yann@2076: File.........: 6 - Toolchain types.txt
yann@2908: Copyright....: (C) 2010 Yann E. MORIN <yann.morin.1998@free.fr>
yann@2076: License......: Creative Commons Attribution Share Alike (CC-by-sa), v2.5
yann@2076: 
yann@2076: 
yann@2076: Toolchain types  /
yann@2076: ________________/
yann@2076: 
yann@2076: 
yann@2076: There are four kinds of toolchains you could encounter.
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yann@2076: First off, you must understand the following: when it comes to compilers there
yann@2076: are up to four machines involved:
yann@2076:   1) the machine configuring the toolchain components: the config machine
yann@2076:   2) the machine building the toolchain components:    the build machine
yann@2076:   3) the machine running the toolchain:                the host machine
yann@2076:   4) the machine the toolchain is generating code for: the target machine
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yann@2076: We can most of the time assume that the config machine and the build machine
yann@2076: are the same. Most of the time, this will be true. The only time it isn't
yann@2076: is if you're using distributed compilation (such as distcc). Let's forget
yann@2076: this for the sake of simplicity.
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yann@2076: So we're left with three machines:
yann@2076:  - build
yann@2076:  - host
yann@2076:  - target
yann@2076: 
yann@2076: Any toolchain will involve those three machines. You can be as pretty sure of
yann@2076: this as "2 and 2 are 4". Here is how they come into play:
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yann@2076: 1) build == host == target
antony@2564:     This is a plain native toolchain, targeting the exact same machine as the
yann@2076:     one it is built on, and running again on this exact same machine. You have
yann@2076:     to build such a toolchain when you want to use an updated component, such
yann@2076:     as a newer gcc for example.
yann@2076:     crosstool-NG calls it "native".
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yann@2076: 2) build == host != target
yann@2076:     This is a classic cross-toolchain, which is expected to be run on the same
yann@2076:     machine it is compiled on, and generate code to run on a second machine,
yann@2076:     the target.
yann@2076:     crosstool-NG calls it "cross".
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yann@2076: 3) build != host == target
yann@2076:     Such a toolchain is also a native toolchain, as it targets the same machine
yann@2076:     as it runs on. But it is build on another machine. You want such a
yann@2076:     toolchain when porting to a new architecture, or if the build machine is
yann@2076:     much faster than the host machine.
yann@2076:     crosstool-NG calls it "cross-native".
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yann@2076: 4) build != host != target
yann@2076:     This one is called a canadian-toolchain (*), and is tricky. The three
yann@2076:     machines in play are different. You might want such a toolchain if you
yann@2076:     have a fast build machine, but the users will use it on another machine,
yann@2076:     and will produce code to run on a third machine.
yann@2076:     crosstool-NG calls it "canadian".
yann@2076: 
yann@2076: crosstool-NG can build all these kinds of toolchains (or is aiming at it,
yann@2076: anyway!)
yann@2076: 
yann@2076: (*) The term Canadian Cross came about because at the time that these issues
yann@2076:     were all being hashed out, Canada had three national political parties.
yann@2076:     http://en.wikipedia.org/wiki/Cross_compiler