YouCompleteMe won't compile on Slackware14.2

I am trying to compile YouCompleteMe for vim. When I ran install.py, I got this error

Code:Searching Python 3.7 libraries...
Found Python library: /usr/lib64/libpython3.7m.so
Found Python headers folder: /usr/include/python3.7m
-- The C compiler identification is GNU 5.5.0
-- The CXX compiler identification is GNU 5.5.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
CMake Error at CMakeLists.txt:232 (message):
Your C++ compiler does NOT fully support C++17.

-- Configuring incomplete, errors occurred!
See also "/tmp/ycm_build_s90xbc7b/CMakeFiles/CMakeOutput.log".
ERROR: the build failed.

NOTE: it is *highly* unlikely that this is a bug but rather
that this is a problem with the configuration of your system
or a missing dependency. Please carefully read CONTRIBUTING.md
and if you're sure that it is a bug, please raise an issue on the
issue tracker, including the entire output of this script
and the invocation line used to run it.The log file above doesn't exist