AVR-GCC Makefile Linking Issue

Question

I've got the following Makefile:

# Name: Makefile
# Author: <insert your name here>
# Copyright: <insert your copyright message here>
# License: <insert your license reference here>

# DEVICE ....... The AVR device you compile for
# CLOCK ........ Target AVR clock rate in Hertz
# OBJECTS ...... The object files created from your source files. This list is
#                usually the same as the list of source files with suffix ".o".
# PROGRAMMER ... Options to avrdude which define the hardware you use for
#                uploading to the AVR and the interface where this hardware
#                is connected.
# FUSES ........ Parameters for avrdude to flash the fuses appropriately.

CSRC       = main.c Sys_init.c BB_Timers.c SPI.c Radio_interface.c  
DEVICE     = atmega328p 
MCU        = m328p 
CLOCK      = 800000
PROGRAMMER = -c dragon_isp 
PORT       = -P usb 
#PROGRAMMER = -c /dev/buspirate 
OBJECTS    = main.o 
FUSES      = -U efuse:w:0xff:m -U lfuse:w:0xe2:m -U hfuse:w:0xde:m
OBJECTS    = $(CSRC:.c=.o) $(ASRC:.s=.o)


######################################################################
######################################################################

# Tune the lines below only if you know what you are doing:

AVRDUDE = avrdude $(PROGRAMMER) $(PORT) -p $(DEVICE) -vv
COMPILE = avr-gcc -Wall -Os -DF_CPU=$(CLOCK) -mmcu=$(DEVICE) # symbolic targets:
all:    main.hex

.c.o:
    $(COMPILE) -c $< -o $@

.S.o:
    $(COMPILE) -x assembler-with-cpp -c $< -o $@
# "-x assembler-with-cpp" should not be necessary since this is the default
# file type for the .S (with capital S) extension. However, upper case
# characters are not always preserved on Windows. To ensure WinAVR
# compatibility define the file type manually.

.c.s:
    $(COMPILE) -S $< -o $@

flash:  all
    $(AVRDUDE) -U flash:w:main.hex:i

fuse:
    $(AVRDUDE) $(FUSES)

install: flash fuse

# if you use a bootloader, change the command below appropriately:
load: all
    bootloadHID main.hex

clean:
    rm -f main.hex main.elf $(OBJECTS)

# file targets:
main.elf: $(OBJECTS)
    $(COMPILE) -o main.elf $(OBJECTS)

main.hex: main.elf
    rm -f main.hex
    avr-objcopy -j .text -j .data -O ihex main.elf main.hex
# If you have an EEPROM section, you must also create a hex file for the
# EEPROM and add it to the "flash" target.

# Targets for code debugging and analysis:
disasm: main.elf
    avr-objdump -d main.elf

cpp:
    $(COMPILE) -E main.c

When I compile with make, I get the following error:

>> make    
avr-gcc -Wall -Os -DF_CPU=800000 -mmcu=atmega328p   -o main.elf main.o Sys_init.o BB_Timers.o SPI.o Radio_interface.o 
    Sys_init.o: In function `System_init':
    Sys_init.c:(.text+0x0): undefined reference to `One'
    Sys_init.c:(.text+0x2): undefined reference to `One'
    BB_Timers.o: In function `__vector_14':
    BB_Timers.c:(.text+0x2e): undefined reference to `One'
    BB_Timers.c:(.text+0x30): undefined reference to `One'
    collect2: error: ld returned 1 exit status
    make: *** [Makefile:66: main.elf] Error 1

I've tried shuffling the CSRC order around, and that used to seem to make a difference, but not this time. I feel like this is wrong though, because how would someone with many many source files handle this for, say, a big project? There must be a better way.

Answer 1

So summarizing the comments on the question:

In bb_system.h on line 25 you put this statement:

extern struct bb_system One;

This means that somewhere in your compiled files there must be a variable called One of type struct bb_system

And in Sys_init.c on line 7 you commented out the statement

// struct bb_system One;

Which it probably would have resolved to.

Fix that line