Array, pointer, malloc

[EirikO]

I whant to have a array like this:

Msg[0] = 436;
Msg[1] = 4;

The values are stored in another array. My code are like this:

#include <stdio.h>
#include <stdlib.h>

void main()
{
int DP[2];
//DP = malloc(2*sizeof(int));
char *Msg;
Msg = malloc(2*sizeof(int));

DP[0] = 436;
DP[1] = 3;

sprintf(&Msg[0],"%d",DP[0]);
sprintf(&Msg[1],"%d",DP[1]);

printf("%d\n",Msg[0]);
printf("%d\n",Msg[1]);
}

It output 51 and 53...

[vart]

1. int main()

2.

int DP[2] = {436,3};

3. sprintf expects as a first parameter char* - pointer to the buffer where the string will be stored

If you want to create the string like "436 3" - you should allocate enough space (sizeof int has nothing to do with the number of bytes required to represent the int as a string)

And you will use sprintf as
sprintf(Msg,"%d %d",DP[0], DP[1]);

4. to print the char buffer you will use

printf("%s\n",Msg);

[foxman]

You should also free the memory allocated by malloc() before quitting the program:

free(Msg);

And could also add

return 0;

to the end of your main function.


Oh, and you say

I whant to have a array like this:

Msg[0] = 436;
Msg[1] = 4;

well... since you declare Msg as a char array, you won't be able to have such thing since a char can hold only one character.
One way to solve this is using a 2D array, like

...
char *Msg[2];
msg[0] = (char *) malloc(...);
msg[1] = (char *) malloc(...);

sprintf(msg[0], "%d", 436);
sprintf(msg[1], "%d", 4);
...

but it's an "overcomplex" solution for this kind of problem, knowing you could do someting like

char Msg[][15] = {"436", "4"};

[mike_g]

And could also add
Code:

return 0;

At the moment main could not even return a value as its declared void. Also I'm pretty sure that Int main() returns 0 by default.

[robatino]

> Also I'm pretty sure that Int main() returns 0 by default.
It does in C99 and C++, but not in C90 (I think that in C90, without the explicit return, the return value is undefined). So in C at least, to be compatible both with the more commonly used C90 and the newer C99, it's a good idea to use an explicit return.

[Salem]

Where does C99 state that?

[robatino]

> Where does C99 state that?
I don't know offhand, but it's in the FAQ:

http://faq.cprogramming.com/cgi-bin/...&id=1043284376

which BTW is off slightly since it claims that in C89/90 the explicit return is required - it's not actually required for C90 compliance, just to have a well-defined return value (which of course is a good enough reason to include it).

Edit:

http://c0x.coding-guidelines.com/5.1.2.2.3.html