function-definition: attribute-specifier-seq decl-specifier-seq declarator virt-specifier-seq function-body
function-body: ctor-initializer compound-statement function-try-block = default ; = delete ;Any informal reference to the body of a function should be interpreted as a reference to the non-terminal function-body.
static const char __func__[] = "function-name";
had been provided, where function-name is an implementation-defined string.struct S { S() : s(__func__) { } // OK const char* s; }; void f(const char* s = __func__); // error: __func__ is undeclared