Cross-compiler

A cross compiler is a compiler capable of creating executable code for a platform other than the one on which the compiler is running. For example, a compiler that runs on a Windows 7 PC but generates code that runs on Android smartphone is a cross compiler.

A cross compiler is necessary to compile for multiple platforms from one machine. A platform could be infeasible for a compiler to run on, such as for the microcontroller of an embedded system because those systems contain no operating system. In paravirtualization one machine runs many operating systems, and a cross compiler could generate an executable for each of them from one main source.

Cross compilers are not to be confused with source-to-source compilers. A cross compiler is for cross-platform software development of binary code, while a source-to-source compiler translates from one programming language to another in text code. Both are programming tools.

The fundamental use of a cross compiler is to separate the build environment from target environment. This is useful in a number of situations:

Use of virtual machines (such as Java's JVM) resolves some of the reasons for which cross compilers were developed. The virtual machine paradigm allows the same compiler output to be used across multiple target systems, although this is not always ideal because virtual machines are often slower and the compiled program can only be run on computers with that virtual machine.

Typically the hardware architecture differs (e.g. compiling a program destined for the MIPS architecture on an x86 computer) but cross-compilation is also applicable when only the operating system environment differs, as when compiling a FreeBSD program under Linux, or even just the system library, as when compiling programs with uClibc on a glibc host.

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