Compile error assigning `__func__` to `_Nt_array_ptr<const char>` in unchecked scope

[kyleheadley]

The predefined identifier __func__ represents the name of the enclosing function as a const char []. This is used in macros in 3C's icecast benchmark. It can be assigned to an _Nt_array_ptr<const char>, but only in a checked scope. 3C doesn't insert that checked scope without -addcr and block safety, but still rewrites to the nt array pointer.

We need a better way to handle these situations.

[john-h-kastner]

A concrete failing test case:

#include<string.h>
void test(void) {
  char *d = __func__;
  strlen(d);
}

converts to

#include<string.h>
void test(void) {
  _Nt_array_ptr<char> d = __func__;
  strlen(d);
}

but this fails to compile with

error: initializing '_Nt_array_ptr<char>' with an expression of incompatible type 'const char [5]'
  _Nt_array_ptr<char> d = __func__;

[mattmccutchen-cci]

It looks like a cast would come to our rescue again, just as in #725:

void test(void) {
  // Error
  _Nt_array_ptr<char> p = __func__;
  // No error
  _Nt_array_ptr<char> p2 = (_Nt_array_ptr<char>) __func__;
}

We can go ahead and do that in 3C. Ideally, we'd also file a bug against the compiler.