how to install a cross compiler for core-3399-JD4 board?

Negro旋

Hello, you need to follow this wiki to install Linux-SDK in your PC.
http://wiki.t-firefly.com/en/Core-3399-JD4/Linux.html#compile-ubuntu-firmware-gpt

Negro旋

OK. If you want to run the executable in your PC, you can execute "gcc hello.c -o hello" to get the executable.
If you want to run the executable in your board. There is cross compiler in Linux-SDK. "linux-sdk/prebuilts/gcc/linux-x86/aarch64/gcc-linaro-6.3.1-2017.05-x86_64_aarch64-linux-gnu/bin/" for 64 bit. Then your can execute "./aarch64-linux-gnu-gcc hello.c -o hello" to get the executable.

Negro旋

Yes, if you just want to obtain the executable, just install an arm cross compiler is OK.