CMake fails when $NTA and $NUPIC are both empty #755
Description
In README.md:
After CMake generation, two useful environment variables will be created:
- $NUPIC, which is the same as $REPOSITORY
- $NTA, which references $HOME/nta/eng (the directory with all executables and libraries generated from build process). If this variable is already set, the $REPOSITORY/release will not be created, and $NTA will be used as the release directory.
This is an usability improvement compared to the old "set $NUPIC and $NTA yourself or the build fails" approach, providing sane defaults in the spirit of 2014 Goals For NuPIC: Easy install, easy build.
But when $NTA and $NUPIC are both empty, cmake $REPOSITORY complains:
CMake Error at CMakeLists.txt:181 (message):
$NTA environment variable cannot be the same as the $NUPIC environment
variable!
-- Configuring incomplete, errors occurred!
In CMakeLists.txt:181, it reads:
#
# Cannot have same $NTA and $NuPIC
#
if("$ENV{NTA}" STREQUAL "$ENV{NUPIC}")
message(FATAL_ERROR "\$NTA environment variable cannot be the same as the \$NUPIC environment variable!")
endif()
This logic fixes #659 , but is in contradiction to with the statements in README.md, which implemented around CMakeLists.txt:436:
set_environment_variable(NUPIC "${PROJECT_SOURCE_DIR}" OFF)
...
if("$ENV{NTA}" STREQUAL "")
set_environment_variable(NTA "${CMAKE_INSTALL_PREFIX}" OFF)
Thus, as long as they are not both empty, defaults would work.
And I noticed in .travis.yml, $NUPIC and $NTA are declare in env.global, and I guess most nupic developers already have them configured, that's why it's not spotted.