Compile simple C program to run on OpenWrt

[DrSamJames]

Hi

I've got a hopefully simple question. I've just ran through the "Hello World" example on the Wiki and successfully produced the .ipk which I transferred to my router, installed the package and ran it to produce "Hello, world!". All great!

But my question is, how do I compile the program directly so I can copy just the program and run it?

I believe I've found the correct GCC compiler, in my case I think it is in:

~/openwrt/staging_dir/toolchain-arm_cortex-a9_gcc-8.4.0_musl_eabi/bin

then used the command to build a program from the .c file:

arm-linux-gnueabihf-gcc -c -o helloworld.o ~/openwrt/code/helloworld/helloworld.c
arm-linux-gnueabihf-gcc -o helloworld helloworld.o

but when I copy the resulting helloworld to my router and try running it with:

./helloworld

I get:

-ash: ./helloworld: not found

I've checked and I think I have the correct permission:

-rwxr-xr-x 1 root root 7984 Aug 14 11:47 helloworld

I'm using a Pi for my development environment and a ASUS RT-AC66U B1 for the test environment.

Thanks

Sam

[Mijzelf]

Do a
file helloworld
on your Pi, and also copy /bin/busybox from your router and run file on it. It should give comparable output

[slh]

Work with the buildsystem, cross compiling involves setting a lot of parameters and environment variables (I'd venture that your previous attempt built against your host's libc and not the target libc (musl)).

[VincentR]

If you want the full command that is being run (not just the compiler), you can rebuild using the verbose option.

make -j1 V=s

then in the output, you'll be able to see the full command (compiler, LD_LIBRARY_PATH, etc). If you run that command manually, it will produce the same output as the make does.