What is CMakeCache.txt and why it overrides my variables

Question

As I am using cmake after editing CMakeLists.txt some variables wouldn\'t be loaded. If I had something defined with CACHE STRING it wouldn\'t let me to change it without forcin

Answer 1

Motivating example

This is basically what https://stackoverflow.com/a/42160304/895245 mentions, but with a more explicit example to make it easier to understand.

Consider this use case:

git clone project
cd project
# Options ddfined with "option(" in CMakeLists.txt.
cmake -DOPT1=ON -DOPT2=OFF -DOPT3=ON .
make
# Create bugs (edit code).
make

Then, a few days later, a new directory is added to the project.

This means CMakeLists.txt was changed with a new add_subdirectory, and so we have to run cmake again to update our make files.

If we didn't have CMakeCache.txt, we would have to remember and type all options again:

git pull
cmake -DOPT1=ON -DOPT2=OFF -DOPT3=ON .
make

But because of the cache, we can do just:

cmake .
make