CODEWITHSUNDEEP
c++templatesmacrosfunction-pointers
Marek Krzeminski
Marek Krzeminski

Reputation: 1398

Get function pointer's function name using macro # not working

I have a helper class defined like this:

DataGuard.h

template<typename T, typename D>
class DataGuard {
public:
  typedef MY_STATUS( *FunctionType )( const T*, D* );

private:
  bool               _isSuccess;
  D&                 _data;
  const FunctionType _function;

public:
  explicit DataGuard( D& data, FunctionType& function, const T* ptr );
  ~DataGuard();
  bool isSuccess() const;
};
#define DATAGUARD( Type ) const DataGuard<Type, Type##Data>

#include "DataGuard.inl"

DataGuard.inl

#define GET_FUNCTION_NAME( functionName ) #functionName

template<typename T, typename D>
DataGuard<T,D>::DataGuard( D& data, FunctionType& function, const T* ptr ) :
  _data( data ),
  _function( function )
{
  auto iReturn = function( ptr, &data );
  _isSuccess = iReturn == MY_SUCCESS;
  if( !_isSuccess ) {
    Utility::logErrorMessage( GET_FUNCTION_NAME( _function ), iReturn );  
  }
}

template<typename T, typename D>
DataGuard<T,D>::~DataGuard() {
  if( _isSuccess ) {
    _function( NULL, &_data );
  }
}

template<typename T, typename D>
bool DataGuard<T,D>::isSuccess() const {
  return _isSuccess;
}

This helper class is being called like this:

DATAGUARD( MyObject ) guard( data, MyObjectGet, ptr );

The problem is that if there is an error in the DataGuard constructor, the error message that I print is showing _function rather than the desired MyObjectGet function name.

Any ideas why the GET_FUNCTION_NAME macro is failing me?

Upvotes: 1

Views: 196

Answers (1)

Loki Astari
Loki Astari

Reputation: 264471

You can't do it from the inside the function.

You can do externally:

DATAGUARD( MyObject ) guard( data, MyObjectGet, ptr );

I would change this:

#define  DG(data, func, ptr)     data, func, ptr, #func

// usage is now:
DATAGUARD( MyObject )  guard(DG(guard, data, MyObjectGet, ptr));

You will notice that we pass the function pointer and the name of the function pointer as a quoted string as the last parameter. You can use this string as part of your error message.

Upvotes: 1

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