SAL versus modern C++

The following pairs of function signatures compare SAL annotated functions versus plain C++ functions. The meaning of the SAL macros can be found here. We can assume that SAL functions use the return value to indicate errors whereas the plain C++ functions throw exceptions instead.

HRESULT foo( _In_ obj * pData );
void foo( const obj & data );

HRESULT foo( _Inout_ obj * pData );
void foo( obj & data );

HRESULT foo( _Out_ obj * ppData );
obj foo();

HRESULT foo( _Outptr_ obj * * ppData );
obj & foo();

HRESULT foo( _In_opt_ obj * pData );
void foo( const obj * data );

HRESULT foo( _Inout_opt_ obj * pData );
void foo( obj * data );

HRESULT foo( _Out_opt_ obj * pData );
???

HRESULT foo( _Outptr_opt_ obj * * ppData );
obj * foo(); 

1. What would be the function signature corresponding to an _Out_opt_ parameter?

2. Would a smart compiler be able to do the same checks using the C++ signatures as the Visual Studio Code Analysis Tool does using SAL?

3. Are there other advantages? For example, void foo( const obj & data ); prolongs the lifetime of temporary objects so that the destructor is guaranteed to be called (sometime) after foo returns.