Once in a while I write some documentation... Not often enough...

Yann E. MORIN" 16 years ago
parent afaffaea38
commit 8c5cfe649d

@ -22,9 +22,9 @@ Toolchains are made of different piece of software, each being quite complex
and requiring specially crafted options to build and work seamlessly. This
is usually not that easy, even in the not-so-trivial case of native toolchains.
The work reaches a higher degree of complexity when it comes to cross-
compilation, where it can becomes quite a nightmare...
compilation, where it can become quite a nightmare...
Some cross-toolchain exits on the internet, and can be used for general
Some cross-toolchains exist on the internet, and can be used for general
development, but they have a number of limitations:
- they can be general purpose, in that they are configured for the majority:
no optimisation for your specific target,
@ -100,6 +100,67 @@ toolchain.
You are then free to add the toolchain /bin directory in your PATH to use
it at will.
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 building 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, targetting 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.
ct-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.
ct-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.
ct-ng calls it "cross-native".
4) build != host != target
This one is called a canadian-toolchain (*), is 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.
ct-ng calls it "canadian".
ct-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.
Internals /