Put simply, a compiler takes source code as input and produces a binary executable as output. Cross compilation refers to the case where the binary code produced is designed to execute on a different machine architecture than the host system.
For example: Using a C compiler on a PPC system to produce code to run on an Intel.
A cross-compilation environment (refered to as the toolchain) provides a number of advantages, even when the host and target architectures are the same.
- Strict control of the version on cc, libc and binutils used
- The build process can be run as a non-root user on the host unix system, preventing damage to the host system if the toolchain misbehaves
- Enviroment variables affecting cross toolchains
- a version of gcc and binutils that supports cross compilation is required in the host enviroment
- headers to link against are required
- libraries are required to be present that are compatible with the target system.