Problem in malloc

was studying about dynamic memory today but when i did this code it didnt compile with
msv6 but compiled with dev C++
anyways here the code

Code:

#include <stdio.h>
#include <stdlib.h>
int main()
{
int *integers;
int required=3;
int i;
integers=malloc(required*sizeof(int));
if(integers==NULL)
{
puts("Malloc failed");
exit(1);
}
for(i=0;i<required;i++)
{
printf("Please enter number #%d: ",i+1);
getchar();
scanf("%d",&integers[i]);
}
for(i=0;i<required;i++)
{
	printf("Number #%d was %d\n",i+1,integers[i]);
	getchar();
}
return 0;
}

What errors did you get?

For those of us that don't have either Dev C++, or msV6, or who might not even be on Windows, pray tell, what's the error you get?

D:\c_LESSONS_TUTRIALS_MADE_BY_ME\malloc\main.cpp(8 ) : error C2440: '=' : cannot convert from 'void *' to 'int *'

yaah srry to forgot to post error

you are compiling your C code as C++ (C supports implicit casts from void pointers, C++ doesn't).

I think you need an array of pointesr to do the job:

Code:

int *integers[3];

You have only allocated memory to integers, which is really integers[0], therefore integers[1] & integers[2] have not had memory allocated.

================

EDIT: If

Code:

int *integers;

is declared, but

Code:

integers[i]

is used in the program, shouldn't the compiler give a warning?

===================

So you have to use malloc to allocate memory to all 3 pointers, right before the user inputs each number:

Code:

for ( i = 0; i < required; i++ )
{
    printf("Please enter number #%d: ",i+1);
   intergers[i] = malloc( sizeof(int) );
   scanf("%d",&integers[i]);
}

and then you have to free the memory malloc has allocated to each pointer:

Code:

for(i=0;i<required;i++)
{
	printf("Number #%d was %d\n",i+1,integers[i]);
	getchar();
         free(integers[i]); 
}

Originally Posted by cyberfish

you are compiling your C code as C++ (C supports implicit casts from void pointers, C++ doesn't).

And to fix that, all you actually need to do is rename the file from something.cpp to something.c and MS VC will automatically use the C flavour of it's compiler, rather than the C++ flavour.

--
Mats

yah thanks it compiles cool now thanks mats i dunno why in msv6 you cant compile as .c alawys .cpp

Originally Posted by lolguy

yah thanks it compiles cool now thanks mats i dunno why in msv6 you cant compile as .c alawys .cpp

You CAN compile C as well as C++ in MSVC6, you just have to make sure that when you create the file, you name it as .c rather than .cpp which the IDE insists on if you don't give it a different extension.

--
Mats

yah i have to rename but when i start new project and new file there option only C++ source file there is no C source file

Originally Posted by lolguy

yah i have to rename but when i start new project and new file there option only C++ source file there is no C source file

Yeah. I use the "Add new item..." in the Project view instead of the New File ... dialog - but I'm also using the next release of Visual Studio (.Net) rather than 6 - I think I still have 6 somewhere on my machine, but I'm not sure. ... Actually, I have VS 5.0 - and I think VS 6 is similar - when you select "New file ...", just click on the C++ file type, and then make the extension .c, and you should be fine.

--
Mats

oh cool thanks alot mate

Originally Posted by happyclown

================

EDIT: If

Code:

int *integers;

is declared, but

Code:

integers[i]

is used in the program, shouldn't the compiler give a warning?

Well, but, why? Given that the OP's usage was perfectly correct, and in fact declaring a pointer and then mallocing memory is pretty much the only way to do dynamic memory allocation in C, then a whole heck of a lot of code would fall under this restriction.

Well, is it to okay to declare a pointer of type int( int *integers), and then use an array of type int[integers[i]), which hasn't been declared? But the compiler didn't give a warning about the undeclared array?

EDIT: so is

Code:

int *integers;

the same as

Code:

int integers[i]?

where i > 0?

I am a newbie, so maybe I am missing something(s)?