inline functions have "first defined here" and "multiple defenition"

Like two of my previous questions (inline-asm-with-gcc & arm7tdmi-does-not-support-requested-special-purpose-register, I have some build problem when converting code compiled with ARMASM to gcc(code sourcery GCC-4.6.2 eabi).

This time is at linking process: I get a lot of "first defined here" and "multiple definition" to inline functions. Example :

inline U16 ByteSwap16(U16 uData) { return ( (uData >> 8) | (uData << 8) ); } 

I get " multiple definition of `ByteSwap16' " and "first defined here" on the first line.

Here's the linking parameter that I use for the file with the error :

arm-none-eabi-ld -T".\linker.ld" -Map=BootLoad.map -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 nginit.o MmuSdram0.o ../../OS/ngos/lib/rtstub/arm/gcc/libngosd4m32l.a ../../OS/ngip/lib/rtstub/arm/gcc/libngipd4m32l.a 

In case the error comes in compilation process :

arm-none-eabi-gcc -c -H -Wall -Wa,-adhlns="tsk_main.o.lst" -fmessage-length=0 -MMD -MP -MF"tsk_main.d" -MT"tsk_main.d" -fpic -o"tsk_main.o" -march=armv4t -mcpu=arm7tdmi -mlittle-endian -g3 -gdwarf-2 -O0 -I"../../OS/ngos/hw/cdb89712" -I"../../OS/ngos" -I"../../OS/ngos/include" -I"../../OS/ngos/rtos/ucosii" -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" "src/tsk_main.c" 

Any idea why the inline function generate theses errors?

Thanks in advance!