Debian Hello World

DART-MX8M-MINI Hello World Using Debian

Build a sample C "Hello, world!" program (Cross Compiling)

Create a file called myhello.c with the following content:

#include <stdio.h>

int main() {
	printf("Hello, World!\n");
	return 0;
}

Export the C (cross-)compiler path:

$ export CC=~/var_mx8mm_dart_debian_buster/toolchain/gcc-linaro-6.3.1-2017.05-x86_64_aarch64-linux-gnu/bin/aarch64-linux-gnu-gcc

Compile:

$ $CC myhello.c -o myhello

Now you should have an app called myhello, that can be run on your target board.
You can add it to your rootfs image or copy it directly to the rootfs on the board (using scp, for example).

Build a sample C "Hello, world!" program on Target

One of the biggest advantages of having Debian OS is you can compile your code directly on the target. Although not recommended as linking big programs can take entire memory but for smaller test is sufficient. This reduces back and forth transfer of the compiled binary between host PC. On Target:

Getting Ready target to install tools

# apt-get install -y gcc g++ automaker cmake build-essential vim

Create myhello.c file via vim

# vim myhello.c

Paste below code,

#include <stdio.h>

int main() {
	printf("Hello, World!\n");
	return 0;
}

ESC :wq! and save the file,

Compile code on Target

# apt-get update; apt-get install build-essentials gcc g++
# gcc myhello.c -o myhello.out

Execute on Target

# ./myhello.out
Hello, World!
#

Compile code via chroot (On PC for target)

$ export ROOTFS_BASE=~/var_mx8mm_dart_debian_buster/rootfs/
$ sudo cp variscite/qemu_64bit/qemu-aarch64-static ${ROOTFS_BASE}/usr/bin/qemu-aarch64-static
$ sudo mount -o bind /proc ${ROOTFS_BASE}/proc
$ sudo mount -o bind /dev ${ROOTFS_BASE}/dev
$ sudo mount -o bind /sys ${ROOTFS_BASE}/sys
$ sudo mount -o bind /dev/pts ${ROOTFS_BASE}/dev/pts
$ sudo chroot $ROOTFS_BASE
# gcc myhello.c -o myhello.out

You have two choices to execute this code on target

• Transfer the binary to target via SCP
• Pack rootfs and re-flash the rootfs.
  

It should have the binary you just compiled.

Clean up after compilation

To unmount the virtual filesystem run the following commands in the same exact order.

$ sudo umount -o bind /dev/pts ${ROOTFS_BASE}/dev/pts
$ sudo umount -o bind /proc ${ROOTFS_BASE}/proc
$ sudo umount -o bind /dev ${ROOTFS_BASE}/dev
$ sudo umount -o bind /sys ${ROOTFS_BASE}/sys

Note: Failing to follow the above order may result in an un-responsive PC.