[CMake] project directive overwrites CMAKE_INSTALL_PREFIX?

[Chris Johnson]

I have a global include file used by all of the CMakeLists.txt files in my
project. In it, I set the value of CMAKE_INSTALL_PREFIX, as well as a
number of other variables and functions.

In my CMakeLists.txt file, I had this:

cmake_minimum_require(VERSION 2.8.4)
include(global.inc)
project(whatever)

When I run cmake, the value of CMAKE_INSTALL_PREFIX is lost! Instead, in
the resulting cmake_install.cmake file has been defaulted back to
/usr/local which is completely wrong.

However, if I change the order to this:

cmake_minimum_require(VERSION 2.8.4)
project(whatever)
include(global.inc)

It appears to work.

I find nothing in the documentation saying that the project() directive
will set CMAKE_INSTALL_PREFIX.

Even more strangely, if I run cmake a second time with the first
configuration (include before project), it will rewrite cmake_install.cmake
with the correct value.
​ ​
That is, the behavior of cmake appears to be different based on whether the
build directory is empty or already contains cmake_install.cmake and
CMakeCache.txt files
​, even though they contain the wrong path value for CMAKE_INSTALL_PREFIX.​

What is going on here?
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