CMAKE_PREFIX_PATH and /usr/local

[Tomasz CEDRO]

On Fri, Jan 15, 2021 at 10:05 AM Gleb Popov wrote:
> On Fri, Jan 15, 2021 at 12:50 AM Tomasz CEDRO wrote:
>> Hello world :-)
>> I am porting LimeSuite to FreeBSD. Local patch fixes missing
>> "/usr/local/" path in CMakeLists.txt so the package now builds fine on
>> FreeBSD. On Linux probably most of the libraries and includes are
>> located in /usr/ do problem does not exist.
>> Upstream has some objections to accept this patch and considers
>> "/usr/local" a non-standard path [1]. But they propose to use
>> CMAKE_PREFIX_PATH to add "/usr/local". This however does not seem to
>> be supported in Ports (yet?).
>> The question is how to tell CMake about "/usr/local/include" without
>> source code modification? :-)
>> Below is the proposed patch:
>> > @@ -171,6 +171,11 @@ if (ENABLE_NEW_GAIN_BEHAVIOUR)
>>      add_definitions(-DNEW_GAIN_BEHAVIOUR)
>>  endif()
>> +if (CMAKE_SYSTEM_NAME MATCHES "BSD")
>> +    include_directories("/usr/local/include")
>
> This is most certainly a wrong thing to do. Instead of simply adding -I/usr/local/include everywhere, you should fix problems for each dependency that the software requires.
>
> What error do you get without your patch?

Hello Gleb :-) This seems the LimeSuite CMake issue not to use
/usr/local/include where some GL includes are located. Without it
there is a build problem as GL.h (something like this) is not found. I
am not sure it this is the only occurrence of this symptom. Simply
adding /usr/local/include solves the problem.

Accorging to cmake 3.19 documentation CMAKE_PREFIX_PATH is empty by
default and it needs to be filled with search paths by the project:

CMAKE_PREFIX_PATH is empty by default, so the project sets the value,
so the /usr/local is missing now and should be put here (but still in
the source code so the patch seems unavoidable):
https://cmake.org/cmake/help/latest/variable/CMAKE_PREFIX_PATH.html?highlight=cmake_prefix_path

We are back in the point either to fix the upstream and add
"/usr/local" into CMAKE_PREFIX_PATH or propagate is somehow from a
port anyhow..?

Thanks :-)
Tomek

-- 
CeDeROM, SQ7MHZ, http://www.tomek.cedro.info