curl/docs/INSTALL-CMAKE.md

Building with CMake

This document describes how to configure, build and install curl and libcurl from source code using the CMake build tool. To build with CMake, you of course first have to install CMake. The minimum required version of CMake is specified in the file CMakeLists.txt found in the top of the curl source tree. Once the correct version of CMake is installed you can follow the instructions below for the platform you are building on.

CMake builds can be configured either from the command line, or from one of CMake's GUIs.

Current flaws in the curl CMake build

Missing features in the CMake build:

• Builds libcurl without large file support
• Does not support all SSL libraries (only OpenSSL, Schannel, Secure Transport, and mbedTLS, wolfSSL)
• Does not allow different resolver backends (no c-ares build support)
• No RTMP support built
• Does not allow build curl and libcurl debug enabled
• Does not allow a custom CA bundle path
• Does not allow you to disable specific protocols from the build
• Does not find or use krb4 or GSS
• Rebuilds test files too eagerly, but still cannot run the tests
• Does not detect the correct strerror_r flavor when cross-compiling (issue #1123)

Configuring

A CMake configuration of curl is similar to the autotools build of curl. It consists of the following steps after you have unpacked the source.

Using cmake

You can configure for in source tree builds or for a build tree that is apart from the source tree.

• Build in the source tree.

  $ cmake -B .

• Build in a separate directory (parallel to the curl source tree in this example). The build directory is created for you.

  $ cmake -B ../curl-build

Fallback for CMake before version 3.13

CMake before version 3.13 does not support the -B option. In that case, you must create the build directory yourself, cd to it and run cmake from there:

$ mkdir ../curl-build
$ cd ../curl-build
$ cmake ../curl

If you want to build in the source tree, it is enough to do this:

$ cmake .

Build system generator selection

You can override CMake's default by using -G <generator-name>. For example on Windows with multiple build systems if you have MinGW-w64 then you could use -G "MinGW Makefiles". List of generator names.

Using ccmake

CMake comes with a curses based interface called ccmake. To run ccmake on a curl use the instructions for the command line cmake, but substitute ccmake for cmake.

This brings up a curses interface with instructions on the bottom of the screen. You can press the "c" key to configure the project, and the "g" key to generate the project. After the project is generated, you can run make.

Using cmake-gui

CMake also comes with a Qt based GUI called cmake-gui. To configure with cmake-gui, you run cmake-gui and follow these steps:

1. Fill in the "Where is the source code" combo box with the path to the curl source tree.
2. Fill in the "Where to build the binaries" combo box with the path to the directory for your build tree, ideally this should not be the same as the source tree, but a parallel directory called curl-build or something similar.
3. Once the source and binary directories are specified, press the "Configure" button.
4. Select the native build tool that you want to use.
5. At this point you can change any of the options presented in the GUI. Once you have selected all the options you want, click the "Generate" button.

Building

Build (you have to specify the build directory).

$ cmake --build ../curl-build

Static builds

The CMake build setup is primarily done to work with shared/dynamic third party dependencies. When linking with shared libraries, the dependency "chain" is handled automatically by the library loader - on all modern systems.

If you instead link with a static library, you need to provide all the dependency libraries already at the link command line.

Figuring out all the dependency libraries for a given library is hard, as it might involve figuring out the dependencies of the dependencies and they vary between platforms and can change between versions.

When using static dependencies, the build scripts mostly assume that you, the user, provide all the necessary additional dependency libraries as additional arguments in the build.

Building statically is not for the faint of heart.

Fallback for CMake before version 3.13

CMake before version 3.13 does not support the --build option. In that case, you have to cd to the build directory and use the building tool that corresponds to the build files that CMake generated for you. This example assumes that CMake generates Makefile:

$ cd ../curl-build
$ make

Testing

(The test suite does not yet work with the cmake build)

Installing

Install to default location (you have to specify the build directory).

$ cmake --install ../curl-build

Fallback for CMake before version 3.15

CMake before version 3.15 does not support the --install option. In that case, you have to cd to the build directory and use the building tool that corresponds to the build files that CMake generated for you. This example assumes that CMake generates Makefile:

$ cd ../curl-build
$ make install