Linker errors on clang 7.0.1 on Linux

[luxuki]

I built cppkafka (v0.3.0 release) with:

CPPKAFKA_BUILD_SHARED OFF
CPPKAFKA_RDKAFKA_STATIC_LIB ON

cppkafka build was successful.

Tried building consumer_dispatcher_example.cpp. Works on g++ 8.1.0 but when built (both the example and cppkafka) with clang++7.0.1 it cannot find a few symbols from librdkafka.a:

.../cppkafka/lib/libcppkafka.a(error.cpp.o): In function `cppkafka::Error::to_string[abi:cxx11]() const':
.../cppkafka/src/error.cpp:48: undefined reference to `rd_kafka_err2str'
.../cppkafka/lib/libcppkafka.a(metadata.cpp.o): In function `Metadata':
.../cppkafka/src/metadata.cpp:128: undefined reference to `rd_kafka_metadata_destroy'

Any idea why that might be happening?

[mfontanini]

How are you building the example? By running make examples?

[luxuki]

I was building it directly passing files into compiler (without a Makefile). Did couple more checks - it seems to be not working with either g++ or clang++ as long as optimisation mode is less than O2. Works perfectly fine with O2 and O3, cannot find the symbols if built with O0 or O1.
Very strange.

[mfontanini]

Are you linking with rdkafka? Because that would do it.

[csfreebird]

use 'ldd your_binary' command, see the output.