Engine: Using g++10 Compiler Optimizations breaks Engine

[mrzzy]

Problem

Turning on O2 compiler optimizations (via CMAKE_BUILD_TYPE=Release) produces a Engine that builds successfully, but crashes on startup:

terminate called after throwing an instance of 'std::runtime_error'
  what():  Invalid protobuf type.

Investigation

Debugger

Hooking up the Engine to a Debugger (LLDB) produces the following backtrace:

  * frame #6: 0x00005555555b849f bentobox`ics::component::UserComponent::setValue(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, bento::protos::Value const&) (.cold) at userValue.h:81:5
    frame #7: 0x00005555555db6d4 bentobox`main at main.cpp:63:18

From the backtrace, the issue seems to stem from:

auto tex1 = ics::component::Texture2DComponent();
auto value = bento::protos::Value();
value.mutable_primitive()->set_int_64(1);
value.mutable_data_type()->set_primitive(
    bento::protos::Type_Primitive_INT64);
tex1.setValue("texture", value);  // Crash happens here

isProtoTypeOfType() is called in setValue():

    // TODO(joeltio): Streamline this together with eqOp
    // If schemaType and value are numeric, try to convert
    if (proto::isProtoTypeOfTypes<proto_NUMERIC>(schemaType) && // Crash happens here
        proto::isValOfTypes<proto_NUMERIC>(value)) {
        proto::runFnWithVal<proto_NUMERIC>(
            value, [&valToSet, &schemaType]<class X>(X x) {

Resulting in a crash in isProtoTypeOfType():

template <class T>
requires ProtobufType<T> bool isProtoTypeOfType(
    const bento::protos::Type& protoType) {
    throw std::runtime_error("Invalid protobuf type.");
}

Templating

isProtoTypeOfType() is template function that is implemented for:

• specific types: INT32, INT64, FLOAT32, FLOAT64, STR, BOOL.
• a catchall T type with an implementation that throws the exception causing the crash.
• this function assumes the catchall implementation will be skipped if a specific types implementation with a closer matching type exists.

To verify this assumption print statements where inserted in isProtoTypeOfType():

• Without optimization, this assumption holds and the catchall implementation is never executed.
• With optimization this assumption does not hold: ALL implementations, including the catchall implementation is executed, causing the crash.

Proposed Fix

Rework isProtoTypeOfType() to remove its dependency on this assumption:

• Remove the catchall case. This should convert the error of specifying an invalid type from a runtime one to a compile time one. The compiler should fail to find a matching implementation for isProtoTypeOfType() and throw an error.