CPACK variables are set even when PAHO_ENABLE_CPACK is turned off

[JeroenBrunnenkreef]

Some CPACK variables are set even when the PAHO_ENABLE_CPACK option is turned off. This is a problem when the CMake project is included into another CMake project (as a sub-project).

To Reproduce

• Include paho-mqtt in another CMake project.
• set(PAHO_ENABLE_CPACK OFF)
• CPACK variables, for example CPACK_GENERATOR, are set/overridden by paho-mqtt.

Expected behavior
CPACK variables are not set when PAHO_ENABLE_CPACK is turned off.

Environment (please complete the following information):

• OS: Linux
• Version 1.5.3

Possible solution
This can probably be fixed by wrapping the CPACK parts with an if (PAHO_ENABLE_CPACK) in the files:

• CMakeLists.txt
• externals/paho-mqtt-c/CMakeLists.txt

[fpagliughi]

That makes sense.

Our externals/paho-mqtt-c is just a Git submodule for the Paho C library. So we'd need to fix it in that library also. I'll make a ticket in that repo.

[JeroenBrunnenkreef]

Thanks.

[fpagliughi]

I realized that the PAHO_ENABLE_CPACK option isn't even in this library! (I didn't write the original CMake build).

So CPack was essentially always enabled in this library, and only reflected as a possible option when configuring to build the C library (i.e. PAHO_WITH_MQTT_C=ON).

So I added the option here, defaulted to TRUE to maintain backward compatibility, so you can now disable it when building just this library.

I also sent a PR to the C lib to fix the problem there as well. Hopefully it will make it into the next release there.
eclipse-paho/paho.mqtt.c#1665