PengZheng commented on code in PR #620:
URL: https://github.com/apache/celix/pull/620#discussion_r1304161309
##########
cmake/Modules/FindRapidJSON.cmake:
##########
@@ -28,8 +28,8 @@ find_package_handle_standard_args(RapidJSON DEFAULT_MSG
mark_as_advanced(RapidJSON_INCLUDE_DIR)
-if(RapidJSON_FOUND AND NOT TARGET RapidJSON::RapidJSON)
- add_library(RapidJSON::RapidJSON INTERFACE IMPORTED)
- set_target_properties(RapidJSON::RapidJSON PROPERTIES
INTERFACE_INCLUDE_DIRECTORIES
+if(RapidJSON_FOUND AND NOT TARGET rapidjson)
+ add_library(rapidjson INTERFACE IMPORTED)
+ set_target_properties(rapidjson PROPERTIES INTERFACE_INCLUDE_DIRECTORIES
"${RapidJSON_INCLUDE_DIRS}")
Review Comment:
> The reason is that downstream Apache Celix containers need to link against
rapidjson to ensure a functional C++ Remote Services. This requirement also
applies to ZerMQ and czmq, but then for PubSub ZMQ usage.
Fortunately, all these targets (zmq/czmq/libzip/rapidjson) need not to be
specified explicitly by our downstream users, since they are all linked
privately by their users, for exmaple `RsaConfiguredDiscovery`. For a container
containing `RsaConfiguredDiscovery`, e.g. `RemoteCalculatorConsumer`, there is
no need to refer to rapidjson/RapidJSON::RapidJSON directly. All needed
information is encoded in `DT_NEEDED` tag, the dynamic loader will find them
automatically provided the needed library is in the canonical search path.
I have removed many such unnecessary extra linkages in tests in the past two
years. They were needed because we have no BUILD_RPATH in the past. When they
are installed, even without BUILD_RPATH, our user will encounter no issue,
since Conan setup LD_LIBRARY_PATH to containing all dependencies (direct and
indirect).
> I believe this issue could be addressed with an additional alias:
add_library(RapidJSON::RapidJSON ALIAS rapidjson)
Our user may have encounter the same issue we had before, and resort to
explicit linking as we did before.
So I will add these alias in find modules to avoid breaking these usage.
There is indeed a interesting corner case: Conan does not describe CMake
private linkage well enough, we have the following workaround in Celix:
```
# the following is workaround
https://github.com/conan-io/conan/issues/7192
if self.settings.os == "Linux":
cmake.definitions["CMAKE_EXE_LINKER_FLAGS"] =
"-Wl,--unresolved-symbols=ignore-in-shared-libs"
elif self.settings.os == "Macos":
cmake.definitions["CMAKE_EXE_LINKER_FLAGS"] = "-Wl,-undefined
-Wl,dynamic_lookup"
```
Note that the above is to avoid build time linker error, there is nothing
wrong at run time (all information is encoded in DT_NEEDED correctly).
For more on this, see https://github.com/conan-io/conan/issues/13302
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