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