Thread: function overloading in C

Function overloading:

void myfun( int );
void myfun( float );
void myfun( char * );
void myfun( struct myObject * );

That's function overloading.

Code:

void somefun( something_here )
{
    anotherfun( something_here ):
}

/*or*/
#define somefunction somefun
somefuction( x );

Neither of those are overloading. One is basicly creating a ... what's the term I'm looking for ... an interface to use another function, and the second is just defining some other word to call a single function.

"Overloading" is when you have more than one function with the same exact name that takes varried arguments combine with, optionally, different return types.

C does not, as stated numerous times, support overloading.

Quzah.

Yes, they have to have different arguments or else it's not overloading.

They are probably using a macro or something to avoid having errors with redefinitions. Check out the header or point me to where I can download it and I'll be able to tell you exactly what it's doing.

Originally posted by rotis23
>>With function overloading you still have to write all the functions though, you just have them all the same name.

by this definition, dmalloc overloads the malloc and free functions in c

no, it replaces it; once you have #include'd dmalloc you cannot call the original gangster malloc()

Originally posted by rotis23
ok, its not overloading.

i was just making the point that you can define funtions in c that are defined elsewhere in included libraries using the same name.

You can have more than one function with the same name in a program. They just can't be allowed to see eachother. Otherwise you'll get a compiler error. Example:

File1

Code:

#include <stdio.h>
static void myfun( void )
{
    printf("File1:myfun( ) is called.\n");
}
void callfun1( void )
{
    myfun( );
}

File2

Code:

#include <stdio.h>
static void myfun( void )
{
    printf("File2:myfun( ) is called.\n");
}
void callfun2( void )
{
    myfun( );
}

File3

Code:

#include "myheader1.h"
#include "myheader2.h"
int main( void )
{
    callfun1( );
    callfun2( );
    return 0;  
}

Compile each file seperately, in order. This assumes you have a header file for each of the others that basicly just prototypes the call function. Link and run.

You can have different files in different modules with the same name. You just have to hide them from eachother so you don't have a problem.

Originally posted by rotis23
please bear in mind that i have been in the middle of a polystyrene fight throughout this dialog.

Did you win?

Quzah.

C does not support function overloading.
Variant arguments are not the same thing with function overloading. Have you ever seen something like...

Code:

#include <stdarg.h>

float avg(char *start,...)
{
	int sum=0,n=0,arg;
	va_list ap;
	for (va_start(ap,start);arg=va_arg(ap,int);n++)
		sum+=arg;
	va_end(ap);
	return (float)sum/n;
}

this function needs any numbers of arguments but we must expect type of the first argument to be char* and next arguments to be int (not float nor double, etc). You can not redefine this function to accept additional types. Hence it does not support function overloading.