GNU Arm Embedded Toolchain

link error: undefined reference to '_exit'

Asked by lobachevsky

hi, all,

I am trying to write a program for Cortex-M0 core.

The compile is success, but with link error by using the following flags in makefile

CFLAGS = --specs=rdimon.specs -Wl,--start-group -lgcc -lc -lc -lm -lrdimon -Wl,--end-group -mthumb -mcpu=cortex-m0

However, an error happens:

c:/program files/gnu tools arm embedded/4.7 2013q1/bin/../lib/gcc/arm-none-eabi/exit.c: (.text.exit+0x2c): undefined reference to '_exit'.

I have searched online, and read the readme under C:\Program Files\GNU Tools ARM Embedded\4.7 2013q1\share\doc\gcc-arm-none-eabi. They all said that a C lib is needed for the link, where --specs=rdimon.specs flag can solve the problem. However, without success.

Anyone knows how can I do?

Thanks a lot!

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chengbin (can-finner) said : 		#1

Hi,
What's your linking command line? Could you dump the command line and paste it here?

And two points about linking static library for bare-metal programs:
1. Use arm-none-eabi-gcc, rather than arm-none-eabi-ld to do the job;
2. Always make sure that options like "-lc ..." are after *.c/*.o in command line.

Hoping this can help.

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lobachevsky (nirvanno) said : 		#2

hi, chengbin,

Thanks a lot for your answer.

I tried what you said like below:
$(CC) --specs=rdimon.specs -mthumb -mcpu=cortex-m0 $(OBJECTS) -Wl,--start-group -lgcc -lc -lc -lm -lrdimon -Wl,--end-group

where $(CC) is arm-none-eabi-gcc, and $(OBJECTS) is my object file, which are some *.o.

However, still with the error:
c:/program files/gnu tools arm embedded/4.7 2013q1/bin/../lib/gcc/arm-none-eabi/lib/libc.a(lib_a-exit.o): In function 'exit': exit.c": (.text.exit+0x2c): undefined reference to '_exit'.

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Joey Ye (jinyun-ye) said : 		#3

This is weird. It does work with my examples in hand. It might be a bug in tools or installation problem in a machine.

To verify, I'd suggest to reduce your project to just a hello-world progam with a simple object file, and see what happens.

It will be very helpful for us to address the issue if you can please try it and report the output.

Thanks,
Joey

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lobachevsky (nirvanno) said : 		#4

hi, Joey,

I have re-install my tool chain, and change the command as following:

arm-none-eabi-gcc main.c -mthumb -mcpu=cortex-m0 -Os --specs=nano.specs --specs=rdimon.specs -lc -lc -lrdimon -o main

And it was success.

So it seams something wrong with my installation & command sequence.

Any way, the problem is solved.

Thanks a lot for you advice.