CMake is a cross-platform, open-source tool for defining build processes that run on multiple platforms. In diesem Artikel wird davon ausgegangen, dass Sie mit CMake vertraut sind. This article assumes you're familiar with CMake. CMake wurde in den letzten Releases immer mehr in Visual Studio integriert. CMake has become more and more integrated with Visual Studio over the past few releases.
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Go read it now. CMake is code. Therefore, it should be clean. Use the same principles for CMakeLists. For example, a project might use a common set of compiler warnings. Defining such properties globally in the top-level CMakeLists. Defining such project properties globally makes it easier to manage the project with all its targets.
Those commands operate on the directory level. All targets defined on that level inherit those properties. This increases the chance of hidden dependencies.
Better operate on the targets directly. Different compilers use different command-line parameter formats. Starting with CMake 3. CMake provides a collection of find modules for third-party libraries. For example, Boost doesn't support CMake. Keep in mind to export the right information.
Keep things simple. Don't introduce unnecessary custom variables. CMake is a build system generator, not a build system. It evaluates the GLOB expression to a list of files when generating the build system. The build system then operates on this list of files. Therefore, the build system cannot detect that something changed in the file system.
CMake cannot just forward the GLOB expression to the build system, so that the expression is evaluated when building. CMake wants to be the common denominator of the supported build systems. Not all build systems support this, so CMake cannot support it neither. By defining properties i. The developer does not need to understand the whole system in order to reason about a single target.
The build system handles transitivity. If a target needs properties internally i. But be careful not to declare compile options that affect the ABI. Declare those options globally. This propagates usage requirements from the dependent target to the depending target.
The command also resolves transitive dependencies. Using different compile options for multiple targets may affect ABI compatibility. Packages defined in the same CMake tree are directly accessible. Create a variable that lists all sub-projects. In addition to directory-based scope, CMake functions have their own scope. This means variables set inside functions are not visible in the parent scope.
This is not true of macros. This means variables set in macros will be visible in the calling scope. Arguments to macros are not set as variables, instead dereferences to the parameters are resolved across the macro before executing it.
This can result in unexpected behavior when using unreferenced variables. Generally speaking this issue is uncommon because it requires using non-dereferenced variables with names that overlap in the parent scope, but it is important to be aware of because it can lead to subtle bugs. Those macros are evil. If used on the top level, all targets can use the properties defined by them.
For example, all targets can use i. If a target does not require linking e. It is easy to accidentally create hidden dependencies through other targets with those macros. Create a single toolchain file per platform. To treat warnings as errors, never pass -Werror to the compiler. If you do, the compiler treats warnings as errors.
You can no longer treat warnings as errors, because you no longer get any warnings. All you get is errors. The diagnostics output of those tools will appear in the build output as well as in the IDE. Most of the analysis tools report diagnostics for the current source file plus the associated header. Header files with no associated source file will not be analyzed.
You may be able to set a custom header filter, but then the headers may be analyzed multiple times. Report it as a bug to third-party library authors if a library does not support clients to use CMake.
No clear side-by-side examples of a project using "old school CMake" vs the same project using "Modern CMake".
I do not have 29 hours a day consacred to chasing "Modern CMake" scattered infos. CMake docs? There is no such guide. What about linker flags, then? I added that to the text. I have two. Currently my CMakeList. With this I was successfully able to compile, but during run time application crashes in std::list destructor. I suspect is it is because of incompatibility within these libraries. That is per-target. What about setting linker flags globally? Example use case: recompile all incl.
To all CMake users, quick question here from a newbie. Because I rewrite a lib to cmake. Any new here? Although being a newbie myself I can't recommend you an alternative sorry. The site also has various blog articles for smaller, bite-sized discussions about how to do things mostly CMake-focused. Disclosure: I'm the author of those and also a CMake co-maintainer. Another book recently published is CMake Cookbook. It's a different style to the above, so may appeal to a different audience.
No affiliation with me, just sharing the link. I would suggest to take a look at the usage of "dependent" and "depending" as the way they're used might be confusing for the non native american reader and computer science literate.
A child is a dependent of his parents and a child is also financially depending on his parents. In the example moduleB includes moduleA, it depends on moduleA. IMO, the paragraph quoted below is hard to understand:. I don't get the all recommendations of "Using a library defined in the same CMake tree should look the same as using an external library.
Great post about modern CMake! I'm having a bit of trouble understanding the following rules, they look contradicting to me:. This forces the developers to remember to link against the "global options target" every time they create a new target.
It would be better that this is enforced automatically. Toolchain files set variables, but the modern cmake ask to don't use variables and use properties on targets.
There's a way to get toolchain definitions using properties of some target? It's said not to use GLOB but no alternative is presented. The alternative I know is manually adding every single file to CMakeLists and then re-running cmake, which is one extra step from just re-running cmake when you have a GLOB.
How would one go about doing it the proper way? CMake is a build system generator, not a build system itself and not all actual build systems support it.
Also, it is not very safe and may cause some performance issues because you can not easily determine whethere a GLOB is out of date. Can someone give a practical example of it causing problems? I still feel like avoid GLOB achieves nothing.
The build process is still the same when a new file is added: Rerun CMake then build.
Introduction to CMake by Example
Thank you very much. This was very useful. That was fantastic. Absolutely perfect for getting me started with cmake on hierarchical projects that use shared libraries. Thank you!! Give this man a cookie The best write up on cmake.
Einführung in das Buildsystem Cmake