Fix undefined symbol error around SharedCtor() #8827
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NB: the same problem applies to SharedDtor() though it is not broken in our case. |
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@georgthegreat Would you mind running |
Apparently, protocolbuffers#8532 was incorrect if applied to 3.17.x branch. 3.17.x changed code generation to mark `SharedCtor()` and `SharedDtor()` as inline in .pb.cc. It looks like we have a compile-time undefined behavior in C++ now. As cppreference.com [says](https://en.cppreference.com/w/cpp/language/inline): _The definition of an inline function <...> must be reachable in the translation unit where it is accessed (not necessarily before the point of access)._ As protobuf allows custom plugins to generate custom code, there is no limitation on where SharedCtor couble be possible referenced from. In our case we have SharedCtor invoked from corresponding `.pb.h` code, thus triggering: ``` ld: error: undefined symbol: package::Message::SharedCtor()` >>> referenced by file.pb.h:$$$$ ``` If this patch is not applicable, I can take a look into changing the code generation, but doing this will be harder then removing _inline_.
georgthegreat
commented
Jul 20, 2021
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@deannagarcia, @acozzette, can we proceed with merging of this PR? |
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Apparently, #8532 was incorrect if applied to 3.17.x branch.
3.17.x changed code generation to mark
SharedCtor()andSharedDtor()as inline in .pb.cc.It looks like we have a compile-time undefined behavior in C++ now. As cppreference.com says:
The definition of an inline function <...> must be reachable in the translation unit where it is accessed (not necessarily before the point of access).
As protobuf allows custom plugins to generate custom code, there is no limitation on where SharedCtor couble be possible referenced from. In our case we have SharedCtor invoked from corresponding
.pb.hcode, thus triggering:If this patch is not applicable, I can take a look into changing the code generation, but doing this will be harder than removing inline.