exit.c:(.text+0x18): undefined reference to `_exit' when using arm-none-eabi-gcc

Question

I'm new to the field of microcontrollers. I need to port an IDE which is compiling programs for AVR microcontrollers to compile programs for ARM microcontrollers. I have just replaced the compiler from AVR to ARM and added some options as told by someone. The following is the command:

\ARM-GCC\bin\arm-none-eabi-gcc -O0 -ffunction-sections -Wall -std=gnu99 -mfloat-abi=soft 
-Wa,-adhlns="[email protected]" -fmessage-length=0 -mcpu=cortex-m0 -mthumb -g3 -gdwarf-2 -Wl,
--gc-sections -o <Dir_name>\Build_Files\Blink_arm.cpp.elf  <Dir_name>\Build_Files\Blink_arm.cpp.o <Dir_name>\Build_Files\core.a 
-L<Dir_name>\Build_Files -lm

When I execute it I get the follwing error:

tools/arm-gcc/bin/../lib/gcc/arm-none-eabi/4.6.2\libc.a(lib_a-exit.o): In function `exit':
exit.c:(.text+0x18): undefined reference to `_exit'  
collect2: ld returned 1 exit status

May I get some help on what is this error and how can I solve it. And also I don't know what those options in the command line specify.

in your ARM libc (that is bundled with your compiler), the exit() function makes a call to _exit(), which isn't defined in any library. your compiler must be set up incorrectly, although you could perform a quick fix by defining void _exit(int status) yourself (NOTE: this won't work is your libc declares _exit() with a different signature. your _exit() could simply halt in an infinite loop like its AVR counterpart. fixing your GCC installation would be the recommendable option. — Dylan
See: newlib syscalls; you need to implement these, if they are not implemented for your board. Also, there can be issues with your code. Newlib doesn't support everything; See Gatliff's newlib overview. — artless noise

Yercalamarino Yercalamarino · Accepted Answer · 2014-05-28T21:31:03

This happens when compiling a file with arm-none-eabi-gcc in one machine/architecture to load it in an ARM target machine. Most probably you are not making use of semihosting, you want to retarget.

ARM® Compiler toolchain Version 4.1 indicates:

Semihosting is a mechanism that enables code running on an ARM target to communicate and use the Input/Output facilities on a host computer that is running a debugger.

From the toolchain's readme.txt (under folder .../gcc-arm-none-eabi-VERSION/share/doc/gcc-arm-none-eabi):

** non-semihosting/retarget

If you are using retarget, linking like: $ arm-none-eabi-gcc --specs=nosys.specs $(OTHER_LINK_OPTIONS)

For me --specs=nosys.specs was enough ;)

exit.c:(.text+0x18): undefined reference to `_exit' when using arm-none-eabi-gcc

3 Answers