Save the following as CMakeLists.txtĬmake_minimum_required(VERSION 3.8) project(TestingGenerators) message(STATUS "This message can be seen during generation") add_custom_target(print $ -E echo $ $) Let us take an example to make this clear.
CMAKE GENERATOR GENERATOR
This basically means if generator expression abc evaluates to true, then the value of the generator expression is xyz, otherwise it is an empty string. So, if you see something along the lines: Truth be told, I am not a big fan of generator expressions myself and I believe readability should always win over terseness. Generator expressions are – when used in a CMakeLists.txt file or elsewhere – something that stands out and hinders our understanding with our limited knowledge of CMake language. Of course, mere mortals like you or me do not need to understand the CMake language to work with CMake. The expression b + c will be evaluated and its value will be assigned to the variable a.ĬMake has a language to write CMakeLists.txt (and also to write scripts and modules). This is an assignment statement that involves an expression b + c on the right-hand side of the assignment. For example, consider the following C++ line involving three variables a, b and c: In the world of compilers an expression is something that needs to be evaluated. Visual Studio (from version 6 to the latest version 16).Whereas when a developer is trying to debug a program using an integrated development environment, he would appreciate how easy is it to get from a set of source files and the CMakeLists.txt file, his familiar development environment. In an automated nightly build setup where human intervention is minimal, command line build tool generators are the obvious choice. (If you want to further reduce compilation time, you can check out the incredibuild solution – we are not limited to one system, the build is concurrently distributed across idle CPUs in your local network or even the cloud thereby making the build incredibly fast). This makes it easy to understand what failed during a parallel compilation. Ninja makes sure that the command output is always buffered. Since Ninja is a modern tool, the assumption here is multi-core CPUs which can all be used during a build thereby improving throughput. In Ninja, builds are always run in parallel whereas make depends on flags supported by the underlying compiler to achieve this. The unique selling proposition of Ninja over make is the support for parallel builds. For NMake, which is the make tool bundled with Microsoft Visual Studio, the compiler used will be the Microsoft C++ compiler named cl.Īlthough make has been in existence for a long time now, the complexities of maintaining Makefiles led to the development of other build systems – one of the most successful being Ninja. For example, in Borland Makefile the compiler used for compiling a C++ file is called bcc32. The tools that are used in the actual compilation are different for each of these different Makefiles. Some of the non-standard ones supported by CMake are: There are non-standard Makefiles supported by other programs targeting other platforms.
![cmake generator cmake generator](https://www.incredibuild.com/wp-content/uploads/2021/02/CMake-generator-3.jpg)
Here’s a deep dive on how CMake won over Make. Make is a well-known Unix utility and Makefiles are its input.
![cmake generator cmake generator](https://cmake.org/cmake/help/latest/_images/GUI-Choose-Generator.png)
CMake is invoked from a command line whose environment is already configured for the chosen compiler and build tool. These are generators that support command line build tools. Types of Generatorsīroadly there are two different kinds of CMake Generators. Exactly one CMake Generator is involved in the creation of a build output during the Generate step. A CMake Generator is responsible for creating this input for the native build tool. These build tools expect their input to be in a particular form, for example, a Makefile. What is a CMake Generator? As can be seen from the above diagram, native build tools are responsible for the actual compilation of source files. But what does the generate step do? Read on.
![cmake generator cmake generator](https://i.ytimg.com/vi/7M9_9mQxzcU/maxresdefault.jpg)
While working with CMake command line the generate command internally handles configure step. The configure step in the above diagram is only relevant in GUI builds. But before everything, a refresher on CMake build process is handy: This blog post is entirely about what CMake generators are, why CMake supports so many of them, and when will you need each of them in your development. If you search “CMake” you will definitely come across this sentence: “CMake is not a build system but rather it is a build system generator”. A lot has been said about CMake as undoubtedly CMake is a great tool.