Question

If I have a function:

void myfunction(char** s);

Then I can pass a char* like this:

char* s = malloc(100);
myfunction(&s);

But my compiler won’t allow me to do this:

char s[100] = {0};
myfunction(&s);

I thought that a pointer to the buffer should be allowed by the compiler.

Answer 1

Your function expects a pointer to a pointer (char **). You are trying to pass a pointer to an array instead (char (*)[100]). Why do you expect this to “be allowed by the compiler”? Arrays are not pointers. Arrays and pointers are objects of completely different nature. A pointer to a pointer is not in any way compatible with a pointer to an array. You can’t use them interchangeably.

If you want you use your array-based buffer with a function that expects char **, you have to explicitly create a pointer to that buffer first

char s[100] = {0};
char *ps = s;

and then pass a pointer to that pointer, as you did before

myfunction(&ps);