Pointer to string changes its value unexpectedly

Question

I have noted that, when writing a string in an array allocated with malloc(), its value changes. To be clear, here is the code that replicates this \"error\":

Answer 1

Your problem

You are allocating memory for your pointer with malloc() but then you assign your pointer variable to something else ("something", which has its own address), instead of filling the newly-allocated pointer.

Solution

You should use the strdup() function that allocates memory and copies a string at the allocated memory:

a_p = strdup("something");

Or the strcpy() function, that takes a malloc()'d pointer and a string to copy in the pointed memory:

a_p = malloc(N * sizeof(char));
strcpy(a_p, "something");