add _ENFORCE_ONLY_CORE_HEADERS (#2068)

Co-authored-by: Michael Schellenberger Costa <[email protected]>
Co-authored-by: Adam Bucior <[email protected]>
Co-authored-by: Stephan T. Lavavej <[email protected]>

Author: 4 people

stl/inc/yvals.h

@@ -9,6 +9,11 @@
 #include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
+#ifdef _ENFORCE_ONLY_CORE_HEADERS
+_EMIT_STL_ERROR(
+    STL1005, "Tried to include a non-core C++ Standard Library header file with _ENFORCE_ONLY_CORE_HEADERS defined.");
+#endif // _ENFORCE_ONLY_CORE_HEADERS
+
 #include <crtdbg.h>
 #include <crtdefs.h>
 

stl/inc/yvals_core.h

@@ -1232,6 +1232,8 @@ _EMIT_STL_ERROR(STL1004, "C++98 unexpected() is incompatible with C++23 unexpect
 
 // next warning number: STL4040
 
+// next error number: STL1006
+
 // P0619R4 Removing C++17-Deprecated Features
 #ifndef _HAS_FEATURES_REMOVED_IN_CXX20
 #define _HAS_FEATURES_REMOVED_IN_CXX20 (!_HAS_CXX20)

tests/std/tests/GH_001411_core_headers/test.cpp

@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 #define _CORE_HEADERS_ONLY
+#define _ENFORCE_ONLY_CORE_HEADERS // Also test GH-311 "Make it easy to limit the STL to core features"
 
 #include <__msvc_all_public_headers.hpp>