("Licenses", "Unexpected charset failure", e);
    text = null;
}

Prevention

Treat this as an internal invariant; debug the IOException-based messages instead
Run on standard Android/JVM runtimes where UTF-8 is guaranteed
Optionally migrate code to StandardCharsets.UTF_8 to remove the encoding failure path entirely

When it happens

Trigger: Only when the runtime's charset infrastructure is broken or a non-standard JVM without UTF-8 support is used; never triggered by input data or license content.

Common situations: Essentially never in production; seen only on severely broken/custom runtimes. Usually a red herring when debugging license errors.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of microg/GmsCore@157c9d86ac (2026-09-06). Data as JSON: /api/errors/17925c2a89d1d9c9. Report an issue: GitHub.