3 minutes ago, Green_Baron said:

But this is not a string conversion warning but a qualifier warning, right ?

Right.  In C++ a string literal is of type "char const*" and assigning a pointer to const to a pointer to non-const without casting away the constness is not alllowed in C++.  Before C++11 there was an exception to the rule for string literals to provide backwards compatibility with C90 (which did not have const at all) but C++11 only required compatibility with C99, which does have const, so the exception to the rule was removed.