[PATCH] D25042: [libc++] Clarify _LIBCPP_NEW_DELETE_VIS for Windows

[Shoaib Meenai via cfe-commits]

smeenai updated this revision to Diff 72891.
smeenai added a comment.

Clarifying code comment


https://reviews.llvm.org/D25042

Files:
  include/new

Index: include/new
===================================================================
--- include/new
+++ include/new
@@ -125,8 +125,18 @@
 
 }  // std
 
-#if defined(_WIN32) && !defined(cxx_EXPORTS)
-# define _LIBCPP_NEW_DELETE_VIS _LIBCPP_FUNC_VIS_ONLY
+/*
+ * NOTE: When using the Microsoft CRT, the operator new and delete
+ * family of functions are defined statically in msvcrt.lib. Marking
+ * them as dllimport in this header is therefore undesirable: if we were
+ * to mark them dllimport and then link against libc++, source files
+ * which included <new> would end up linking against libc++'s new and
+ * delete, while source files which did not include <new> would end up
+ * still linking against msvcrt's new and delete, which would be a
+ * confusing and potentially error-prone inconsistency.
+ */
+#if defined(_LIBCPP_MSVCRT) && !defined(_LIBCPP_BUILDING_LIBRARY)
+# define _LIBCPP_NEW_DELETE_VIS
 #else
 # define _LIBCPP_NEW_DELETE_VIS _LIBCPP_FUNC_VIS
 #endif


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