smeenai created this revision. smeenai added reviewers: compnerd, EricWF, mclow.lists. smeenai added a subscriber: cfe-commits.
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. 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, 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
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, 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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