# 3. Compiling avr-gcc

The latest versions of GCC (4.2.3 and up) include support for the ATmega328P, as well as the ATmega48P, ATmega88P, and ATmega168P.

### Checking the currently installed version of avr-gcc

Run the following command:

avr-gcc --version

You can test for support by creating an empty file test.c and running avr-gcc -mmcu=atmega328p test.c. If your version of gcc does not support the chip, you will see the following errors:

unknown MCU 'atmega328p' specified
...
test.c:1: error: MCU "atmega328p" supported for assembler only

### Installing prerequisites

Recent versions of GCC (4.3.x) depend on GMP and MPFR, which can be installed from their web pages. Under Ubuntu, you can get these packages by running the following command.

sudo apt-get install libgmp3-dev libmpfr-dev

Other distributions probably provide similar packages.

Get gcc-4.3.3.tar.bz2 or a later version from the GCC FTP site or from a mirror closer to you if possible. We recommend getting the full GCC, which includes the C++ compiler, not just gcc-core.

### Unpack the archive

Run the following command:

tar xjf ~/Desktop/gcc-4.3.3.tar.bz2
cd gcc-4.3.3

### Configure, compile, and install GCC

Note that you need to compile GCC from a separate directory, and that we are specifying that only C and C++ be included. If you want to try compiling FORTRAN, ObjectiveC, or GCJ for the AVR, you’re on your own!

mkdir obj
cd obj
../configure --prefix=/usr/local --target=avr --enable-languages=c,c++ --disable-nls --disable-libssp
make
sudo make install

### Next steps

The latest version of avr-gcc should now be on your path. Next, proceed to Section 2 to install the latest binutils.

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