Dynamic array in C cause segmentation fault

问题

I have defined a dynamic array this way:

double   *n_data ;
int n_data_c = 0, n_cnt = 0;
n_data_c = count_lines_of_file("abnorm");
n_data = (double *)malloc(n_data_c * sizeof(double));

in a loop I calculate distance and do so:

n_cnt++;
n_data[n_cnt] = distance;

but it returns segmentation fault here : n_data[n_cnt] = distance;

I want to know if I'm doing something wrong.

回答1:

Check what malloc returned, if it returned 0, then it failed. More likely, I think, is your n_cnt is out of bounds. If it's negative, or greater than or equal to n_data_c, then you'll get a segfault.

回答2:

You are overrunning your array buffer..

Compare n_cnt with n_data_c and only access the array if n_cnt < n_data_c/

n_cnt++;
if (n_cnt < n_data_c)
{
n_data[n_cnt] = distance;
}

回答3:

n_data_c = count_lines_of_file("abnorm");

this is generating the segmentation fault. Check the value of n_data_c

回答4:

Just try printing the value of n_data_c before mallocing.

来源：https://stackoverflow.com/questions/21872616/dynamic-array-in-c-cause-segmentation-fault