CMake: Add absl::abseil_dll ALIAS target for abseil_dll #1466
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This additional if is necessary as of abseil 20230125.3 when abseil is consumed via add_subdirectory, the abseil_dll target is named abseil_dll, while if abseil is consumed via find_package, the target is called `absl::abseil_dll` . Once abseil/abseil-cpp#1466 is merged and released in the minimum version of abseil required by protobuf, it is possible to always link `absl::abseil_dll` and `absl::abseil_test_dll` and remove the if. You may wonder how linking worked at all before when `protobuf_ABSL_PROVIDER STREQUAL "package"`, as `abseil_dll` was not an imported target defined by `find_package(absl)`. The reason behind this is that if a name that is not an imported target is passed to `target_link_libraries`, it is just regarded as a C++ library name. So, in the end the `abseil_dll` library was correctly linked, simply all the transitive usage requirements defined by the `absl::abseil_dll` target were not propagated, that could lead to compilation errors if abseil was compiled with the `ABSL_PROPAGATE_CXX_STD` CMake option enabled. Closes #12978 COPYBARA_INTEGRATE_REVIEW=#12978 from traversaro:patch-1 39dd074 PiperOrigin-RevId: 537990391
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This additional if is necessary as of abseil 20230125.3 when abseil is consumed via add_subdirectory, the abseil_dll target is named abseil_dll, while if abseil is consumed via find_package, the target is called `absl::abseil_dll` . Once abseil/abseil-cpp#1466 is merged and released in the minimum version of abseil required by protobuf, it is possible to always link `absl::abseil_dll` and `absl::abseil_test_dll` and remove the if. You may wonder how linking worked at all before when `protobuf_ABSL_PROVIDER STREQUAL "package"`, as `abseil_dll` was not an imported target defined by `find_package(absl)`. The reason behind this is that if a name that is not an imported target is passed to `target_link_libraries`, it is just regarded as a C++ library name. So, in the end the `abseil_dll` library was correctly linked, simply all the transitive usage requirements defined by the `absl::abseil_dll` target were not propagated, that could lead to compilation errors if abseil was compiled with the `ABSL_PROPAGATE_CXX_STD` CMake option enabled. Closes #12978 COPYBARA_INTEGRATE_REVIEW=#12978 from traversaro:patch-1 39dd074 FUTURE_COPYBARA_INTEGRATE_REVIEW=#12978 from traversaro:patch-1 39dd074 PiperOrigin-RevId: 537953985
h-vetinari
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…ocolbuffers#12978) This additional if is necessary as of abseil 20230125.3 when abseil is consumed via add_subdirectory, the abseil_dll target is named abseil_dll, while if abseil is consumed via find_package, the target is called `absl::abseil_dll` . Once abseil/abseil-cpp#1466 is merged and released in the minimum version of abseil required by protobuf, it is possible to always link `absl::abseil_dll` and `absl::abseil_test_dll` and remove the if. You may wonder how linking worked at all before when `protobuf_ABSL_PROVIDER STREQUAL "package"`, as `abseil_dll` was not an imported target defined by `find_package(absl)`. The reason behind this is that if a name that is not an imported target is passed to `target_link_libraries`, it is just regarded as a C++ library name. So, in the end the `abseil_dll` library was correctly linked, simply all the transitive usage requirements defined by the `absl::abseil_dll` target were not propagated, that could lead to compilation errors if abseil was compiled with the `ABSL_PROPAGATE_CXX_STD` CMake option enabled. Closes protocolbuffers#12978 COPYBARA_INTEGRATE_REVIEW=protocolbuffers#12978 from traversaro:patch-1 39dd074 PiperOrigin-RevId: 537990391
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This PR adds a
absl::abseil_dllALIAS target for theabseil_dll.ALIAS targets are used in CMake to ensure that consumers that consume the library via CMake's FetchContent or in general via
add_subdirectorycan use the exact same targets found by consuming abseil viafind_package(absl REQUIRED).For all other absl targets, the
ALIAStarget is added by theabsl_cc_librarycmake function ( https://github.com/abseil/abseil-cpp/blob/20230125.3/CMake/AbseilHelpers.cmake#L53 ). However, theabseil_dlltarget is not created via theabsl_cc_librarybut instead with a direct call to theadd_libraryCMake function, so it is necessary to also add anALIAStarget explicitly.After this PR, it is possible to just link
absl::abseil_dll, both when abseil is obtained via FetchContent of via find_package. Before this PR, if abseil was obtained viaFetchContentit was necessarry to linkabseil_dll, while iffind_package(absl REQUIRED)was used, it was necessary to linkabsl::abseil_dll.