Is there a simple way to find either the root, or the "installed" subdirectory of Microsoft's Vcpkg, from within a CMake build script? Let's assume the CMAKE_TOOLCHAIN_FILE has already been set to the standard vcpkg.cmake file.
You most likely need to set an environment variable to tell CMake where to find the toolchain file.
Possible answer: Call cmake with -DCMAKE_TOOLCHAIN_FILE=%VCPKG_ROOT%\scripts\buildsystems\vcpkg.cmake
Related
I want to pass an additional parameter to cmake relative to where it is.
My libraries are in:
C:/bla/imgui
C:/bla/imgui-integration
From
C:/bla/imgui-integration/build folder I want to refer to C:/bla/imgui in a parameter named IMGUI_DIR :
cmake .. -DIMGUI_DIR="${CMAKE_CURRENT_SOURCE_DIR}/../imgui"
The problem is that I tried every combination of :
-DIMGUI_DIR="${CMAKE_CURRENT_SOURCE_DIR}/../../imgui"
-DIMGUI_DIR="${CMAKE_CURRENT_SOURCE_DIR}/imgui"
And none of them works.
Only works if I directly use:
-DIMGUI_DIR="C:/bla/imgui"
What am I doing wrong exactly?
As Tsyvarev said in a comment:
CMAKE_CURRENT_SOURCE_DIR is a CMake variable, which is set by CMake
when it interprets your project. But when running cmake <..> you use
shell scripting. You need to use abilities of the shell for prepare
needed parameters
I can't use cmake variables in the shell that will be interpreted inside cmake.
In my CMake package, there is a call to find_package. This succeeds, great! However, it turns out to be the wrong version of the package. I now want to go and delete that package. However, I have no idea where the heck it is on my system, nor where the -config.cmake file is that CMake must have found somewhere. Is there a way to get find_package to give me this information? Or at least verbosely tell me where it is searching?
I though this might be in the variable CMAKE_MODULE_PATH, however that is empty for me. So I guess it is in the default paths somewhere. But CMake searches a lot of places for packages, and I didn't find it in the usual locations that I remember.
Ah ok, I found a solution here:
https://riptutorial.com/cmake/example/21128/debug-find-package---errors
Turns out there is a special debug flag to make find_package tell you where it is searching:
cmake -D CMAKE_FIND_DEBUG_MODE=ON ..
As of CMake 3.17, the cmake command line has native support for printing the search directories for all of the CMake find_* commands. Use the --debug-find flag:
cmake --debug-find ..
Edit: The accepted answer actually shows that it is pretty normally possible to set CMAKE_MODULE_PATH as any other CMake variable e.g. via the -DCMAKE_MODULE_PATH path CLI parameter. It seems that in my case there is some included CMake script that calls set(CMAKE_MODULE_PATH /library_path), which erases all previous paths set to the variable. That's why I couldn't get the variable to do what I wanted it to do. I'll leave the question here in case anybody else faces this kind of situation.
I'm building a (3rd party) project that uses the Protobuf library (but this question is general). My system has a system-wide install of a newer version of Protobuf than the project is compatible with. So I've downloaded and compiled from source an older version of Protobuf.
The project uses CMake, and in its CMakeLists.txt, there is:
find_package(Protobuf REQUIRED)
Which, however, finds the (incompatible) system install. Of course, CMake doesn't know about my custom build of Protobuf. But how do I tell it?
I've created a FindProtobuf.cmake file in, say, ~/usr/share/cmake-3.0/Modules/ and want the build process to use this one for finding Protobuf. But I haven't succeeded forcing CMake to pick up this one and not the system one. I think the reason is quite obvious from the CMake docs of find_package:
The command has two modes by which it searches for packages: “Module” mode and “Config” mode. Module mode is available when the command is invoked with the above reduced signature. CMake searches for a file called Find<package>.cmake in the CMAKE_MODULE_PATH followed by the CMake installation. If the file is found, it is read and processed by CMake. ... If no module is found and the MODULE option is not given the command proceeds to Config mode.
So until I succeed to change CMAKE_MODULE_PATH, CMake will just pick up the FindProtobuf.cmake installed to the default system path and won't ever proceed to the "Config" mode where I could probably make use of CMAKE_PREFIX_PATH.
It's important for me to not edit the CMakeLists.txt since it belongs to a 3rd party project I don't maintain.
What I've tried (all without success):
calling CMAKE_MODULE_PATH=~/usr/share/cmake-3.0/Modules cmake ... (the env. variable is not "transferred" to the CMake variable with the same name)
calling cmake -DCMAKE_MODULE_PATH=~/usr/share/cmake-3.0/Modules ... (doesn't work, probably by design?)
calling Protobuf_DIR=path/to/my/protobuf cmake ... (the project doesn't support this kind of override for Protobuf)
It seems to me that, unfortunately, the only way to alter the CMAKE_MODULE_PATH used by find_package is to alter it from within CMakeLists.txt, which is exactly what I want to avoid.
Do you have any ideas/workarounds on how not to touch the CMakeLists.txt and still convince find_package to find my custom Protobuf?
For reference, the CMake part of this project is on github .
As a direct answer to your question, yes, you can set CMAKE_MODULE_PATH at the command line by running cmake -DCMAKE_MODULE_PATH=/some/path -S /path/to/src -B /path/to/build.
But that probably doesn't do what you want it to do; see below.
The Bitbucket link you supplied is dead, but here are a few suggestions that might help.
Avoid writing your own find modules, especially when the upstream supplies CMake config modules.
You can direct CMake to your custom Protobuf installation by setting one of CMAKE_PREFIX_PATH or Protobuf_ROOT (v3.12+) to the Protobuf install root.
You can tell find_package to try CONFIG mode first by setting CMAKE_FIND_PACKAGE_PREFER_CONFIG to true (v3.15+). Then set Protobuf_DIR to the directory containing ProtobufConfig.cmake.
Failing all else, you can manually set the variables documented in CMake's own FindProtobuf module, here: https://cmake.org/cmake/help/latest/module/FindProtobuf.html
All these variables can be set at the configure command line with the -D flag.
There are very few environment variables that populate CMake variables to start and I would avoid relying on them. There is an exhaustive list here: https://cmake.org/cmake/help/latest/manual/cmake-env-variables.7.html. CMAKE_MODULE_PATH is not among them.
I am porting some code over to windows and my cmake checks for the package Libavahi using
find_package(Libavahi)
I have the headers, dll, etc. but I'm not sure where to place these such that cmake will find them.
Where can I put these files to be found by cmake? They're in a folder called usr.
I see that the module path is specified using:
set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake/Modules/")
but I'm wondering if there is a default location that will be searched as well
The CMake manual fully specifies the rather complicated search order for the different find_* commands. Unfortunately, since Windows lacks a default directory structure à la /usr/local/lib, it is hard to come up with reasonable defaults here.
One of the most reliable ways of managing directories is through environment variable hints. You simply add an $ENV{MY_VAR} to the HINTS section of the find command and then document that environment variable in your project's readme. Most users that are capable of compiling a C++ program know how to use environment variables, and it is way more convenient than having to give the path on the command line every time (although it never hurts to leave that as an additional option).
For find_package CMake offers a special mechanism on Windows called the package registry. CMake maintains a list of package information in the Windows registry under HKEY_CURRENT_USER\Software\Kitware\CMake\Packages\. Packages build from source can register there using the export command. Other projects build later on the same machine will then be able to find that package without additional configuration. This is quite powerful if you need to build a lot of interdependent projects from source on the same machine.
Update: Starting with version 3.12, CMake now implicitly considers the <PackageName>_Root environment variable a HINT for every find_package call.
In the newer versions of cmake, you can use the --debug-find option to list the directories that cmake is searching through. Somethin like:
cmake -DCMAKE_BUILD_TYPE=Release -DBUILD_TOOLS=ON --debug-find .
For external libraries the user can specify a non-standard location by adding the path to the CMAKE_FLAGS or by adding -DMYLIB_ROOT. Within the CMake script I want to find the library's pkg-config pc file. Because the pc file is not in the standard folder, it is not found by pkg-config with FindPkgConfig's pkg_search_module.
I tried to add the user-given path to the PKG_CONFIG_PATH but it seemed to be ignored:
include(FindPkgConfig)
set(PKG_CONFIG_PATH "${PKG_CONFIG_PATH}:${MYLIB_ROOT}/lib/pkgconfig")
pkg_search_module(PKG_MYLIB mylib)
if(${PKG_MYLIB_FOUND})
...
When I call pkg-config from the terminal with the modified PKG_CONFIG_PATH set, it find the pc file. What am I doing wrong? How can I get pkg_search_module working? I'd like to avoid calling pkg-config directly from CMake.
Maybe the following will do the job
set( ENV{PKG_CONFIG_PATH} "$ENV{PKG_CONFIG_PATH}:${MYLIB_ROOT}/lib/pkgconfig" )
This is a known issue and a ticket exists in CMake's bugtracker, but it is backlocked due to lack of developer interest. I guess one has to provide a patch first...
Edit: According to the bugtracker the feature has been implemented and is part of CMake 3.1.