My project contains a custom target which generates some output via .cmake script. It looks like this:
add_custom_target(TargetName
COMMAND ${CMAKE_COMMAND} -P ${CMAKE_SOURCE_DIR}/cmake/script.cmake
BYPRODUCTS ${CMAKE_CURRENT_BINARY_DIR}/generated/output
WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
VERBATIM
)
But now I want to set come cache variables inside the script. I tried doing like that:
message("MY_CACHE_VARIABLE = ${MY_CACHE_VARIABLE}")
set(MY_CACHE_VARIABLE "VALUE" CACHE INTERNAL "")
And I faced with the problem that cache variables are not saved. It always prints me empty output:
MY_CACHE_VARIABLE =
I already tried setting working directory as CMAKE_BINARY_DIR, or passing CMAKE_BINARY_DIR of the last argument of cmake command, or passing -B ${CMAKE_BINARY_DIR} or -C ${CMAKE_BINARY_DIR}/CMakeCache.txt as arguments and etc. None of these worked.
So is there any way to reuse existing cache inside CMake subprocess or I just should write my own cache inside the script?
You have to distinguish between running CMake to generate build files (for Make, Ninja, etc.) and running CMake in script mode:
Script mode simply runs the commands in the given CMake Language source file and does not generate a build system. It does not allow CMake commands that define build targets or actions.
-- cmake-language(7)
No configure or generate step is performed and the cache is not modified.
-- cmake(1)
So in script mode (-P), CMake is not aware of the cache or any variable/target/etc. defined in your regular CMakeLists.txt files. It is more similar to executing a bash/shell script than to processing a "usual" CMakeLists.txt.
But don't worry, there is still a solution to your problem. You can simply pass your arguments as -D options to your script:
add_custom_target(TargetName
COMMAND ${CMAKE_COMMAND}
-DMY_VAR="..."
-DANOTHER_VAR="..."
-P ${CMAKE_SOURCE_DIR}/cmake/script.cmake
...
)
Note however:
If variables are defined using -D, this must be done before the -P argument.
-- cmake(1)
Every time I get a different source directory, and I have a fixed build directory. Every time I will run cmake /path/to/project and run ninja. It will report an error : Make Error: The source "/path1/to/project/CMakeLists.txt" does not match the source "/path2/to/project/CMakeLists.txt" used to generate cache. Re-run cmake with a different source directory.
So what I did was manually change the options related to the path of project in the CMakeCache.txt. The result is that it will compile the project from scratch every time instead of incrementally compiling, So is there any feasible way to achieve incremental compilation or in this case it is impossible to achieve incremental compilation ？
Mount the source directory always to a same constant absolute location. On Linux, you could use mount namespaces, for example use proot.
proot -b /path/to/project:/work -w /work cmake -B builddir -S .
proot -b /path/to/project:/work -w /work cmake --build builddir
I have a project that has the following folder structure:
src/
|
|- foo/config.ini
|- bar/config.ini
|- tool/
| | - myscript.sh
| | - CMakeLists.txt
|- cpp/
|- main.cpp
|- baz.cpp
|- CMakeLists.txt
Basically, I want to
Have a custom target make foo-target
I want foo-target to depend on my executable built in cpp/main.cpp
I want foo-target to somehow configure myscript.sh
myscript.sh is configured so that it knows where to find foo/config.ini (something like having the absolute path to the ini)
myscript.sh is also configured so that it knows where to find the executable built in cpp/main.cpp
I have looked into:
add_custom_command
add_custom_target
configure_file
Exporting variables to the environment (via add custom command)
But I just can't figure out how to! And could use some help!
Maybe there are other CMake commands that could help or maybe I am trying something silly that I shouldn't do, any help is appreciated!
For CMake version 3.4 and above
Edit:
Here is an example for myscript.sh
#!/bin/sh
CONFIG_INI=#CONFIG_INI_ABS_PATH#
EXE_PATH=#EXE_ABS_PATH#
echo "Config path is $CONFIG_INI"
echo "Exe path is $EXE_PATH"
As for the CMakeLists.txt under tools
set (CONFIG_INI_ABS_PATH ${PROJECT_SOURCE_DIR}/foo/config.ini)
set (EXE_ABS_PATH ${PROJECT_SOURCE_DIR}/cpp/myExe)
# This works, but how can I make it depend on myExe
# And how can I configure it "on command" (i.e. make foo-target)
configure_file(myscript.sh myscript.sh
USE_SOURCE_PERMISSIONS
#ONLY
)
# Can't figure out how to use this one
add_custom_command(OUTPUT myscript.sh
# COMMAND use sed to modify the bash script? by cahcing all #*# to what I want?
)
add_custom_target(foo-target
DEPENDS myExe # I know that I need this to make my target depend on "myExe"
)
Pass options as arguments to scripts:
#!/bin/sh
config_ini=$1
exe_path=$2
echo "Config path is $config_ini"
echo "Exe path is $exe_path"
Use generator expression to get path to file of executable. Assuming your script does not generate anything, you could:
add_executable(my_exe ...)
find_program(SHELL sh REQUIRED)
add_custom_target(foo-target
COMMENT "Print two lines"
COMMAND
${SHELL}
${CMAKE_CURRENT_SOURCE_DIR}/script.sh
${CMAKE_CURRENT_SOURCE_DIR}/foo/config.ini
$<TARGET_FILE:my_exe>
DEPENDS
${CMAKE_CURRENT_SOURCE_DIR}/script.sh
${CMAKE_CURRENT_SOURCE_DIR}/foo/config.ini
$<TARGET_FILE:my_exe>
VERBATIM
)
Do not use make target_name. Prefer to use cmake --build build_dir --target target_name, so that when you switch to a lot times faster Ninja you will not have to change your scripts.
I have a problem with the global environmental variable CMAKE_PREFIX_PATH. I already set this and I can see it is set when I type env, but when I run cmake . to build HipHop, it tells me that the variable isn't set.
Is there a way I can hard-code this into the makefiles?
Try to run cmake -DCMAKE_PREFIX_PATH=/your/path .
CMAKE_PREFIX_PATH works as a build directive, rather than as an environment variable. Moreover, you may perform the build into a dedicated temporary directory (it's cleaner, because when done, you can remove that temporary directory and you get back a clean pristine source tree).
$ mkdir -p tmpbuild && cd tmpbuild
$ cmake -DCMAKE_PREFIX_PATH=~/deliveries/hiphop ..
$ make install
$ cd ..
On MacOS it's different. I had to use:
make -i CMAKE_PREFIX_PATH="/the/path"
This was while installing VMQT, and this error was shown:
CMake Error at CMakeLists.txt:87 (find_package): By not providing
"FindOpenCV.cmake" in CMAKE_MODULE_PATH this project has asked CMake
to find a package configuration file provided by "OpenCV", but CMake
did not find one.
Could not find a package configuration file provided by "OpenCV"
with any of the following names:
OpenCVConfig.cmake
opencv-config.cmake
Add the installation prefix of "OpenCV" to CMAKE_PREFIX_PATH or set
"OpenCV_DIR" to a directory containing one of the above files. If
"OpenCV" provides a separate development package or SDK, be sure it
has been installed.
Used this to solve it: make -i CMAKE_PREFIX_PATH="/opt/homebrew/Cellar/opencv/4.6.0_1/lib/cmake/opencv4/"
I do cmake . && make all install. This works, but installs to /usr/local.
I need to install to a different prefix (for example, to /usr).
What is the cmake and make command line to install to /usr instead of /usr/local?
You can pass in any CMake variable on the command line, or edit cached variables using ccmake/cmake-gui. On the command line,
cmake -DCMAKE_INSTALL_PREFIX:PATH=/usr . && make all install
Would configure the project, build all targets and install to the /usr prefix. The type (PATH) is not strictly necessary, but would cause the Qt based cmake-gui to present the directory chooser dialog.
Some minor additions as comments make it clear that providing a simple equivalence is not enough for some. Best practice would be to use an external build directory, i.e. not the source directly. Also to use more generic CMake syntax abstracting the generator.
mkdir build && cd build && cmake -DCMAKE_INSTALL_PREFIX:PATH=/usr .. && cmake --build . --target install --config Release
You can see it gets quite a bit longer, and isn't directly equivalent anymore, but is closer to best practices in a fairly concise form... The --config is only used by multi-configuration generators (i.e. MSVC), ignored by others.
The ":PATH" part in the accepted answer can be omitted. This syntax may be more memorable:
cmake -DCMAKE_INSTALL_PREFIX=/usr . && make all install
...as used in the answers here.
Note that in both CMake and Autotools you don't always have to set the installation path at configure time. You can use DESTDIR at install time (see also here) instead as in:
make DESTDIR=<installhere> install
See also this question which explains the subtle difference between DESTDIR and PREFIX.
This is intended for staged installs and to allow for storing programs in a different location from where they are run e.g. /etc/alternatives via symbolic links.
However, if your package is relocatable and doesn't need any hard-coded (prefix) paths set via the configure stage you may be able to skip it.
So instead of:
cmake -DCMAKE_INSTALL_PREFIX=/usr . && make all install
you would run:
cmake . && make DESTDIR=/usr all install
Note that, as user7498341 points out, this is not appropriate for cases where you really should be using PREFIX.
The way I build CMake projects cross platform is the following:
/project-root> mkdir build
/project-root> cd build
/project-root/build> cmake -G "<generator>" -DCMAKE_INSTALL_PREFIX=stage ..
/project-root/build> cmake --build . --target=install --config=Release
The first two lines create the out-of-source build directory
The third line generates the build system specifying where to put the installation result (which I always place in ./project-root/build/stage - the path is always considered relative to the current directory if it is not absolute)
The fourth line builds the project configured in . with the buildsystem configured in the line before. It will execute the install target which also builds all necessary dependent targets if they need to be built and then copies the files into the CMAKE_INSTALL_PREFIX (which in this case is ./project-root/build/stage. For multi-configuration builds, like in Visual Studio, you can also specify the configuration with the optional --config <config> flag.
The good part when using the cmake --build command is that it works for all generators (i.e. makefiles and Visual Studio) without needing different commands.
Afterwards I use the installed files to create packages or include them in other projects...
Starting with CMake 3.15, the correct way of achieving this would be using:
cmake --install <dir> --prefix "/usr"
Official Documentation
Starting with CMake 3.21 you can use the --install-prefix option instead of manually setting CMAKE_INSTALL_PREFIX.
The modern equivalent of configure --prefix=DIR && make all install would now be:
cmake -B build --install-prefix=DIR
cmake --build build
cmake --install build
Regarding Bruce Adams answer:
Your answer creates dangerous confusion. DESTDIR is intended for
installs out of the root tree. It allows one to see what would be
installed in the root tree if one did not specify DESTDIR.
PREFIX is the base directory upon which the real installation is
based.
For example, PREFIX=/usr/local indicates that the final destination
of a package is /usr/local. Using DESTDIR=$HOME will install the files
as if $HOME was the root (/). If, say DESTDIR, was /tmp/destdir, one
could see what 'make install' would affect. In that spirit, DESTDIR
should never affect the built objects.
A makefile segment to explain it:
install:
cp program $DESTDIR$PREFIX/bin/program
Programs must assume that PREFIX is the base directory of the final
(i.e. production) directory. The possibility of symlinking a program
installed in DESTDIR=/something only means that the program does not
access files based upon PREFIX as it would simply not work. cat(1)
is a program that (in its simplest form) can run from anywhere.
Here is an example that won't:
prog.pseudo.in:
open("#prefix#/share/prog.db")
...
prog:
sed -e "s/#prefix#/$PREFIX/" prog.pseudo.in > prog.pseudo
compile prog.pseudo
install:
cp prog $DESTDIR$PREFIX/bin/prog
cp prog.db $DESTDIR$PREFIX/share/prog.db
If you tried to run prog from elsewhere than $PREFIX/bin/prog,
prog.db would never be found as it is not in its expected location.
Finally, /etc/alternatives really does not work this way. There are
symlinks to programs installed in the root tree (e.g. vi -> /usr/bin/nvi,
vi -> /usr/bin/vim, etc.).
It is considered bad practice to invoke the actual build system (e.g. via the make command) if using CMake. It is highly recommended to do it like this:
Configure + Generation stages:
cmake -S foo -B _builds/foo/debug -G "Unix Makefiles" -D CMAKE_BUILD_TYPE:STRING=Debug -D CMAKE_DEBUG_POSTFIX:STRING=d -D CMAKE_INSTALL_PREFIX:PATH=/usr
Build and Install stages:
cmake --build _builds/foo/debug --config Debug --target install
When following this approach, the generator can be easily switched (e.g. -G Ninja for Ninja) without having to remember any generator-specific commands.
Note that the CMAKE_BUILD_TYPE variable is only used by single-config generators and the --config argument of the build command is only used by multi-config generators.
Lots of answer, but I figured I'd do a summary to properly group them and explain the differences.
First of all, you can define that prefix one of two ways: during configuration time, or when installing, and that's really up to your needs.
During configuration time
Two options:
cmake -S $src_dir -B $build_dir -D CMAKE_INSTALL_PREFIX=$install_dir
cmake -S $src_dir -B $build_dir --install-prefix=$install_dir # Since CMake 3.21
During install time
Advantage: no need to reconfigure if you want to change it.
Two options:
cmake DESTDIR=$install_dir --build $build_dir --target=install # Makefile only
cmake --install $build_dir --prefix=$install_dir