Predefined function parameter giving problems.

RHLinuxGUY · 01-31-2007, 07:29 PM

Hello, I got a problem with with my header file.

It has an external reference to a function, which that function has a parameter that is predefined.

Here is the neccessary information the source file has (.cpp) followed by the header file (.h):

Source:

Code:

//...

int function(/*...*/, int number);

//...

int function(/*...*/, int number = 0)
{
    //...
}

//...

Header:

Code:

//...

extern int function(/*...*/, int number = 0);

//...

Here is the error I recieve when I compile my program:

Code:

g++ -c p_datamanip.cpp p_error.h -g -W -Wall -ansi -pedantic `sdl-config --cflags --libs` -lSDL
p_datamanip.cpp: In function `int p_fileread_quote(std::string, std::string, std::string&, unsigned int)':
p_datamanip.cpp:115: error: default argument given for parameter 4 of `int p_fileread_quote(std::string, std::string, std::string&, unsigned int)'
p_datamanip.cpp:23: error: after previous specification in `int p_fileread_quote(std::string, std::string, std::string&, unsigned int)'
make: *** [p_datamanip.o] Error 1

What should I do?

graemef · 01-31-2007, 10:36 PM

If I understand what you have done correctly, the compiler can't tell the difference between the two functions. To overload a function the parameter list must differ in the number of parameters or in the type order.

So the following would be valid:

int fn (string name);
int fn (string name , int id); // different number
int fn (int id, string name); // different order

What you can't do is to just change the return type, the name of the parameter or add a default value

So the following would be invalid (assuming that the above three have been defined):

void fn (string); // change in return type not valid
int fn (string name, int amount); // change parameter name not valid
int fn (string name , int id=0); // add a default value not valid

What can you do?

If it is just a case of a default value and the logic is the same then replace the function signature that doesn't have a default value with one that does.

If it is truly performing some different logic then give it a different name

If it is a case when it wants some different data but performs the same logic then you could add an intermediate function to make that clear, but this new function will use the original function.

I'm sure there are many other alternatives but without more understanding of the problem at hand...