Why does malloc initialize the values to 0 in gcc?

Question

Maybe it is different from platform to platform, but

when I compile using gcc and run the code below, I get 0 every time in my ubuntu 11.10.

#include         


        

Answer 1

I modified your example to contain 2 identical allocations. Now it is easy to see malloc doesn't zero initialize memory.

#include 
#include 

int main(void)
{
    {
      double *a = malloc(sizeof(double)*100);
      *a = 100;
      printf("%f\n", *a);
      free(a);
    }
    {
      double *a = malloc(sizeof(double)*100);
      printf("%f\n", *a);
      free(a);
    }

    return 0;
}

Output with gcc 4.3.4

100.000000
100.000000