Executable file

Native executable

Executable files typically include a runtime system, which implements runtime language features (such as task scheduling, exception handling, calling static constructors and destructors, etc.) and interactions with the operating system, notably passing arguments, environment, and returning an exit status, together with other startup and shutdown features such as releasing resources like file handles. For C, this is done by linking in the crt0 object, which contains the actual entry point and does setup and shutdown by calling the runtime library. Executable files thus may contain significant code beyond that directly generated from the source code. In some cases, it is desirable to omit this, for example for embedded systems. In C, this can be done by omitting the usual runtime, and instead explicitly specifying a linker script, which generates the entry point and handles startup and shutdown, such as calling main to start and returning exit status to the kernel at the end.