initialize a multidimensional C array of variable size to zero

问题

I want to initialize a two-dimensional array of variable size to zero. I know it can be done for a fixed-sized array:

int myarray[10][10] = {0};

but it is not working if I do this:

int i = 10;
int j = 10;
int myarray[i][j] = {0};

Is there a one-line way of doing this or do I have to loop over each member of the array?

Thanks

回答1:

You cannot initialize it with an initializer, but you can memset() the array to 0.

#include <string.h>

int main(void) {
  int a = 13, b = 42;
  int m[a][b];
  memset(m, 0, sizeof m);
  return 0;
}

Note: this is C99. In C89 the declaration of m ( int m[a][b]; ) is an error.

回答2:

Online C99 Standard (n1256 draft), Section 6.7.8, para 3:

The type of the entity to be initialized shall be an array of unknown size or an object type that is not a variable length array type.

Emphasis mine.

As everyone else has said, your best bet is to use memset().

回答3:

If you get a pointer to your data structure, you could try memset.

回答4:

You can't create a static array using non-constant variables. Try using dynamic allocation:

int i = 10;
int j = 10;
size_t nbytes = i*j*sizeof(int);
int* myarray = (int*) malloc(nbytes);
memset(myarray,0,nbytes);

回答5:

Variable size two dimensional arrays are not supported in C. One dimension (i can't remember if it is first or second) has to be fixed. I recommend looping over it once it is defined.

来源：https://stackoverflow.com/questions/3718716/initialize-a-multidimensional-c-array-of-variable-size-to-zero

标签

arrays

initialization