Currently, grpc depends on the full host-grpc, which in turn depends on host
versions of many other libraries. One of these, host-libabseil-cpp, also
requires a host gcc 4.9 or larger, a dependency which is not met on CentOS
7.
But in fact, the target grpc only needs the 'grpc_cpp_plugin' binary from
host-grpc. And that binary does not depend on host-libabseil-cpp or other
libraries, only on host-protobuf.
Given the above, simplify the grpc/host-grpc situation.
- Add a patch to the (host-)grpc CMakeLists.txt file to add an option to
only build grpc_cpp_plugin.
- Update grpc.mk and Config.in to remove the unnecessary dependencies, and
change the host-grpc configure options to make cmake happy.
The advantages of these changes are:
- making grpc available to older hosts with gcc < 4.8, like CentOS 7
- significantly reducing the build time of host-grpc and its dependencies
The patch was proposed upstream but not accepted with below rationale.
Perhaps input from others can help in persuading upstream in a future
attempt.
'What you're doing sounds like quite a narrow use case. But we simply
cannot provide a cmake option for every possible scenario in the world.
Introducing a new cmake option isn't for free and requires careful
design and maintenance.'
Nevertheless, given the benefits in terms of build time and dependency
reduction, it makes sense to apply this patch in spite of the disadvantage
of a local non-upstreamed patch.
Signed-off-by: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
[Arnout: propagate removed dependency to collectd]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
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