Compiling basic C file for the ARM processor

Question

I am using the Yagarto recompilation of the GCC toolchain. I am trying to compile this simple program to get an .elf executable:

int main(void)
{
    return(0);
}

When typing the command arm-none-eabi-gcc main.c I get the error message

c:/yagarto/bin/../lib/gcc/arm-none-eabi/4.6.2/../../../../arm-none-eabi/lib\libc.a(lib_a-exit.o): In function exit': C:\msys\1.0\home\yagarto\newlib-build\arm-none-eabi\newlib\libc\stdlib/../../../../../newlib-1.19.0/newlib/libc/stdlib/exit.c:65: undefined reference to_exit' collect2: ld returned 1 exit status

What am I doing wrong?

do you have the ARM standard C library available in your build environment? Because your linker says "no". — tbert
It seems like I haven't. How can I get the ARM standard C library in my build environment? — Randomblue
always most common libraries have been included with the tool chain itself. either you might not properly configure the library path or you may need to explicitly link with the library. — theB

Bart Bart · Accepted Answer · 2012-03-09T12:25:10

Newlib requires you to define an _exit symbol. There might also be other symbols that you have to provide to make newlib work: http://sourceware.org/newlib/libc.html#Stubs

Something like this should be sufficient (assuming you are compiling for a microcontroller, don't do this when you have an OS):

.globl _exit
_exit:
    b     . // Loop until reset

Or in C:

void _exit(void) {
    while(1) {
        // Loop until reset
    }
}

BTW: you might want to disable interrupts before spinning.

EDIT: Maybe a litte bit extra information. Yagarto includes Newlib as libc, which is a library providing functions like printf(), malloc(), etc. However, it cannot know how to send a character to a screen or console (in case of printf), or how to exit in case you call abort() or exit(). Therefore, Newlib requires you to provide implementations of a few basic function, depending on what functionality of Newlib you use.

Compiling basic C file for the ARM processor

2 Answers