[libc++] Clarify _LIBCPP_NEW_DELETE_VIS for Windows Replace a stale reference to cxx_EXPORTS with _LIBCPP_BUILDING_LIBRARY, and clarify why the operator new and delete family of functions are marked dllexport when building but *not* dllimport when including the header externally. The new code is identical to the intent of the old code (and would be functionally equivalent were cxx_EXPORTS still defined when building libc++). The overall behavior is not ideal, since Microsoft's operator new and delete functions will get called instead of libc++'s, but I think consistently calling msvcrt's functions is better than either calling msvcrt's or libc++'s functions depending on header inclusion. Differential Revision: https://reviews.llvm.org/D25042 git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@282644 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/DesignDocs/VisibilityMacros.rst b/docs/DesignDocs/VisibilityMacros.rst index f7d1400..f45d67b 100644 --- a/docs/DesignDocs/VisibilityMacros.rst +++ b/docs/DesignDocs/VisibilityMacros.rst
@@ -108,6 +108,19 @@ versioning namespace. This allows throwing and catching some exception types between libc++ and libstdc++. +**_LIBCPP_NEW_DELETE_VIS** + 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. + Links =====
diff --git a/include/new b/include/new index 936f9ee..16b3011 100644 --- a/include/new +++ b/include/new
@@ -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 #else # define _LIBCPP_NEW_DELETE_VIS _LIBCPP_FUNC_VIS #endif
