[bmv2] path fixes for finding BMv2

[grg]

Two changes for finding BMv2:

• Remove "build" from the search paths. BMv2 targets are built in behavioral-model/targets/... and not in behavioral-model/build/targets/...
• Correct search path variable name in pna_nic error message.

Is there any env where BMv2 targets are built in build/targets? The README.md instructions always build in targets.

[jafingerhut]

It looks like these are paths searching for simple_switch and/or simple_switch_grpc executable programs on the system where p4c is being built?

And I guess the purpose is to run those programs for the subset of backend BMv2 tests that run the BMv2 software switch, e.g. the BMv2 P4 programs that have STF tests checked in?

I often run such tests on Ubuntu Linux systems that I install BMv2 and p4c from source, but I also always install the simple_switch and simple_switch_grpc executables in my /usr/local/bin directory, so might never have run the tests in a scenario where the paths you are changing here failed to find those executables.

[grg]

It looks like these are paths searching for simple_switch and/or simple_switch_grpc executable programs on the system where p4c is being built?

And I guess the purpose is to run those programs for the subset of backend BMv2 tests that run the BMv2 software switch, e.g. the BMv2 P4 programs that have STF tests checked in?

I often run such tests on Ubuntu Linux systems that I install BMv2 and p4c from source, but I also always install the simple_switch and simple_switch_grpc executables in my /usr/local/bin directory, so might never have run the tests in a scenario where the paths you are changing here failed to find those executables.

Yes, I believe this is for the case where the programs are compiled but not installed. Potentially useful for developers who don't want to have to do an install each time they rebuild the model 🙂

The cmake find_program documentation describes what additional paths are searched, in addition to those passed in via the PATHS parameter. Since we don't pass in parameters include NO_DEFAULT_PATH and NO_SYSTEM_ENVIRONMENT_PATH, it ends up searching the directories set in your environment.

[fruffy]

Kind of hacky but not worse than before...
These path hints should probably be an option you can pass to CMake.

[grg]

I'm happy to clean this up a little before merging.

Here are a couple of possibilities for how change the set statement:

set(BMV2_SIMPLE_SWITCH_SEARCH_PATHS
  ${CMAKE_INSTALL_PREFIX}/bin)
  ${BMV2_SOURCE_DIR}/targets/simple_switch)

set(BMV2_SIMPLE_SWITCH_SEARCH_PATHS
  ${CMAKE_INSTALL_PREFIX}/bin)
if(DEFINED BMV2_SOURCE_DIR)
  set(BMV2_SIMPLE_SWITCH_SEARCH_PATHS
    ${BMV2_SIMPLE_SWITCH_SEARCH_PATHS}
    ${BMV2_SOURCE_DIR}/targets/simple_switch )
endif()

The first is simple and easy to read, but it has the downside of searching /targets/simple_switch if BMV2_SOURCE_DIR is set. The second is quite a bit more verbose but it avoids adding a phantom search directory when BMV2_SOURCE_DIR it not set.

Do you have a preference? Or do you have an alternative style suggestion?

[fruffy]

Second option sounds good to me.

[grg]

I've pushed a new commit that implements this.