link issue for libc stubs

[Riccardo Manfrin <riccardomanfrin@gmail.com>]

Hi list,
I use gcc 4.8.1 + newlib on a cortex-m3. I'm trying to link my app with 
libc and a library "libtlc.a" that I created out of a bunch of object 
files (init.o, tlc.o, cpu.o) as follows:

arm-none-eabi-ar rcs build/libtlc.a build/core_cm3.o build/cpu.o 
build/startup.o build/init.o build/tlc.o

Within tlc.o I have  the stubs implementation for _exit _sbrk ...
I can see the assembly with objdump ether in the .o and in the libtlc.a 
library.

I try linking with this command

arm-none-eabi-g++  -W -Wall -mcpu=cortex-m3 -mthumb -march=armv7-m 
-nostartfiles  -Wl,-Map=maketest.map  -Wl,-Tlinkerscript.ld main.o -lc 
-lstdc++ -lgcc -ltlc -o maketest.elf

but fail with these errors

... abort.c:63: undefined reference to `_exit' (same error for _sbrk, 
_getpid and _kill).

On the contrary, if I use the object file "tlc.o" in the linking phase, 
I'm able to produce the elf app:

arm-none-eabi-g++  -W -Wall -mcpu=cortex-m3 -mthumb -march=armv7-m 
-nostartfiles  -Wl,-Map=maketest.map  -Wl,-Tlinkerscript.ld main.o 
tlc.o  -lc -lstdc++ -lgcc -ltlc -o maketest.elf

What is the difference? The functions defs are in either tlc.o as well 
as in libtlc.o, but I'm able to produce the binary app only with the 
object file, not with the library.

Thanks,
RM