malloc error under microsoft compiler

[ushtabalakh]

int *p;
p = malloc(sizeof(int));

I receive this error : error C2440: '=' : cannot convert from 'void *' to 'int *'

I'm trying to have a dynamically allocated array of integers, After doing this how can I access the third and fourth element of this array?

 

[xwb]

You must be building it as C++. You probably have the /Tp flag set somewhere. Shouldn't need to cast in C. Anyway try

p = (int*) malloc (sizeof (int));

 

[Salem]

> After doing this how can I access the third and fourth element of this array?
The given malloc call has only ONE allocated int, not 3 or 4.

As xwb noted, you need to make sure you're compiling as C (and not C++).
An alternative to /Tp is to change the source file from [tt]prog.cpp[/tt] to [tt]prog.c[/tt]


--
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.

 

[ushtabalakh]

#include "stdio.h"

#include "stdlib.h"





int *ChangeToDynamical(int a[],int size){

int *p;

if((p=malloc(size *sizeof(int)))==NULL)

	printf("Error\n");
int i;

for(i=0;i<size;size++){
	*p=a[i];
	p++;
}

return p;

}





int main(int argc, char *argv[])

{
	printf("starts here");
	int ii;

	int a[] = {1,2,3,4,5};
	char *c = ChangeToDynamical(a,5);


	for(ii=0;ii<5;ii++)
		printf("%d\n",c++);

}

Hey

This gives a permission error when I run it under linux

 

[ushtabalakh]

size++ should be changed to i++

I think there was a permission problem with execution that I solved but now when I run
gcc -c malloc.c
I get a malloc.o file
and when I type ./malloc.o
I get
bash: ./malloc.o: cannot execute binary file

How do I execute this file to see the result?

 

[xwb]

That will not generate an executable. -c only compiles: it does not link with libraries. You will need that for independent compilation when you have more than one source program. To build an executable

gcc -o memalloc malloc.c

The program is called whatever you specify after the -o. In this case memalloc. To execute

./memalloc

If you had just compiled as

gcc malloc.c

It would have generated a.out. You can also build with -c and then link later. Look up man pages on ar and ld on how to do this.

 

[Salem]

> char *c = ChangeToDynamical(a,5);
But your function returns int*, so what's with the cast to char* ?


--
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.

 

[mingis]

And you probably might want to printf("%d\n", *c++);

 

[cpjust]

Also, system headers are usually #included with <>, and custom headers use "".
Ex.

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