[C++] Incorrect computeEncodedLength() generated for VarData member - uses sizeof(null) instead of sizeof(char)

[spanti]

Description

When generating the C++ codec for UtxErrorDto (and other messages containing varData fields), the generated method computeEncodedLength() contains incorrect size calculations. Specifically, the generator emits:

encodedLength += m_identity.size() * sizeof(null);

However, null is not a valid type and results in incorrect encoded length calculation. Replacing sizeof(null) with sizeof(char) fixes the issue.

Generated Code (Incorrect)

std::size_t computeEncodedLength() const
{
    std::size_t encodedLength = 0;
    encodedLength += UtxLoginCommand::sbeBlockLength();

    encodedLength += UtxLoginCommand::identityHeaderLength();
    encodedLength += m_identity.size() * sizeof(null);

    encodedLength += UtxLoginCommand::credentialHeaderLength();
    encodedLength += m_credential.size() * sizeof(null);

    encodedLength += UtxLoginCommand::collectedDataHeaderLength();
    encodedLength += m_collectedData.size() * sizeof(null);

    return encodedLength;
}

Corrected Code (Works as expected)

std::size_t computeEncodedLength() const
{
    std::size_t encodedLength = 0;
    encodedLength += UtxLoginCommand::sbeBlockLength();

    encodedLength += UtxLoginCommand::identityHeaderLength();
    encodedLength += m_identity.size() * sizeof(char);

    encodedLength += UtxLoginCommand::credentialHeaderLength();
    encodedLength += m_credential.size() * sizeof(char);

    encodedLength += UtxLoginCommand::collectedDataHeaderLength();
    encodedLength += m_collectedData.size() * sizeof(char);

    return encodedLength;
}

Expected Behavior

The generator should use:

sizeof(char)

for all varData fields, since they are encoded as byte arrays.

Actual Behavior

The generator outputs:

sizeof(null)

which is invalid and results in incorrect encoded length calculation.

Steps to Reproduce

Define a message containing <data type="varData">

Generate C++ codecs

Inspect the generated computeEncodedLength() method

Observe that sizeof(null) is emitted instead of sizeof(char)