wierd pointer behavior

[mIXpRo]

hi ,
i wrote this function :

PlayerResult playerGetInstruments(Player player, Instrument** instruments,
		int* amount) {
	if (player == NULL || amount == NULL ) {
		return PLAYER_NULL_ARG;
	}
	int indexLast = 0;
	indexLast = getInstrumentsCount(player);
	if(indexLast <=0){
		return PLAYER_INSTRUMENT_AMOUNT_ERR;
	}
	if(*instruments!= NULL){
		free(*instruments);
	}
	(*instruments) = (Instrument*) malloc(sizeof(Instrument*) * indexLast);
	if ((*instruments) == NULL ) {
		return PLAYER_MEMORY_ERR;
	}
	PlayerResult result;
	if (!playerIsLegal(player, &result)) {
		free((*instruments));
		return result;
	}
	for (int i = 0; i < indexLast; i++) {
		instruments[i] = (Instrument*)malloc(sizeof(struct instrument_t));
		strcpy((*instruments[i]).name,player->instruments[i].name);
		strcpy((*instruments[i]).profession,player->instruments[i].profession);
	}
	*amount = indexLast;
	return PLAYER_SUCCESS;
}

and i tried testing it with this :

Player player=playerCreate("Nadav", "Peled", 2);
	Instrument* instruments, inst, inst2;
	instruments = NULL;
	int amount;
	strcpy(inst.name, "guitar");
	strcpy(inst.profession, "guitarist");
	strcpy(inst2.name, "bass");
	strcpy(inst2.profession, "bassist");
	PlayerResult res=playerAddInstrument(player, inst);
	res=playerAddInstrument(player, inst2);


	//Chcking func with legal inputs
	res=playerGetInstruments(player, &instruments, &amount);
	ASSERT(res==PLAYER_SUCCESS);
	ASSERT(amount==2);
	ASSERT((strcmp(instruments[0].name, inst.name)==0) &&
			(strcmp(instruments[1].name, inst2.name)==0));

my problem is when running in eclipse until the line
return PLAYER_SUCCESS

the stack seems ok meaning

instruments[0].name = "guitar"
instruments[0].profession = "guitarist"
instruments[1].name = "bass"
instruments[1].profession = "bassist"

but when i return to the testing function (the second above)
i get in stack

instruments[0].name = "guitar"
instruments[0].profession = "guitarist"
instruments[1].name = "i\0\0\0\0bass"
instruments[1].profession = "\0\0\0\0bassist"

and i tried adding more instruments then i got :

instruments[2].name = "\0\0\0\0i\0\0\0\0XXXX"
instruments[2].profession = "\0\0\0\0\0\0\0\0XXXXXX"

its like it's adding every time 4 bytes
why is that ???

thnx

[kbw]

That seems a little confused to me.

In:

PlayerResult playerGetInstruments(Player player, Instrument** instruments, int* amount)

you should think of instruments as a pointer passed by reference.

With that in mind, this is a reasonable statement:

(*instruments) = (Instrument*) malloc(sizeof(Instrument*) * indexLast);

but this isn't:

	for (int i = 0; i < indexLast; i++) {
		instruments[i] = (Instrument*)malloc(sizeof(struct instrument_t));
		strcpy((*instruments[i]).name,player->instruments[i].name);
		strcpy((*instruments[i]).profession,player->instruments[i].profession);
	}

Also, don't use malloc in C++ unless there's a specific good reason to.

[mIXpRo]

can you please explain what do you mean by unreasonable statement .

[kbw]

You're treating it as an array of Instrument*, which it clearly isn't.