error: invalid conversion from 'char**' to 'const char**' [duplicate]

Question

I've got a function that requires const some_type** as an argument (some_type is a struct, and the function needs a pointer to an array of this type). I declared a local variable of type some_type*, and initialized it. Then I call the function as f(&some_array), and the compiler (gcc) says:

error: invalid conversion from ‘some_type**’ to ‘const some_type**’

What's the problem here? Why can't I convert a variable to const?

Answer 1

See: Why can't I pass a char ** to a function which expects a const char **? from the comp.lang.c FAQ.

Answer 2

You have a few options to get around what jamesdlin outlined in his answer.

You could use an intermediate variable.

some_type const* const_some_array = some_array;
f(&const_some_array);

You could change the parameters of f.

void f(some_type const* const* some_array);