Reform deprecation messages and add more comments

Author: frederick-vs-ja

libcxx/include/ccomplex

@@ -23,17 +23,16 @@
 #  pragma GCC system_header
 #endif
 
-#if _LIBCPP_STD_VER >= 17
-
-using __standard_header_ccomplex
-#  if _LIBCPP_STD_VER >= 20
-    _LIBCPP_DEPRECATED_("removed in C++20. Include <complex> instead.")
-#  else
-    _LIBCPP_DEPRECATED_("Include <complex> instead.")
-#  endif
-    = void;
+#if _LIBCPP_STD_VER >= 20
+
+using __standard_header_ccomplex _LIBCPP_DEPRECATED_("removed in C++20. Include <complex> instead.") = void;
 using __use_standard_header_ccomplex = __standard_header_ccomplex;
 
+#else if _LIBCPP_STD_VER >= 17
+
+using __standard_header_ccomplex _LIBCPP_DEPRECATED_("Include <complex> instead.") = void;
+using __use_standard_header_ccomplex                                               = __standard_header_ccomplex;
+
 #endif
 
 #endif // _LIBCPP_CCOMPLEX

libcxx/include/cstdalign

@@ -40,16 +40,15 @@ Macros:
 #undef __alignof_is_defined
 #define __alignof_is_defined 1
 
-#if _LIBCPP_STD_VER >= 17
+#if _LIBCPP_STD_VER >= 20
 
-using __standard_header_cstdalign
-#  if _LIBCPP_STD_VER >= 20
-    _LIBCPP_DEPRECATED_("removed in C++20.")
-#  else
-    _LIBCPP_DEPRECATED
-#  endif
-    = void;
-using __use_standard_header_cstdalign = __standard_header_cstdalign;
+using __standard_header_cstdalign _LIBCPP_DEPRECATED_("removed in C++20.") = void;
+using __use_standard_header_cstdalign                                      = __standard_header_cstdalign;
+
+#else if _LIBCPP_STD_VER >= 17
+
+using __standard_header_cstdalign _LIBCPP_DEPRECATED = void;
+using __use_standard_header_cstdalign                = __standard_header_cstdalign;
 
 #endif
 

libcxx/include/cstdbool

@@ -28,16 +28,15 @@ Macros:
 #undef __bool_true_false_are_defined
 #define __bool_true_false_are_defined 1
 
-#if _LIBCPP_STD_VER >= 17
-
-using __standard_header_cstdbool
-#  if _LIBCPP_STD_VER >= 20
-    _LIBCPP_DEPRECATED_("removed in C++20.")
-#  else
-    _LIBCPP_DEPRECATED
-#  endif
-    = void;
-using __use_standard_header_cstdbool = __standard_header_cstdbool;
+#if _LIBCPP_STD_VER >= 20
+
+using __standard_header_cstdbool _LIBCPP_DEPRECATED_("removed in C++20.") = void;
+using __use_standard_header_cstdbool                                      = __standard_header_cstdbool;
+
+#else if _LIBCPP_STD_VER >= 17
+
+using __standard_header_cstdbool _LIBCPP_DEPRECATED = void;
+using __use_standard_header_cstdbool                = __standard_header_cstdbool;
 
 #endif
 

libcxx/include/ctgmath

@@ -25,15 +25,14 @@
 #  pragma GCC system_header
 #endif
 
-#if _LIBCPP_STD_VER >= 17
-
-using __standard_header_ctgmath
-#  if _LIBCPP_STD_VER >= 20
-    _LIBCPP_DEPRECATED_("removed in C++20. Include <cmath> and <complex> instead.")
-#  else
-    _LIBCPP_DEPRECATED_("Include <cmath> and <complex> instead.")
-#  endif
-    = void;
+#if _LIBCPP_STD_VER >= 20
+
+using __standard_header_ctgmath _LIBCPP_DEPRECATED_("removed in C++20. Include <cmath> and <complex> instead.") = void;
+using __use_standard_header_ctgmath = __standard_header_ctgmath;
+
+#else if _LIBCPP_STD_VER >= 17
+
+using __standard_header_ctgmath _LIBCPP_DEPRECATED_("Include <cmath> and <complex> instead.") = void;
 using __use_standard_header_ctgmath = __standard_header_ctgmath;
 
 #endif

libcxx/test/std/depr/depr.c.headers/stdalign_h.compile.pass.cpp

@@ -11,7 +11,7 @@
 // Even though <stdalign.h> is not provided by libc++,
 // we still test that using it with libc++ on the search path will work.
 
-// TODO: GCC doesn't provide a proper <stdalign.h>.
+// TODO: GCC doesn't provide a proper <stdalign.h> for C++ until 15.
 // UNSUPPORTED: gcc
 
 #include <stdalign.h>