java-native-access/jna · error · RuntimeException

Unsupported empty type:

Error message

Unsupported empty type: 

What it means

When enumerating all values of a key (registryGetValues), the library handles the case where lpcbData is 0 (an empty value). For an empty value whose type is one of the known string/number kinds it returns a default empty object, and WinNT.REG_NONE maps to null; any other type with zero-length data reaches the default branch and throws this RuntimeException. It signals the value is empty AND of a type the library does not know how to represent emptily.

Source

Thrown at contrib/platform/src/com/sun/jna/platform/win32/Advapi32Util.java:2173

                    case WinNT.REG_BINARY: {
                        keyValues.put(nameString, new byte[0]);
                        break;
                    }
                    case WinNT.REG_SZ:
                    case WinNT.REG_EXPAND_SZ: {
                        keyValues.put(nameString, new char[0]);
                        break;
                    }
                    case WinNT.REG_MULTI_SZ: {
                        keyValues.put(nameString, new String[0]);
                        break;
                    }
                    case WinNT.REG_NONE: {
                        keyValues.put(nameString, null);
                        break;
                    }
                    default:
                        throw new RuntimeException("Unsupported empty type: "
                            + lpType.getValue());
                }
                continue;
            }

            switch (lpType.getValue()) {
                case WinNT.REG_QWORD: {
                    keyValues.put(nameString, byteData.getLong(0));
                    break;
                }
                case WinNT.REG_DWORD: {
                    keyValues.put(nameString, byteData.getInt(0));
                    break;
                }
                case WinNT.REG_SZ:
                case WinNT.REG_EXPAND_SZ: {
                    if (W32APITypeMapper.DEFAULT == W32APITypeMapper.UNICODE) {
                        keyValues.put(nameString, byteData.getWideString(0));

View on GitHub (pinned to d036ad9781)

Solutions

1. Catch RuntimeException per key when enumerating, log the offending value name/type, and continue with the remaining values.
2. Read only the specific values you need with typed getters instead of enumerating the whole key.
3. If you control the writer, use standard types (REG_SZ, REG_DWORD, REG_BINARY) and avoid exotic types like REG_LINK.
4. Update JNA - support for additional registry types in enumeration has improved in later releases.

Example fix

// before
TreeMap<String, Object> all = Advapi32Util.registryGetValues(root, key); // throws on exotic empty type

// after
try {
    TreeMap<String, Object> all = Advapi32Util.registryGetValues(root, key);
} catch (RuntimeException e) {
    LOG.warn("Skipping key with unsupported empty value type: {}", key, e);
}

// inspect value types before bulk enumeration
Advapi32Util.InfoKey info = Advapi32Util.registryQueryInfoKey(key, 0); // max value len/type info
// per-value type check:
// IntByReference lpType from Advapi32.INSTANCE.RegQueryValueEx(...) then compare against known types

try { return Advapi32Util.registryGetValues(key); }
catch (RuntimeException e) { log.warn("Unsupported empty value type in {}: {}", key, e.getMessage()); return Collections.emptyMap(); }

When it happens

Trigger: Calling Advapi32Util.registryGetValues(key) or registryGetValues(root, key, samDesiredExtra) on a key containing a zero-byte value whose type is not one of REG_SZ/REG_EXPAND_SZ/REG_BINARY(most types accepted)/REG_DWORD/REG_QWORD/REG_MULTI_SZ/REG_NONE - e.g. an exotic or corrupted type like REG_LINK or REG_RESOURCE_LIST with zero data.

Common situations: Enumerating driver/hardware keys (HKLM\SYSTEM\CurrentControlSet\Enum) that contain REG_RESOURCE_LIST / REG_FULL_RESOURCE_DESCRIPTOR values; keys created by third-party tools writing unusual types; corrupted registry entries.

Related errors

• Unsupported type:
• Unexpected registry type + lpType.getValue() + , expected RE
• Unexpected registry type {}, expected REG_SZ
• Unexpected registry type {}, expected REG_BINARY
• Unexpected registry type {}, expected REG_DWORD

AI-assisted analysis of java-native-access/jna@d036ad9781 (2026-09-12). Data as JSON: /api/errors/f79de720ab8f445e. Report an issue: GitHub.