Question

I have linkers errors(undefined reference) that I cannot solve by myself. I use GCC Sourcery G++ Lite 4.5.2 for ARM.

I have a lot of undefined reference and they almost all refer to assembly file. Here one example :

I have “_CPU_MmuConfigGet” defined in an assembly file named cpu.sx :

.global _CPU_MmuConfigGet
CPU_MmuConfigGet: 
mrc p15,0,r0,c1,c0,0        
mov pc,lr

In a c file named mmu.c , CPU_MmuConfigGet is called :

#include "cpu.h"
U32 MMU_ConfigGet(void) {
    return CPU_MmuConfigGet();
}

Finally, in the header file cpu.h, CPU_MmuConfigGet is declared :

extern U32 CPU_MmuConfigGet(void);

Theses tree files are located in the following folders :

Base/Common/src/mmu.c     
Base/Common/inc/cpu.h     
Base/Common/src/cpu.sx    

From different post I red on the net, I found that I should add an underline to CPU_MmuConfigGet (tried, but didn’t solve my problem). I also red in some forum that , when linking, object file order are important, but in others forums, object order are not important (I’m confused here…). I tried the -S parameter to see the assembly version of mmu.c, but that didn’t help me finding a clue about my error…

Here’s is the compiler command used (I have added -H in case this help finding what is wrong…) :

arm-none-eabi-gcc -c -g3 -gdwarf-2  -H -o"mmu.o" -Wall -Wa,-adhlns="mmu.o.lst" 
-fmessage-length=0 -MMD -MP -MF"mmu.d" -MT"mmu.d" -fpic  -march=armv4t -mcpu=arm7tdmi -mlittle-endian 
-I"../../OS/ngos/hw/cdb89712" -I"../../OS/ngos" -I"../../OS/ngos/include" -I"../../OS/ngos/rtos/ucosii"  
-I"C:/Program Files/CodeSourcery/Sourcery G++ Lite/lib/gcc/arm-none-eabi/4.5.2/include" -I"./"  
-I"src/" -I"../../Common/inc" -I"../../OS/uCOS-II/SOURCE" -I"../../OS/ngos/drivers/arm" 
-I"../../OS/ngos/include/ngos" -I"../../OS/ngip/include" -I"../../OS/ngip/include/ngip" 
-I"../../Dvcscomponent/Inc" -I"../../Inc"  "../../Common/src/mmu.c"
. ../../Common/inc/base.h
. ../../Common/inc/hw7312.h
. ../../Common/inc/serial.h
.. ../../Common/inc/base.h
.. ../../Common/inc/hw7312.h
. ../../Common/inc/base.h
. ../../Common/inc/cpu.h
.. ../../Common/inc/base.h
.. ../../Common/inc/hw7312.h
. ../../Common/inc/mmu.h

Now the assembly command :

arm-none-eabi-gcc -g3 -gdwarf-2  -x assembler-with-cpp -Wa,-adhlns="cpu.o.lst" -Wall -c 
-fmessage-length=0 -MMD -MP -MF"cpu.d" -MT"cpu.d" -fpic -o"cpu.o" -march=armv4t  -mcpu=arm7tdmi -mlittle-endian 
-I"../../OS/ngos/hw/cdb89712" -I"../../Common" -I"../../OS/ngos/drivers/arm" 
"../../Common/src/cpu.sx"

Finally the linking command with the error :

arm-none-eabi-gcc -fpic -mcpu=arm7tdmi -T".\linker.ld" -Wl,-Map,BootLoad.map -g3 -gdwarf-2  -o "BootLoad.elf"  
InitMain.o tsk_main.o ecp.o memalloc.o tsk_ecp.o firmdesc.o crc.o flash.o eth.o firmflash.o 
firmdest.o bcfg.o bootdownload.o cinit.o serial.o cpu.o mmu.o  ngucos.o cdbini.o cs712sio.o  
cs712eth.o  ../../OS/ngos/lib/rtstub/arm/gcc/libngosd4m32l.a ../../OS/ngip/lib/rtstub/arm/gcc/libngipd4m32l.a 
mmu.o: In function `MMU_ConfigGet':
C:\Working\SF2100-0074-BootLoaderMezz\Base\NexGen\BootLoader/../../Common/src/mmu.c:28: undefined reference to `CPU_MmuConfigGet'

I someone have any suggestions, I would be pleased to hear them!

Thanks in advance!

Answer 1

Finally, after consulting the listing of cpu.sx, I was surprised that a part of the file was “missing”. I realized that the file had an include of another assembly file. This included assembly file was ended… by a

.end

directive.

I removed this directive and the project compiled.