CXX-2745 Add advanced CMake options to toggle root namespace redeclarations (#1324)

* Apply default ABI override to polyfills

Author: eramongodb

cmake/BsoncxxUtil.cmake

@@ -117,6 +117,10 @@ function(bsoncxx_add_library TARGET OUTPUT_NAME LINK_TYPE)
         DEFINE_SYMBOL BSONCXX_EXPORT
     )
 
+    if(BSONCXX_API_OVERRIDE_DEFAULT_ABI)
+        target_compile_definitions(${TARGET} PUBLIC BSONCXX_API_OVERRIDE_DEFAULT_ABI)
+    endif()
+
     if(ENABLE_ABI_TAG_IN_LIBRARY_FILENAMES)
         set_target_properties(${TARGET} PROPERTIES OUTPUT_NAME ${OUTPUT_NAME}${abi_tag})
     else()

cmake/MongocxxUtil.cmake

@@ -79,6 +79,10 @@ function(mongocxx_add_library TARGET OUTPUT_NAME LINK_TYPE)
         DEFINE_SYMBOL MONGOCXX_EXPORTS
     )
 
+    if(MONGOCXX_API_OVERRIDE_DEFAULT_ABI)
+        target_compile_definitions(${TARGET} PUBLIC MONGOCXX_API_OVERRIDE_DEFAULT_ABI)
+    endif()
+
     if(ENABLE_ABI_TAG_IN_LIBRARY_FILENAMES)
         set_target_properties(${TARGET} PROPERTIES OUTPUT_NAME ${OUTPUT_NAME}${abi_tag})
     else()

src/bsoncxx/CMakeLists.txt

@@ -23,6 +23,12 @@ message(STATUS "bsoncxx version: ${BSONCXX_VERSION}")
 option(BSONCXX_POLY_USE_IMPLS "Use bsoncxx implementations for stdx polyfills" OFF)
 option(BSONCXX_POLY_USE_STD "Use C++17 std library for stdx polyfills" OFF)
 
+option(BSONCXX_API_OVERRIDE_DEFAULT_ABI "The default ABI namespace to use for root namespace redeclarations" OFF)
+mark_as_advanced(BSONCXX_API_OVERRIDE_DEFAULT_ABI)
+if(BSONCXX_API_OVERRIDE_DEFAULT_ABI)
+    message(WARNING "BSONCXX_API_OVERRIDE_DEFAULT_ABI is an experimental feature")
+endif()
+
 set(BSONCXX_OUTPUT_BASENAME "bsoncxx" CACHE STRING "Output bsoncxx library base name")
 
 # Count how many polyfill options are true-ish

src/bsoncxx/include/bsoncxx/v_noabi/bsoncxx/stdx/optional.hpp

@@ -34,13 +34,26 @@ using v1::stdx::optional;
 namespace bsoncxx {
 namespace stdx {
 
+#if defined(BSONCXX_API_OVERRIDE_DEFAULT_ABI)
+
+using v1::stdx::in_place;
+using v1::stdx::in_place_t;
+using v1::stdx::make_optional;
+using v1::stdx::nullopt;
+using v1::stdx::nullopt_t;
+using v1::stdx::optional;
+
+#else
+
 using v_noabi::stdx::in_place;
 using v_noabi::stdx::in_place_t;
 using v_noabi::stdx::make_optional;
 using v_noabi::stdx::nullopt;
 using v_noabi::stdx::nullopt_t;
 using v_noabi::stdx::optional;
 
+#endif // defined(BSONCXX_API_OVERRIDE_DEFAULT_ABI)
+
 } // namespace stdx
 } // namespace bsoncxx
 

src/bsoncxx/include/bsoncxx/v_noabi/bsoncxx/stdx/string_view.hpp

@@ -30,9 +30,18 @@ using v1::stdx::string_view;
 namespace bsoncxx {
 namespace stdx {
 
+#if defined(BSONCXX_API_OVERRIDE_DEFAULT_ABI)
+
+using v1::stdx::basic_string_view;
+using v1::stdx::string_view;
+
+#else
+
 using v_noabi::stdx::basic_string_view;
 using v_noabi::stdx::string_view;
 
+#endif // defined(BSONCXX_API_OVERRIDE_DEFAULT_ABI)
+
 } // namespace stdx
 } // namespace bsoncxx
 

src/mongocxx/CMakeLists.txt

@@ -23,6 +23,12 @@ message(STATUS "mongocxx version: ${MONGOCXX_VERSION}")
 option(MONGOCXX_ENABLE_SSL "Enable SSL - if the underlying C driver offers it" ON)
 option(MONGOCXX_ENABLE_SLOW_TESTS "Run slow tests when invoking the the test target" OFF)
 
+option(MONGOCXX_API_OVERRIDE_DEFAULT_ABI "The default ABI namespace to use for root namespace redeclarations" OFF)
+mark_as_advanced(MONGOCXX_API_OVERRIDE_DEFAULT_ABI)
+if(MONGOCXX_API_OVERRIDE_DEFAULT_ABI)
+    message(WARNING "MONGOCXX_API_OVERRIDE_DEFAULT_ABI is an experimental feature")
+endif ()
+
 set(MONGOCXX_OUTPUT_BASENAME "mongocxx" CACHE STRING "Output mongocxx library base name")
 
 set(MONGOCXX_PKG_DEP "") # Required by mongocxx-config.cmake.in.