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In this tutorial we will create a GCC cross-compiler for your own operating system. This compiler is specially made to target exactly your operating system and is what allows you to leave the current operating system behind. You ''need'' a cross-compiler for operating systems development, unless you are developing on your own operating system.
This tutorial focuses onc reating a GCC cross-compiler for your own operating system. This compiler that we build here will have a generic target (i686-elf) what allows you to leave the current operating system behind, meaning that no headers or libraries of your host operating system will be used. You ''need'' a cross-compiler for operating system development, otherwise a lot of unexpected things can happen because the compiler assumes that your code is running on your host operating system.


== Introduction ==
== Introduction ==


Generally speaking, a cross-compiler is a compiler that runs on platform A (the '''host'''), but generates executables for platform B (the '''target'''). These two platforms may (but do not need to) differ in CPU, operating system, and/or [[:Category:Executable Formats|executable format]]. In our case, the host platform is your current operating system, and the target platform is the operating system you are about to make. It is important to realize that these two platforms are not the same; your operating system is always going to be different from your current operating system. This is why we need to build a cross-compiler first, you will most certainly run into trouble otherwise.
Generally speaking, a cross-compiler is a compiler that runs on platform A (the '''host'''), but generates executables for platform B (the '''target'''). These two platforms may (but do not need to) differ in CPU, operating system, and/or [[:Category:Executable Formats|executable format]]. In our case, the host platform is your current operating system and the target platform is the operating system you are about to make. It is important to realize that these two platforms are not the same; your operating system is always going to be different from your current operating system. This is why we need to build a cross-compiler first, you will most certainly run into trouble otherwise.


=== Why do I need a Cross Compiler? ===
=== Why cross-compilers are necessary ===
{{Main|Why do I need a Cross Compiler?}}
{{Main|Why do I need a Cross Compiler?}}


You need to use a cross-compiler ''unless'' you are developing on your own operating system. The compiler must know the correct target platform (CPU, operating system), otherwise you will run into trouble. If you use the compiler that comes with your system, then the compiler won't know it is compiling something else entirely. Some tutorials suggest using your system compiler and passing a lot of problematic options to the compiler. This will certainly give you a lot of problems in the future and the solution is build a cross-compiler. If you have already attempted to make an operating system without using a cross-compiler, please read the article [[Why do I need a Cross Compiler?]].
You need to use a cross-compiler ''unless'' you are developing on your own operating system. The compiler must know the correct target platform (CPU, operating system), otherwise you will run into trouble. If you use the compiler that comes with your system, then the compiler won't know it is compiling something else entirely. Some tutorials suggest using your system compiler and passing a lot of problematic options to the compiler. This will certainly give you a lot of problems in the future and the solution is build a cross-compiler. If you have already attempted to make an operating system without using a cross-compiler, please read the article [[Why do I need a Cross Compiler?]].


=== Which compiler version do I want? ===
=== Which compiler version to choose ===
{{Main|Building GCC}}
{{Main|Building GCC}}


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You may be able to use an older major GCC release to build a cross-compiler of a newer major GCC release. For instance, GCC 4.7.3 may be able to build a GCC 4.8.0 cross-compiler. However, if you want to use the latest and greatest GCC version for your cross-compiler, we recommend that you [[Building GCC|bootstrap the newest GCC]] as your system compiler first. Individuals using OS X 10.7 or earlier might want to invest in either building a system GCC (that outputs native Mach-O), or upgrading the local LLVM/Clang installation. Users with 10.8 and above should install the Command Line Tools from Apple's developer website and use Clang to cross-compile GCC.
You may be able to use an older major GCC release to build a cross-compiler of a newer major GCC release. For instance, GCC 4.7.3 may be able to build a GCC 4.8.0 cross-compiler. However, if you want to use the latest and greatest GCC version for your cross-compiler, we recommend that you [[Building GCC|bootstrap the newest GCC]] as your system compiler first. Individuals using OS X 10.7 or earlier might want to invest in either building a system GCC (that outputs native Mach-O), or upgrading the local LLVM/Clang installation. Users with 10.8 and above should install the Command Line Tools from Apple's developer website and use Clang to cross-compile GCC.


=== Which Binutils version do I want? ===
=== Which binutils version to choose ===
{{Main|Cross-Compiler Successful Builds}}
{{Main|Cross-Compiler Successful Builds}}
We recommend that you use the latest and greatest [[Binutils]] release. Note, however, that not all combinations of GCC and Binutils work. If you run into trouble, use a Binutils that was released at roughly the same time as your desired compiler version. You probably need at least Binutils 2.22, or preferably the latest 2.23.2 release. It doesn't matter what Binutils version you have installed on your current operating system.
We recommend that you use the latest and greatest [[Binutils]] release. Note, however, that not all combinations of GCC and Binutils work. If you run into trouble, use a Binutils that was released at roughly the same time as your desired compiler version. You probably need at least Binutils 2.22, or preferably the latest 2.23.2 release. It doesn't matter what Binutils version you have installed on your current operating system.
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This will allow the build to proceed. The reason this happens is that the <tt>mingw32</tt> (and mingw itself) configures <tt>INCLUDE_PATH</tt> and <tt>LIBRARY_PATH</tt> to be, as can be guessed, <tt>/mingw/include</tt> and <tt>/mingw/lib</tt>, instead of the defaults <tt>/usr/include</tt> and <tt>/usr/lib</tt>. Why the build fails even though nothing is required in those folders, and why it doesn't just make them, is beyond me.
This will allow the build to proceed. The reason this happens is that the <tt>mingw32</tt> (and mingw itself) configures <tt>INCLUDE_PATH</tt> and <tt>LIBRARY_PATH</tt> to be, as can be guessed, <tt>/mingw/include</tt> and <tt>/mingw/lib</tt>, instead of the defaults <tt>/usr/include</tt> and <tt>/usr/lib</tt>. Why the build fails even though nothing is required in those folders, and why it doesn't just make them, is beyond me.

== More advanced ==
Using this simple cross compiler will be sufficient for quite some time, but at some point you will want the compiler to automatically include your own system headers and libraries. Building an [[OS Specific Toolchain|OS-specific toolchain]] for your own operating system is the way to go from here.


== See Also ==
== See Also ==
Retrieved from "https://osdev.wiki/wiki/GCC_Cross-Compiler"