CMake non-configurable option-CodePudding

In CMake, how can I define an option that is not configurable by the user, but automatically calculated?

I would like to do the following:

if (FOO AND NOT BAR)
    option(BOO "Foo and not bar" ON)
endif()

And then I can use BOO in different CMake files:

if (BOO)
    # do something
endif()

And also in sources:

#ifdef BOO
// do something
#endif

So BOO behaves like a regular option, but is automatically calculated and not configurable by user running cmake.

EDIT: I now realize that options are not implicitly available in sources, but need to be defined explicitly with target_add_definitions or other means. So now it becomes obvious that the solution is to define BOO as a CMake variable, rather than an option.

CodePudding user response：

Your "non-user-configurable" option sounds like a variable, which you can create like:

if(FOO AND NOT BAR)
  set(BOO TRUE)
else()
  set(BOO FALSE)
endif()

To use this variable in C code, you need to tell CMake to create a C file which defines this information. Take a look at CMake's configure_file function. Here's the official documentation, and here's part of the official CMake tutorial which walks through a simple usage of this function. I would type out some example code, but it would be a lot of boilerplate, and the linked documents do the job and should be better at answering your questions.

CodePudding user response：

You can just use variable with set(BOO <what you want>).

You can find the documentation here: https://cmake.org/cmake/help/latest/command/set.html

But there is no option that will restrict the value of your variable for an internal settings. Only you.