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For some internal tests, I would like the install prefix to default to a subdirectory of the build directory, unless explicitly overridden by the user. I know the user can specify a install prefix by:
$ cmake -DCMAKE_INSTALL_PREFIX=/foo/bar .. But if the user does not specify this, it should default to, e.g. ${PWD}/installed.
The variable CMAKE_INSTALL_PREFIX is already set to /usr/local, so I cannot just check to see if it unset/empty before setting it.
My current solution is to add a custom switch that the user has to invoke to specify that the CMAKE_INSTALL_PREFIX variable gets respected:
option(ENABLE_INSTALL_PREFIX "Install build targets to system (path given by '-DCMAKE_INSTALL_PREFIX' or '${CMAKE_INSTALL_PREFIX}' if not specified)." OFF) if ( ENABLE_INSTALL_PREFIX ) set (CMAKE_INSTALL_PREFIX installed CACHE PATH "Installation root") else() set (CMAKE_INSTALL_PREFIX installed CACHE PATH "Installation root" FORCE) endif() My questions are:
(a) Are there any issues with the above, beyond the annoyance of the extra flag needing to be passed to CMake to get CMAKE_INSTALL_PREFIX to have an effect?
(b) Is there a better, cleaner, more robust, more idiomatic and/or less annoying way to achieve the above?
Thanks.
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The prefix path is a list of paths. Use this: Also you don't have to point directly into the config file path, you also can point into the directory containing the lib/cmake/... Show activity on this post.
The prefix path is a list of paths. Use this: list (APPEND CMAKE_PREFIX_PATH "/home/rip/Qt/5.12.1/gcc_64") Also you don't have to point directly into the config file path, you also can point into the directory containing the lib/cmake/... Share.
There are two ways to use this variable: passing it as a command line argument just like Job mentioned: cmake -DCMAKE_INSTALL_PREFIX=< install_path > .. assigning value to it in CMakeLists.txt: SET(CMAKE_INSTALL_PREFIX < install_path >) But do remember to place it BEFOREPROJECT(< project_name>)command, otherwise it will not work!
The CMAKE_PREFIX_PATH is set, but everything that's on it is ignored. I found out that you can access the environment variable, split that into a list and append to that to actually append to the prefix path instead of replacing it.
CMake sets the boolean variable CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT if CMAKE_INSTALL_PREFIX has not been explicitly specified and is initialized to its default setting. You can override it in the following way:
if (CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT) set (CMAKE_INSTALL_PREFIX "${CMAKE_BINARY_DIR}/installed" CACHE PATH "default install path" FORCE) endif() A few years ago, I wanted to attempt the same thing. Unfortunately I could never find a fully satisfactory solution. Instead, I chose to use a regex to check if CMAKE_INSTALL_PREFIX matches the default.
E.g. on windows I use the following to create the install dir in the build-directory:
if ( CMAKE_INSTALL_PREFIX MATCHES "^C:/Program Files" ) # Override to an "Install" directory in the current build-dir message( STATUS " Install-prefix was at default -> forcing it to the build-dir" ) message( STATUS " 'set( CMAKE_INSTALL_PREFIX ${CMAKE_CURRENT_BINARY_DIR}/install )'" ) set( CMAKE_INSTALL_PREFIX ${CMAKE_CURRENT_BINARY_DIR}/install ) endif ( CMAKE_INSTALL_PREFIX MATCHES "^C:/Program Files" ) The biggest problem with this construct is that you can specify manually that CMake should install into C:\Program Files. As I distribute my tool with an NSIS-installer this is not an issue (for me).
Perhaps you could try something similar on Unix.
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