How to list all CMake build options and their default values?

cmake -LAH

To list all option(...) and set(... CACHE ...) variables, including those marked as advanced, do:

cmake -LAH

where:

• -L: list variables

• -A: include advanced variables.

  CMake marks most but not all of its default pre-defined variables as, and you can mark you own variables as advanced with mark_as_advanced). Some default CMake advanced variables include basic default compilation parameters such as:

  CMAKE_CXX_COMPILER:FILEPATH=/usr/bin/c++
  CMAKE_CXX_FLAGS:STRING=
  CMAKE_CXX_FLAGS_DEBUG:STRING=-g
  

  If you are only interested in the main configuration options of some project, you will likely want to remove the -A as it would be mostly noise.

• -H: include the help strings as // My help above each setting. -H was previously mentioned at: https://stackoverflow.com/a/53075317/895245 consider upvoting that answer

Example

CMakeLists.txt

cmake_minimum_required(VERSION 3.0)
project(ProjectName)
set(GREETING "hello" CACHE STRING "How to greet")
set(GREETING2 "hello2" CACHE STRING "Supersecret greeting")
mark_as_advanced(FORCE VAR GREETING2)
set(MYNOCACHE "mynocacheval")
option(WORLD "Print world or not?" ON)

If we run:

mkdir -p build
cd build
cmake -LAH ..

the output contains:

// How to greet
GREETING:STRING=hello

// Supersecret greeting
GREETING2:STRING=hello2

// How to greet
MSG:STRING=hello

// Supersecret greeting
MSG2:STRING=hello2

// Print world or not?
WORLD:BOOL=ON

plus a bunch of default defined CMake variables. If we remove -A we get only:

// Choose the type of build, options are: None Debug Release RelWithDebInfo MinSizeRel ...
CMAKE_BUILD_TYPE:STRING=debug

// Install path prefix, prepended onto install directories.
CMAKE_INSTALL_PREFIX:PATH=/usr/local

// How to greet
GREETING:STRING=hello

// How to greet
MSG:STRING=hello

// Print world or not?
WORLD:BOOL=ON

so we see that our advanced variable GREETING2 is not present. We also understand that CMake feels that two of their default variables are often useful to merit the non-advanced distinction:

• CMAKE_BUILD_TYPE to control debug vs release: Debug vs Release in CMake
• CMAKE_INSTALL_PREFIX to decide where to install the project output

Without -H we get just:

CMAKE_BUILD_TYPE:STRING=debug
CMAKE_INSTALL_PREFIX:PATH=/usr/local
GREETING:STRING=hello
MSG:STRING=hello
WORLD:BOOL=ON

Note that the values are the cached values, not the defaults. E.g. if we first set a cached value:

cmake -DGREETING=bye ..

then running again cmake -L .. gives:

CMAKE_BUILD_TYPE:STRING=debug
CMAKE_INSTALL_PREFIX:PATH=/usr/local
GREETING:STRING=bye
MSG:STRING=hello
WORLD:BOOL=ON

Better way to determine the exact build options: run a verbose build!

I think some of people coming to this question are trying to understand how CMake is building their things exactly.

While you could deduce much of that from cmake -LA, a better more direct and sure-fire way would be as per: Using CMake with GNU Make: How can I see the exact commands? to just build with with:

make VERBOSE=1

The output would then contain a line of type:

/usr/bin/cc -DGREETING=\"hello\" -DWORLD -MD -MT CMakeFiles/main.dir/main.c.o -MF CMakeFiles/main.dir/main.c.o.d -o CMakeFiles/main.dir/main.c.o -c /home/ciro/main.c

which makes it clear exactly what CMake is doing.

ccmake ncurses

ccmake is an nCurses Cmake UI. The advantage over cmake -L is that you can interactively set the values as you find them:

sudo apt-get install cmake-curses-gui
ccmake .

shows:

To see the advanced options from cmake-curses-gui you can just enter the t key as mentioned on the UI which toggles them on or off.

cmake-gui

This UI is a bit better than ccmake in terms of capabilities:

sudo apt install cmake-qt-gui
cmake-gui .

we have:

• “Advanced” checkbox to show the advanced options
• “Grouped” checkbox to group options. By default it produces two categories:
  • “CMAKE” for the “CMAKE” default options
  • “Ungrouped Entries” for your variables
    Option groups are apparently generated automatically based on common option name prefixes: Creating groups of CMake options

Tested in Ubuntu 22.10, cmake 3.5.2.