smeenai created this revision. When the libc++ extern template macros were added, the intent was for it to be possible for consumers of the headers to disable extern templates (via `-D_LIBCPP_EXTERN_TEMPLATE(...)=`). Unfortunately, support for specifying function-like macros varies on the command line varies across compilers (e.g. MSVC doesn't support it at all), and cmake doesn't allow it for the same reason. Add a non-function macro for this purpose.
The intended use is for libraries which want to use the libc++ headers without taking a dependency on the libc++ library itself. I can name the macro something which reflects its intent rather than its behavior (e.g. `_LIBCPP_HEADER_ONLY`) if desired. https://reviews.llvm.org/D31725 Files: include/__config Index: include/__config =================================================================== --- include/__config +++ include/__config @@ -837,6 +837,11 @@ # endif #endif +#ifdef _LIBCPP_DISABLE_EXTERN_TEMPLATE +#define _LIBCPP_EXTERN_TEMPLATE(...) +#define _LIBCPP_EXTERN_TEMPLATE2(...) +#endif + #ifndef _LIBCPP_EXTERN_TEMPLATE #define _LIBCPP_EXTERN_TEMPLATE(...) extern template __VA_ARGS__; #endif
Index: include/__config =================================================================== --- include/__config +++ include/__config @@ -837,6 +837,11 @@ # endif #endif +#ifdef _LIBCPP_DISABLE_EXTERN_TEMPLATE +#define _LIBCPP_EXTERN_TEMPLATE(...) +#define _LIBCPP_EXTERN_TEMPLATE2(...) +#endif + #ifndef _LIBCPP_EXTERN_TEMPLATE #define _LIBCPP_EXTERN_TEMPLATE(...) extern template __VA_ARGS__; #endif
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