Implemented C++23 deleted nullptr_t constructor/assignment for AZStd string classes (#4158)

* Added string and string_view class constructor overloads which is deleted that prevents initializing them from a nullptr or an integer type

Signed-off-by: lumberyard-employee-dm <56135373+lumberyard-employee-dm@users.noreply.github.com>

* Fixed locations where string and string_view were initialized with
nullptr

Signed-off-by: lumberyard-employee-dm <56135373+lumberyard-employee-dm@users.noreply.github.com>

* Fix IArchive::IsInstalledToHDD signature

Updated calls to ConvertAbsolutePathToAliasedPath to use an
list initialization instead of nullptr

Signed-off-by: lumberyard-employee-dm <56135373+lumberyard-employee-dm@users.noreply.github.com>

Code/Framework/AzCore/AzCore/std/string/fixed_string.h

@@ -96,6 +96,10 @@ namespace AZStd
             && !is_convertible_v<const T&, const Element*>>>
         constexpr basic_fixed_string(const T& convertibleToView, size_type rhsOffset, size_type count);
 
+
+        // #12
+        constexpr basic_fixed_string(AZStd::nullptr_t) = delete;
+
         constexpr operator AZStd::basic_string_view<Element, Traits>() const;
 
         constexpr auto begin() -> iterator;
@@ -120,6 +124,7 @@ namespace AZStd
         constexpr auto operator=(const T& convertible_to_view)
             -> AZStd::enable_if_t<is_convertible_v<const T&, basic_string_view<Element, Traits>>
             && !is_convertible_v<const T&, const Element*>, basic_fixed_string&>;
+        constexpr auto operator=(AZStd::nullptr_t) -> basic_fixed_string& = delete;
 
         constexpr auto operator+=(const basic_fixed_string& rhs) -> basic_fixed_string&;
         constexpr auto operator+=(const_pointer ptr) -> basic_fixed_string&;

Code/Framework/AzCore/AzCore/std/string/string.h

@@ -168,6 +168,9 @@ namespace AZStd
         {
         }
 
+        // C++23 overload to prevent initializing a string_view via a nullptr or integer type
+        constexpr basic_string(AZStd::nullptr_t) = delete;
+
         inline ~basic_string()
         {
             // destroy the string
@@ -197,6 +200,7 @@ namespace AZStd
         inline this_type& operator=(AZStd::basic_string_view<Element, Traits> view) { return assign(view); }
         inline this_type& operator=(const_pointer ptr)          { return assign(ptr); }
         inline this_type& operator=(Element ch)             { return assign(1, ch); }
+        inline this_type& operator=(AZStd::nullptr_t) = delete;
         inline this_type& operator+=(const this_type& rhs)      { return append(rhs); }
         inline this_type& operator+=(const_pointer ptr)     { return append(ptr); }
         inline this_type& operator+=(Element ch)                { return append(1, ch); }

Code/Framework/AzCore/AzCore/std/string/string_view.h

@@ -502,6 +502,9 @@ namespace AZStd
             swap(other);
         }
 
+        // C++23 overload to prevent initializing a string_view via a nullptr or integer type
+        constexpr basic_string_view(AZStd::nullptr_t) = delete;
+
         constexpr const_reference operator[](size_type index) const { return data()[index]; }
         /// Returns value, not reference. If index is out of bounds, 0 is returned (can't be reference).
         constexpr value_type at(size_type index) const