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