Creating a "system" static lib

Question

Hi, 
 
 I'm working on a project where I need for some reason to create a "system" static lib. 
 What I mean by "system" is a lib where all nrf_driver, startup file, etc are grouped in a single .a file. 
 This will be later used by arm-none-eabi-gcc to compile a single main.c file and linked with the static lib. 
 To test this I used the 'uart' example : 
 cd $(UART_EXAMPLE_ARMGCC)
make VERBOSE=1
mv _build/nrf52840_xxaa/main.c.o .. // So that main.c.o is not integrated in the static lib
arm-none-eabi-ar rcs _build/libnrf52.a _build/nrf52840_xxaa/*.o
arm-none-eabi-gcc -O3 -g3 -mthumb -mabi=aapcs -L ../../../../../../components/toolchain/gcc -Tuart_gcc_nrf52.ld -mcpu=cortex-m4 -mfloat-abi=hard -mfpu=fpv4-sp-d16 -Wl,--gc-sections --specs=nano.specs _build/main.c.o _build/libnrf52.a -o _build/nrf52840_xxaa.out
arm-none-eabi-objcopy -O ihex _build/nrf52840_xxaa.out _build/nrf52840_xxaa.hex
nrfjprog -f NRF52 --program nrf52840_xxaa.hex --chiperase -r

The 'arm-none-eabi-gcc' line is juste the same line prompted when the 'make VERBOSE=1' but i replaced the .in file (listing all objects) by the main.c.o and libnrf52.a 
 
 The problem I have is that there is no output on the uart. 
 
 I tried the same process with the blinky example and it works great. 
 I also tried to replace libnrf52.a with all the .o objects files and it works great. 
 So the problem comes from the library creation step but I don't know what's wrong with it. 
 
 So my question is do you have any idea why it is not working for the uart example ? 
 Any advice would be appreciated :) 
 
 Thanks

Zoptune · Accepted Answer

Ok so I finally succeed to get the output using the static lib I generated. 
 In my last comment I said that all object files in the static lib were not linked. 
 To force gcc to link every file in the lib I added the flag -Wl,--whole-archive before libnrf52.a . Now we can see that the linker links all objects from the static lib : 
 attempt to open libnrf52.a succeeded
(libnrf52.a)app_error.c.o
(libnrf52.a)app_error_weak.c.o
(libnrf52.a)app_fifo.c.o
(libnrf52.a)app_uart_fifo.c.o
(libnrf52.a)app_util_platform.c.o
(libnrf52.a)boards.c.o
(libnrf52.a)gcc_startup_nrf52840.S.o
(libnrf52.a)nrf_assert.c.o
(libnrf52.a)nrf_balloc.c.o
(libnrf52.a)nrf_drv_common.c.o
(libnrf52.a)nrf_drv_uart.c.o
(libnrf52.a)nrf_log_frontend.c.o
(libnrf52.a)nrf_memobj.c.o
(libnrf52.a)nrf_strerror.c.o
(libnrf52.a)retarget.c.o
(libnrf52.a)system_nrf52840.c.o 
 I also added the -Wl,--no-whole-archive after the library that other libraries won't be affected. The final gcc command is the following : 
 arm-none-eabi-gcc -O3 -mthumb -mabi=aapcs -L ../../../../../../components/toolchain/gcc -Tuart_gcc_nrf52.ld -mcpu=cortex-m4 -mfloat-abi=hard -mfpu=fpv4-sp-d16 --specs=nano.specs main.c.o -Wl,--whole-archive libnrf52.a -Wl,--no-whole-archive -o nrf52840_xxaa.out

Creating a "system" static lib

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