Cross Compiler GCC

• the compiler must know the correct target platform that the programmer is targeting
• the default compiler targets the hosts system by default
• building a cross compiler or downloading an existing cross compiler solves this problem
• cross compiler is needed to support builds for different cpu architectures and operating systems

For this project we are going to build our own GCC Cross Compiler

• os dev has guidelines for building your own cross compiler

  gcc --version
  

• to build a minimal cross compiler gcc and binutils are needed

  ld --version
  

• for detailed guidelines refer: OS DEV CROSS COMPILER GCC

Tools required for the build OS dev

replace dnf with apt for debian/ ubuntu and pacman -S for arch

1. GCC - core compiler

   sudo dnf install gcc
   

2. G++ - required for new gcc versions

   sudo dnf install g++
   

3. MAKE - automate the build system

   sudo dnf install make
   

4. BISON - parser

   sudo dnf install bison
   

5. FLEX - lexical analyzer generator

   sudo dnf install flex
   

6. GMP (math library) - handles large arithmetic

   sudo dnf install gmp-devel
   

7. MPFR(floating point math) - precise floating-point calculations

   sudo dnf install mpfr-devel
   

8. MPC(complex math) - complex number arithmetic

   sudo dnf install libmpc-devel
   

9. TEXINFO - generate GCC documentation

   sudo dnf install texinfo
   

10. ISL (OPTIONAL) - advanced loop optimizations and code analysis

    sudo dnf install isl-devel
    

Steps

1. install the above tools
2. install the gcc and binutils source code from binutils and GCC
3. commands

# defining the path and the target

#defining the path where everything will be installed
export PREFIX="$HOME/opt/cross"

# the target architecture i686 is for 32 bit mode and the file output -elf is for flat binary output file
export TARGET=i686-elf

# adding the compiler to the path
export PATH="$PREFIX/bin:$PATH"

# make sure that the folder names are the below mentioned
# src is the source folder where the extracted source code is saved
cd $HOME/src

# compiling binutils replace x.y.z with the downloaded version
mkdir build-binutils
cd build-binutils

# target is defining the architecture to target
# prefix install location
# with sysroot enables a virtual root file system
# disable nls disables native language support
# disable werror suppresses warnigs being treated as errors
../binutils-x.y.z/configure --target=$TARGET --prefix="$PREFIX" --with-sysroot --disable-nls --disable-werror
make
make install

cd $HOME/src

# compiling gcc replace x.y.z with the downloaded version
mkdir build-gcc
cd build-gcc

# target is defining the architecture to target
# prefix install location
# with sysroot enables a virtual root file system
# disable nls disables native language support
# enable languages is defining the support for the supported languages
# without headers is dont expect any existing standard libraries
# disable werror suppresses warnings being treated as errors
# disable hosted libstdcxx disables hosted c++ standard library features
../gcc-x.y.z/configure --target=$TARGET --prefix="$PREFIX" --disable-nls --enable-languages=c,c++ --without-headers --disable-hosted-libstdcxx
make all-gcc
make all-target-libgcc
make all-target-libstdc++-v3
make install-gcc
make install-target-libgcc
make install-target-libstdc++-v3

## to verify the cross compiler build
$HOME/opt/cross/bin/i686-elf-gcc --version

## to make the cross compile shareable 
tar -czf i686-elf-gcc.tar.gz -C $HOME/opt cross