2D array - invalid initializer in C?

Question

Hey guys I'm trying to initialize a 2D char array but am having trouble.

int size = 300 * 400;
char * frame[3] = malloc(sizeof(char *)*size*3);

Gives m: error: invalid initializer. So I tried:

int size = 300 * 400;
char frame[3][size] = malloc(sizeof(char *)*size*3);

But then I get error: variable-sized object may not be initialized?

Any ideas how I can initialize an array of size 300*400 with 3 rows?

Thanks.

Not all C/C++ compilers support declaring an array using a variable size. — Ramesh Rajendran
– Ramesh Rajendran, Commented Apr 23, 2013 at 9:27
Are you trying to allocate an array of 3 character pointers to buffers of 120000 characters ? What is the point of the 300 * 400 - some kind of array in an array? — Mark Bertenshaw
– Mark Bertenshaw, Commented Apr 23, 2013 at 9:29

Kiril Kirov · Accepted Answer · 2013-04-23 09:27:40Z

2

You can try:

int size = 300 * 400;
const int rows_number = 3;
char* frame[ rows_number ]; // crate array with 3 elements, each of them `char*`
for( unsigned ii = 0; ii < rows_number; ++ii )
{
    // allocate `size` char`s for each "row"
    frame[ ii ] = malloc( sizeof(char) * size ); 
    // do not forget to free this memory later
}

answered Apr 23, 2013 at 9:27

Kiril Kirov

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1 Comment

Kiril Kirov Over a year ago

@H2CO3 - I know, but it's compile time and it's more readable (at least to me)

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