How to build a new gcc (optional)

Why this may be needed

RTEMS needs a modern gcc (GNU C-Compiler) toolchain on your host. If you cannot install a compatible version of gcc, you can build it locally.

Note: the documentation was taken from these sites:

https://gcc.gnu.org/wiki/InstallingGCC
https://gcc.gnu.org/install/configure.html

How to build

You first have to review or change some configuration variables in file CONFIG.COMMON.

Activate gcc usage by setting RTEMS_CROSS_USE_LOCAL_GCC to “yes” (see common configuration variables).

gcc directory settings

Note

You usually don’t need to change these.

The installation base directory is given on the command line and gcc will be installed in directory “gcc” below this.

If you want to fine-tune installation, build and source directories, you can do this by changing the following variables in file CONFIG.COMMON:

Note

$INSTALLTOP is defined by bin/setup.sh, $TOP is the directory where rtems-from-scratch is located

Variable	default value	explanation
GCC_INSTALL_DIR	$INSTALLTOP/gcc	Directory where the gnu-c compiler is installed
GCC_SRC_DIR	$TOP/src/gcc	Directory where the gnu-c compiler sources are put
GCC_BUILD_DIR	$TOP/src/gcc/build	Directory where the gnu-c compiler is built
GCC_VERSION	9.3.0	Version of the host gnu-c compiler if this is built locally
GCC_DOWNLOAD_PREREQUISITES	yes	Automatically download prerequisites needed for gcc build
GCC_LANGUAGES	“c,c++”	gcc languages that will be supported
GCC_MAKE_OPTS	“-s -j”	Make options for GCC, remove “-j” if you have low memory

Run the build script

The gcc compiler will be installed in directory GCC_INSTALL_DIR.

Run:

bin/build-gcc.sh

How to use the compiler

In file CONFIG.COMMON variable RTEMS_CROSS_USE_LOCAL_GCC must be set to “yes”.

The compiler is then found by build-crosstools.sh automatically.

If you want to use the compiler other applications, source file setenv.sh which is placed in directory $GCC_INSTALL_DIR as it is defined in file CONFIG.COMMON.

If for example, you defined INSTALLTOP <setup> as ‘/usr/local/rtems’ and didn’t change GCC_INSTALL_DIR in file CONFIG.COMMON the command would be:

. /usr/local/rtems/gcc/setenv.sh

This redefines the PATH variable so the gcc compiler and all it’s tools are found before your system’s gcc compiler and tools.