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https://issues.apache.org/jira/browse/DISPATCH-2178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17368409#comment-17368409
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ASF GitHub Bot commented on DISPATCH-2178:
------------------------------------------
jiridanek commented on a change in pull request #1267:
URL: https://github.com/apache/qpid-dispatch/pull/1267#discussion_r655416842
##########
File path: tests/CMakeLists.txt
##########
@@ -40,8 +40,8 @@ set(unit_test_SOURCES
thread_test.c
)
-add_executable(unit_tests ${unit_test_SOURCES})
-target_link_libraries(unit_tests qpid-dispatch)
+add_executable(unit_tests ${unit_test_SOURCES} $<TARGET_OBJECTS:qpid-dispatch>)
+target_link_libraries(unit_tests qpid-dispatch-libraries)
Review comment:
The static library is empty, it is only a CMake target that carries
dependencies of qpid-dispatch. Like INTERFACE library, but that is not
supported in CMake 3.8.12.2. I have to propagate the PUBLIC/INTERFACE
dependencies of the object files in `$<TARGET_OBJECTS:qpid-dispatch>` somehow.
If I had CMake 3.12, I could do `target_link_libraries(unit_tests
qpid-dispatch)` and be done with it. For older CMake, I have to add the object
files into `add_executable`, but that does nothing about link dependencies. So
I'd have to have e.g. a variable.... I thought that a `-libraries` static
library containing no symbols of its own is cleaner. (The library will actually
have to contain something due to the macOS error I mentioned above.)
##########
File path: tests/CMakeLists.txt
##########
@@ -40,8 +40,8 @@ set(unit_test_SOURCES
thread_test.c
)
-add_executable(unit_tests ${unit_test_SOURCES})
-target_link_libraries(unit_tests qpid-dispatch)
+add_executable(unit_tests ${unit_test_SOURCES} $<TARGET_OBJECTS:qpid-dispatch>)
+target_link_libraries(unit_tests qpid-dispatch-libraries)
Review comment:
The static library is empty, it is only a CMake target that carries
dependencies of qpid-dispatch. Like INTERFACE library, but that is not
supported in CMake 2.8.12.2. I have to propagate the PUBLIC/INTERFACE
dependencies of the object files in `$<TARGET_OBJECTS:qpid-dispatch>` somehow.
If I had CMake 3.12, I could do `target_link_libraries(unit_tests
qpid-dispatch)` and be done with it. For older CMake, I have to add the object
files into `add_executable`, but that does nothing about link dependencies. So
I'd have to have e.g. a variable.... I thought that a `-libraries` static
library containing no symbols of its own is cleaner. (The library will actually
have to contain something due to the macOS error I mentioned above.)
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> Do not build separate libqpid-dispatch.so
> -----------------------------------------
>
> Key: DISPATCH-2178
> URL: https://issues.apache.org/jira/browse/DISPATCH-2178
> Project: Qpid Dispatch
> Issue Type: Improvement
> Affects Versions: 1.16.0
> Reporter: Jiri Daněk
> Assignee: Jiri Daněk
> Priority: Major
>
> h3. Motivation
> The split into a binary and a library is not unprecedented (e.g. CPython does
> exactly the same thing), but in Dispatch it is avoidable with minimal code
> changes (an executable can {{dlopen(NULL, ...)}} itself.
> Getting rid of libqpid-dispatch.so will mean one less file that we need to
> install (and since it is not a published API, finding a good place for the so
> has been tricky in the past (see DISPATCH-194).
> Furthermore, avoiding the indirection of a library call will likely give some
> performance benefit at a low level (individual function calls) similar to
> (again) Python in https://fedoraproject.org/wiki/Changes/PythonStaticSpeedup.
> The gains can be best utilized after doing LTO (see DISPATCH-2121).
> h3. Expected issues
> The problem with this is that we lose semantic interposition
> (https://fedoraproject.org/wiki/Changes/PythonNoSemanticInterpositionSpeedup),
> meaning we won't be able to simply override symbols from libqpid-dispatch.so
> at runtime. This is an issue because Dispatch unittests depend on this. (See
> DISPATCH-1783)
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