memory leaks reported by valgrind when otlp http exporter is used

[farzinlize]

Even though I call tracerProvider->shutdown() at the end of my app, valgrind reports many memory leaks related to otlp exporter (libgnutlsm, google protobuf and such). There is no leak when using the same app with OStreamSpanExporter instead. For cleanup, I set an empty TracerProvider just like examples and before that, I called provider->ForceFlush and provider->Shutdown using the exact pointer I created when setting up the TracerProvider in initial phase. it complies and in runtime I see no errors. I also confirmed that shutdown method and forceFlush method returning 1(true) so I guessed it means no error.

please guide me how to implement a good cleanup function for OpenTelemetryC++ library so no error and memory leak problem appears on valgrind report. (I don't want to suppress such errors in valgrind report, ChatGPT already suggested that)

==35931== LEAK SUMMARY:
==35931==    definitely lost: 0 bytes in 0 blocks
==35931==    indirectly lost: 0 bytes in 0 blocks
==35931==      possibly lost: 0 bytes in 0 blocks
==35931==    still reachable: 120,567 bytes in 890 blocks
==35931==         suppressed: 0 bytes in 0 blocks

I noticed the 120,567 bytes stays the same in many reports

here is some example errors from valgrind report:

...

==35931== 360 bytes in 5 blocks are still reachable in loss record 121 of 130
==35931==    at 0x4846FA3: operator new(unsigned long) (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==35931==    by 0x4BC2DD2: google::protobuf::EncodedDescriptorDatabase::DescriptorIndex::AddSymbol(google::protobuf::stringpiece_internal::StringPiece) (in /usr/lib/x86_64-linux-gnu/libprotobuf.so.32.0.12)
==35931==    by 0x4BC43B1: google::protobuf::EncodedDescriptorDatabase::Add(void const*, int) (in /usr/lib/x86_64-linux-gnu/libprotobuf.so.32.0.12)
==35931==    by 0x4B66C76: google::protobuf::DescriptorPool::InternalAddGeneratedFile(void const*, int) (in /usr/lib/x86_64-linux-gnu/libprotobuf.so.32.0.12)
==35931==    by 0x4BDBB77: ??? (in /usr/lib/x86_64-linux-gnu/libprotobuf.so.32.0.12)
==35931==    by 0x4AE02BD: ??? (in /usr/lib/x86_64-linux-gnu/libprotobuf.so.32.0.12)
==35931==    by 0x400571E: call_init.part.0 (dl-init.c:74)
==35931==    by 0x4005823: call_init (dl-init.c:120)
==35931==    by 0x4005823: _dl_init (dl-init.c:121)
==35931==    by 0x401F59F: ??? (in /usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2)

...

==35931== 1,411 bytes in 65 blocks are still reachable in loss record 126 of 130
==35931==    at 0x4846828: malloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==35931==    by 0x60DAB67: ??? (in /usr/lib/x86_64-linux-gnu/libtasn1.so.6.6.3)
==35931==    by 0x60E28B7: asn1_array2tree (in /usr/lib/x86_64-linux-gnu/libtasn1.so.6.6.3)
==35931==    by 0x5472339: ??? (in /usr/lib/x86_64-linux-gnu/libgnutls.so.30.37.1)
==35931==    by 0x5438EDF: ??? (in /usr/lib/x86_64-linux-gnu/libgnutls.so.30.37.1)
==35931==    by 0x400571E: call_init.part.0 (dl-init.c:74)
==35931==    by 0x4005823: call_init (dl-init.c:120)
==35931==    by 0x4005823: _dl_init (dl-init.c:121)
==35931==    by 0x401F59F: ??? (in /usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2)
...

[paulfloyd]

==35931== by 0x4005823: _dl_init (dl-init.c:121)

^^^ these are all objects with static lifetime (like file static/global objects).

[owent]

Please call ::google::protobuf::ShutdownProtobufLibrary() after all protobuf users, including otel-cpp’s OTLP exporters, have shut down.