findpackage

Find_package is a mechanism used by build systems to locate and configure external libraries or packages so they can be used by a project. It typically determines the presence of a package, discovers its include directories and libraries, and exposes ways to link against it or use its interfaces. This helps projects remain portable across platforms and compiler environments.

In CMake, find_package is a command that searches for a package's configuration either through a package configuration file (Config.cmake) or through a find module (Find<Package>.cmake). There are two common modes: config mode, which relies on a package’s own configuration file, and module mode, which uses a community or project supplied Find module. When a package is located, CMake defines variables such as <Package>_FOUND and can create imported targets like <Package>::<Name>. If the package is not found, the variable is set to FALSE unless the search was marked REQUIRED, in which case an error is produced.

Usage typically involves optional version requirements and component selection. For example, find_package(OpenSSL 1.1 REQUIRED) may expose targets like OpenSSL::SSL and OpenSSL::Crypto for linking, while find_package(Threads REQUIRED) enables usage through built-in imported targets. In modern CMake, it is recommended to link against imported targets rather than raw libraries, for example: target_link_libraries(myapp PRIVATE OpenSSL::SSL OpenSSL::Crypto).

Path and module search behavior depends on variables such as CMAKE_PREFIX_PATH, CMAKE_MODULE_PATH, and hints provided by the project. These controls determine where CMake looks for Config.cmake files or Find modules.