function overloading problems (not working sometimes)

Posted By: sivan

function overloading problems (not working sometimes) - 05/06/15 14:22

hi

I have a little problem when using function overloading:
when passing different types of pointers as parametrs, sometimes the one with char* is used instead of the one with short*, sometimes the one with var* is used instead of the one with int*, even if the type of other parameters differ. here are the little examples:

here char* is used instead of short* (originally both bytevalue were char, but it is wrong with char and short too)

Code:

void		array_fillbytes(char* arrayin, int arraylength, char bytevalue)
{
	if (!arrayin)					return;
	if (arraylength <= 0)		return;
	
	memset(arrayin, bytevalue, sizeof(char) * arraylength);
}


void		array_fillbytes(short* arrayin, int arraylength, short bytevalue)
{
	if (!arrayin)					return;
	if (arraylength <= 0)		return;
	
	memset(arrayin, (char)bytevalue, sizeof(short) * arraylength);
}

it does not work properly even if I add an int or var fake parameters respectively in the end, always the one with var* is used:

Code:

void	ShowArrayElements(int* inarray, int arraylength, var posx, var posy)
{
	if (!inarray) return;
	
	int i;
	for (i=0; i<arraylength; ++i)
		{
			draw_text( str_for_int(NULL, inarray[i]), posx, posy + i*20, COLOR_RED );
		}
}


void	ShowArrayElements(var* inarray, int arraylength, var posx, var posy)
{
	if (!inarray) return;
	
	int i;
	for (i=0; i<arraylength; ++i)
		{
			draw_text( str_for_num(NULL, inarray[i]), posx, posy + i*20, COLOR_GREEN );
		}
}

in this case only char* is used instead of the short*, all others are fine:

Code:

void		array_fill(char* arrayin, int arraylength, char elementvalue);										
void		array_fill(short* arrayin, int arraylength, short elementvalue);
void		array_fill(int* arrayin, int arraylength, int elementvalue);
void		array_fill(var* arrayin, int arraylength, var elementvalue);
void		array_fill(VECTOR* arrayin, int arraylength, VECTOR* elementvalue);

do I do something totally wrong, or the lite-c compiler is playing with me?

I can make workarounds of course, I just want to get more, more, and more knowledge (or engine bugs)

Posted By: WretchedSid

Re: function overloading problems (not working sometimes) - 05/06/15 14:52

I would say the type deduction is failing you there. But why rely on that anyway, you may end up with wrong pointer types anyway. A better solution would be this:

Code:

void array_fill(void *arrayin, int arraylength, char elementvaluem int elementSize);
{
	if(!arrayin || arraylength <= 0) 
		return;
	
	memset(arrayin, bytevalue, elementSize * arraylength);
}

(You indentation is seriously trippy though. You may want to adopt indentation with tabs and alignment with spaces in the future so it looks universally consistent)

Posted By: Wjbender

Re: function overloading problems (not working sometimes) - 05/06/15 14:54

i like to use one of two methods ,even in c++ even though i dont have to , and to accomplish
both , i use char* instead of adding more code for types or whatever.

method 1: i pack all functions in to one

Code:

//in lite-c i used such a similir function
void place_entity(ENTITY* my_ent,char* my_type)
{
	if(str_cmp(my_type,"a big rock"))
	{
	}
	if(str_cmp(my_type,"a small rock"))
	{
	}
	if(str_cmp(my_type,"a tree"))
	{
	}
}
...
place_entity(me,"a big rock");
place_entity(me,"a tree");

and method 2: a dispatcher function , it dispatches other functions

Code:

//in c++ i used this for a thread dispatcher ,same concept
void thread_dispatcher(const char* task,void* task_packet,void* second_task_packet)
{
	if(m_navbuilder)
	{
		if(strcmp(task,"build the navmesh")==0)
		{
			custombuild* build_settings=(custombuild*)task_packet;
			m_navbuilder->Nav_From_Custombuild(build_settings);
		}
		if(strcmp(task,"load the navmesh")==0)
		{
			char* filename=(char*)task_packet;
			m_navbuilder->load_all_tiles((char*)filename);
		}
		if(strcmp(task,"save the navmesh")==0)
		{
			char* filename=(char*)task_packet;
			m_navbuilder->save_all_tiles((char*)filename);
		}
		if(strcmp(task,"build all tiles")==0)
		{
			m_navbuilder->build_all_tiles();
		}
		if(strcmp(task,"add single tile")==0)
		{
			VECTOR* pos=(VECTOR*)task_packet;
			m_navbuilder->build_tile(pos);
		}
		if(strcmp(task,"build tiles in bounds")==0)
		{
			VECTOR* min=(VECTOR*)task_packet;
			VECTOR* max=(VECTOR*)second_task_packet;
			m_navbuilder->build_tiles_box(min,max);
		}
	}
}

//////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////
//************************************
// BUILD A NAVMESH
//
DLLFUNC void* nav_build(custombuild* build_settings)
{
	thread_function *thread_func=new thread_function(thread_dispatcher,"build the navmesh",(custombuild*)build_settings,(int*)NULL);
	if(thread_func->is_alive()) return (thread_function *) thread_func;
	delete thread_func;
	return NULL;
}

you can easily convert to the type you need
like

Code:

void bla(char* type ,void* arg1,void* arg2,void* arg3)
{
	if(str_cmp(type,"a string"))
	{
		STRING* this_string=(STRING*)arg1;
		if(this_string)
		{
			...
		}
	}
	if(str_cmp(type,"an integer"))
	{
		int* this_integer=(int*)arg1;
		if(this_integer)
		{
			...
		}
	}
	if(str_cmp(type,"an integer with size"))
	{
		int* this_integer=(int*)arg1;
		int* this_size=(int*)arg2;
		if(this_integer && this_size>-1)
		{
			...
		}
	}
}

bla("a string",(STRING*)mystring,(int*)NULL,(int*)NULL);
//or
bla("a string",(STRING*)mystring,NULL,NULL);
bla("an integer",(int*)myinteger,......
bla("an integer with size",(int*)myinteger,(int*)my_size,NULL);

edit ah wait sid is on it

Posted By: WretchedSid

Re: function overloading problems (not working sometimes) - 05/06/15 15:07

Speaking of though, not wanting to rain into your parade and I know you put some good effort into your array tools... But. What about something that is a tad more user friendly and also provides bounds checking? I mean absolutely no offense and I'll take the code down if you want to, but here is what I mean:

Code:

typedef struct
{
	void *_buffer; // Actual data
	size_t _size; // Number of elements
	size_t _capacity; // Allocated number of elements
	size_t _elementSize; // Element size
} array_t;

array_t *array_create(size_t elementSize)
{
	array_t *array = malloc(sizeof(array_t));
	array->_elementSize = elementSize;
	array->_size = 0;
	array->_capacity = 5; // start out with 5 elements. Tweak if desired. This just makes the life easier since there is always a buffer and we don't have to care about cases where it's NULL
	array->_buffer = malloc(array->_capacity * array->_elementSize);

	return array;
}
void array_delete(array_t *array)
{
	free(array->_buffer);
	free(array);
}

void __array_assert_size(array_t *array, size_t required) // Makes sure that the array fits
{
	size_t toCopy = array->_size;
	if(toCopy > size)
		toCopy = size;

	if(required > array->_capacity)
	{
		size_t nextCapacity = array->_capacity * 1.5; // Gives a nice grow curve. Alternatively doubling also works, gets messy with large arrays though
		if(nextCapacity < required)
			nextCapacity = required;

		void *buffer = malloc(nextCapacity * array->_elementSize); // TODO: Handle errors
		memcpy(buffer, array->_buffer, toCopy * array->_elementSize);
		free(array->_buffer);

		array->_buffer = buffer;
		array->_capacity = nextCapacity;
	}
	else
	{
		size_t nextCapacity = array->_capacity >> 1;
		if(nextCapacity >= required && nextCapacity > 5) // Keep at least space for 5 elements
		{
			void *buffer = malloc(nextCapacity * array->_elementSize); // TODO: Handle errors
			memcpy(buffer, array->_buffer, toCopy * array->_elementSize);
			free(array->_buffer);

			array->_buffer = buffer;
			array->_capacity = nextCapacity;
		}
	}
}


void array_copyin_data(array_t *array, void *data, size_t elements)
{
	__array_assert_size(array, array->_size + elements);
	memcpy(((char *)array->_buffer) + array->_size * array->_elementSize, data, elements * array->_elementSize);
	array->_size += elements;
}
void array_copyout_data(array_t *array, void *data, size_t start, size_t elements)
{
	if(start + elements >= array->_size)
	{
		printf("Trying to access elements [%d, %d) in array with only %d elements", start, start + elements, array->_size);
		return;
	}

	memcpy((data, (char *)array->_buffer) + start * array->_elementSize, elements * array->_elementSize);
}

// Alternatively, you can also work with single elements at a time... Something like this:
void array_add_object(array_t *array, void *object)
{
	__array_assert_size(array, array->_size + 1);
	memcpy(((char *)array->_buffer) + array->_size * array->_elementSize, data, array->_elementSize);
	array->_size ++;
}

I'll leave implementing other operations as exercise for anyone who wants to use something like this. It's merely to show the general idea anyway.
Also, whipped up in like 10 minutes and didn't test it, so there might be syntax errors. I tried putting down some comments to make clear what the intend is.

Edit: Fixed errernous usage of _size vs. _capacity.
Edit 2: More edits

Posted By: sivan

Re: function overloading problems (not working sometimes) - 05/07/15 07:26

thanks both of you.

as I said I can make workarounds, e.g. I use mainly for filling an array with bytes something similar to what Sid wrote in your 1st post. the type branching was my another idea to fix overloading problems, or using _char/_short/... ending at function names is also fine.

I also wanted to make something similar to the one utilizing a struct to store necessary array information, but my more basic solution currently satisfies my needs and easy enough to be used by beginners, and not planned to spend too much time with it. I just really need array rotation and element addition, which works fine.

basically, I just have not understood the strange overloading phenomena...

Posted By: Wjbender

Re: function overloading problems (not working sometimes) - 05/09/15 09:24

it isn't that it is an anomaly , just normal for the c type language /compilers I believe.

http://stackoverflow.com/questions/479207/function-overloading-in-c

Posted By: sivan

Re: function overloading problems (not working sometimes) - 05/10/15 09:33

thanks, this is what I needed