[PATCH] D25042: [libc++] Clarify _LIBCPP_NEW_DELETE_VIS for Windows
Shoaib Meenai via cfe-commits
cfe-commits at lists.llvm.org
Wed Sep 28 15:12:12 PDT 2016
smeenai updated this revision to Diff 72911.
smeenai added a comment.
Moving documentation to documentation file, per @EricWF's comment
@@ -125,8 +125,8 @@
} // std
-#if defined(_WIN32) && !defined(cxx_EXPORTS)
-# define _LIBCPP_NEW_DELETE_VIS _LIBCPP_FUNC_VIS_ONLY
+#if defined(_LIBCPP_MSVCRT) && !defined(_LIBCPP_BUILDING_LIBRARY)
+# define _LIBCPP_NEW_DELETE_VIS
# define _LIBCPP_NEW_DELETE_VIS _LIBCPP_FUNC_VIS
@@ -108,6 +108,19 @@
versioning namespace. This allows throwing and catching some exception types
between libc++ and libstdc++.
+ Mark a symbol as being exported by the libc++ library. This macro must be
+ applied to all `operator new` and `operator delete` overloads.
+ **Windows Behavior**: When using the Microsoft CRT, all the `operator new` and
+ `operator delete` overloads are defined statically in `msvcrt.lib`. Marking
+ them as `dllimport` in the libc++ `<new>` header is therefore undesirable: if
+ we were to mark them as `dllimport` and then link against libc++, source files
+ which included `<new>` would end up linking against libc++'s `operator new`
+ and `operator delete`, while source files which did not include `<new>` would
+ end up linking against msvcrt's `operator new` and `operator delete`, which
+ would be a confusing and potentially error-prone inconsistency.
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