Partial GCC compatibility improvements (#1234)

Author: alvinhochun

cppwinrt/pch.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <utility>
 #include "cmd_reader.h"
 #include <winmd_reader.h>
 #include "task_group.h"

cppwinrt/text_writer.h

@@ -6,6 +6,7 @@
 #include <sstream>
 #include <string>
 #include <string_view>
+#include <vector>
 
 namespace cppwinrt
 {

strings/base_chrono.h

@@ -47,7 +47,7 @@ WINRT_EXPORT namespace winrt
 
         static time_point from_time_t(time_t time) noexcept
         {
-            return from_sys(std::chrono::system_clock::from_time_t(time));
+            return std::chrono::time_point_cast<duration>(from_sys(std::chrono::system_clock::from_time_t(time)));
         }
 
         static file_time to_file_time(time_point const& time) noexcept

strings/base_includes.h

@@ -6,6 +6,7 @@
 #include <charconv>
 #include <chrono>
 #include <cstddef>
+#include <cstring>
 #include <iterator>
 #include <map>
 #include <memory>
@@ -20,6 +21,10 @@
 #include <utility>
 #include <vector>
 
+#if __has_include(<version>)
+#include <version>
+#endif
+
 #if __has_include(<windowsnumerics.impl.h>)
 #define WINRT_IMPL_NUMERICS
 #include <directxmath.h>
@@ -50,7 +55,7 @@ namespace winrt::impl
     using suspend_never = std::suspend_never;
 }
 
-#else
+#elif __has_include(<experimental/coroutine>)
 
 #include <experimental/coroutine>
 
@@ -63,4 +68,6 @@ namespace winrt::impl
     using suspend_never = std::experimental::suspend_never;
 }
 
+#else
+#error C++/WinRT requires coroutine support, which is currently missing. Try enabling C++20 in your compiler.
 #endif

strings/base_string_operators.h

@@ -55,9 +55,9 @@ WINRT_EXPORT namespace winrt
         return left < std::wstring_view(right);
     }
 
-    bool operator<(hstring const& left, nullptr_t) = delete;
+    bool operator<(hstring const& left, std::nullptr_t) = delete;
 
-    bool operator<(nullptr_t, hstring const& right) = delete;
+    bool operator<(std::nullptr_t, hstring const& right) = delete;
     inline bool operator!=(hstring const& left, hstring const& right) noexcept { return !(left == right); }
     inline bool operator>(hstring const& left, hstring const& right) noexcept { return right < left; }
     inline bool operator<=(hstring const& left, hstring const& right) noexcept { return !(right < left); }