Thread: Problem with memory allocation

I am trying to allocate a dynamic array of number elements in which each element is of a structure type. The structure is

Code:

struct person
{
    char name[20]; 
    int age;
};
typedef struct person Person;

Here is what I have so far:
my main function:

Code:

int main( void )
{
    int number = 3;
    Person *p = allocate( number );
  
  system("PAUSE");	
  return 0;
}

Here is my allocate function so far:

Code:

struct person* allocate( int number )
{
    Person *people[number] = ( Person* ) malloc( sizeof( Person ) * number );
}

When I try to compile this, it tells me that variable-sized object cannot be initialized. I have tried everything I could think of. I am still new to C, so it might be obvious. What am I doing wrong?

Originally Posted by soulwarrior89

Code:

struct person* allocate( int number )
{
    Person *people[number] = ( Person* ) malloc( sizeof( Person ) * number );
}

When I try to compile this, it tells me that variable-sized object cannot be initialized. I have tried everything I could think of. I am still new to C, so it might be obvious. What am I doing wrong?

Part in red is so wrong. (You are making a pointer, not an array of pointers.)

What is sizeof(Person)? It is probably not what you think it is. The problem from the error is with 'Person *people[]'. As mentioned your, your allocate() is not returning anything...where is your return statement?

What is sizeof(Person)? It is probably not what you think it is.

What do you mean by that? sizeof(Person) is probably exactly what he thinks it is.

Originally Posted by Elysia

Why not? It seems to me that is exactly what the OP wants since Person is typedef for struct person. Ie, the function allocates n of struct person.

True, I somewhat overlooked

Code:

   char name[20]

My goof was that in showing the size of the struct here would only indicate the size of the pointer to name and not indicate that this actually contains 20 chars.

Thanks for the help! I didn't realize I was doing so many things wrong.

Originally Posted by laserlight

I think you missed:

Code:

typedef struct person Person;

But yeah, it is a little strange to use struct person when one made the typedef to use Person.

Yeah. Damn friggin C!

Originally Posted by Elysia

Remove the cast before malloc...

No. Read my comment as to why I need it. The compiler tells me I need it. Go play one-upmanship-standards-but-never-really-programming-for-a-living with Salem. Sorry, I'm getting a bit annoyed now.