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     1.4 +File.........: 6 - Toolchain types.txt
     1.5 +Copyrigth....: (C) 2010 Yann E. MORIN <yann.morin.1998@anciens.enib.fr>
     1.6 +License......: Creative Commons Attribution Share Alike (CC-by-sa), v2.5
     1.7 +
     1.8 +
     1.9 +Toolchain types  /
    1.10 +________________/
    1.11 +
    1.12 +
    1.13 +There are four kinds of toolchains you could encounter.
    1.14 +
    1.15 +First off, you must understand the following: when it comes to compilers there
    1.16 +are up to four machines involved:
    1.17 +  1) the machine configuring the toolchain components: the config machine
    1.18 +  2) the machine building the toolchain components:    the build machine
    1.19 +  3) the machine running the toolchain:                the host machine
    1.20 +  4) the machine the toolchain is generating code for: the target machine
    1.21 +
    1.22 +We can most of the time assume that the config machine and the build machine
    1.23 +are the same. Most of the time, this will be true. The only time it isn't
    1.24 +is if you're using distributed compilation (such as distcc). Let's forget
    1.25 +this for the sake of simplicity.
    1.26 +
    1.27 +So we're left with three machines:
    1.28 + - build
    1.29 + - host
    1.30 + - target
    1.31 +
    1.32 +Any toolchain will involve those three machines. You can be as pretty sure of
    1.33 +this as "2 and 2 are 4". Here is how they come into play:
    1.34 +
    1.35 +1) build == host == target
    1.36 +    This is a plain native toolchain, targetting the exact same machine as the
    1.37 +    one it is built on, and running again on this exact same machine. You have
    1.38 +    to build such a toolchain when you want to use an updated component, such
    1.39 +    as a newer gcc for example.
    1.40 +    crosstool-NG calls it "native".
    1.41 +
    1.42 +2) build == host != target
    1.43 +    This is a classic cross-toolchain, which is expected to be run on the same
    1.44 +    machine it is compiled on, and generate code to run on a second machine,
    1.45 +    the target.
    1.46 +    crosstool-NG calls it "cross".
    1.47 +
    1.48 +3) build != host == target
    1.49 +    Such a toolchain is also a native toolchain, as it targets the same machine
    1.50 +    as it runs on. But it is build on another machine. You want such a
    1.51 +    toolchain when porting to a new architecture, or if the build machine is
    1.52 +    much faster than the host machine.
    1.53 +    crosstool-NG calls it "cross-native".
    1.54 +
    1.55 +4) build != host != target
    1.56 +    This one is called a canadian-toolchain (*), and is tricky. The three
    1.57 +    machines in play are different. You might want such a toolchain if you
    1.58 +    have a fast build machine, but the users will use it on another machine,
    1.59 +    and will produce code to run on a third machine.
    1.60 +    crosstool-NG calls it "canadian".
    1.61 +
    1.62 +crosstool-NG can build all these kinds of toolchains (or is aiming at it,
    1.63 +anyway!)
    1.64 +
    1.65 +(*) The term Canadian Cross came about because at the time that these issues
    1.66 +    were all being hashed out, Canada had three national political parties.
    1.67 +    http://en.wikipedia.org/wiki/Cross_compiler