2

I'm curious about what some of my code is being compiled into, is there a way to have the compiler save the intermediate assembly files, ideally somewhere in the project folder? I read some forum posts about holding down shift when compiling from the Arduino IDE, but even that seems pretty hackish.

Bob
  • 185
  • 7

1 Answers1

3

Turn on Verbose Compiling in the Arduino IDE and you will see all the intermediate file names (they are done in a temporary folder).

For example:

/home/nick/Development/arduino-1.6.7/arduino-builder -dump-prefs -logger=machine -hardware "/home/nick/Development/arduino-1.6.7/hardware" -hardware "/home/nick/.arduino15/packages" -hardware "/home/nick/Arduino/hardware" -tools "/home/nick/Development/arduino-1.6.7/tools-builder" -tools "/home/nick/Development/arduino-1.6.7/hardware/tools/avr" -tools "/home/nick/.arduino15/packages" -built-in-libraries "/home/nick/Development/arduino-1.6.7/libraries" -libraries "/home/nick/Arduino/libraries" -fqbn=arduino:avr:uno -ide-version=10607 -build-path "/tmp/build1cdca0d02fcf3112936d1438c170697d.tmp" -warnings=default -prefs=build.warn_data_percentage=75 -verbose "/tmp/arduino_1cdca0d02fcf3112936d1438c170697d/sketch_mar03b.ino"
/home/nick/Development/arduino-1.6.7/arduino-builder -compile -logger=machine -hardware "/home/nick/Development/arduino-1.6.7/hardware" -hardware "/home/nick/.arduino15/packages" -hardware "/home/nick/Arduino/hardware" -tools "/home/nick/Development/arduino-1.6.7/tools-builder" -tools "/home/nick/Development/arduino-1.6.7/hardware/tools/avr" -tools "/home/nick/.arduino15/packages" -built-in-libraries "/home/nick/Development/arduino-1.6.7/libraries" -libraries "/home/nick/Arduino/libraries" -fqbn=arduino:avr:uno -ide-version=10607 -build-path "/tmp/build1cdca0d02fcf3112936d1438c170697d.tmp" -warnings=default -prefs=build.warn_data_percentage=75 -verbose "/tmp/arduino_1cdca0d02fcf3112936d1438c170697d/sketch_mar03b.ino"
"/home/nick/Development/arduino-1.6.7/hardware/tools/avr/bin/avr-g++" -c -g -Os -w -std=gnu++11 -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics  -w -x c++ -E -CC -mmcu=atmega328p -DF_CPU=16000000L -DARDUINO=10607 -DARDUINO_AVR_UNO -DARDUINO_ARCH_AVR   "-I/home/nick/Development/arduino-1.6.7/hardware/arduino/avr/cores/arduino" "-I/home/nick/Development/arduino-1.6.7/hardware/arduino/avr/variants/standard" "/tmp/build1cdca0d02fcf3112936d1438c170697d.tmp/sketch/sketch_mar03b.ino.cpp" -o "/dev/null"
"/home/nick/Development/arduino-1.6.7/hardware/tools/avr/bin/avr-g++" -c -g -Os -w -std=gnu++11 -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics  -w -x c++ -E -CC -mmcu=atmega328p -DF_CPU=16000000L -DARDUINO=10607 -DARDUINO_AVR_UNO -DARDUINO_ARCH_AVR   "-I/home/nick/Development/arduino-1.6.7/hardware/arduino/avr/cores/arduino" "-I/home/nick/Development/arduino-1.6.7/hardware/arduino/avr/variants/standard" "-I/home/nick/Arduino/libraries/PID_v1" "/tmp/build1cdca0d02fcf3112936d1438c170697d.tmp/sketch/sketch_mar03b.ino.cpp" -o "/dev/null"
"/home/nick/Development/arduino-1.6.7/hardware/tools/avr/bin/avr-g++" -c -g -Os -w -std=gnu++11 -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics  -w -x c++ -E -CC -mmcu=atmega328p -DF_CPU=16000000L -DARDUINO=10607 -DARDUINO_AVR_UNO -DARDUINO_ARCH_AVR   "-I/home/nick/Development/arduino-1.6.7/hardware/arduino/avr/cores/arduino" "-I/home/nick/Development/arduino-1.6.7/hardware/arduino/avr/variants/standard" "-I/home/nick/Arduino/libraries/PID_v1" "/home/nick/Arduino/libraries/PID_v1/PID_v1.cpp" -o "/dev/null"
"/home/nick/Development/arduino-1.6.7/hardware/tools/avr/bin/avr-g++" -c -g -Os -w -std=gnu++11 -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics  -w -x c++ -E -CC -mmcu=atmega328p -DF_CPU=16000000L -DARDUINO=10607 -DARDUINO_AVR_UNO -DARDUINO_ARCH_AVR   "-I/home/nick/Development/arduino-1.6.7/hardware/arduino/avr/cores/arduino" "-I/home/nick/Development/arduino-1.6.7/hardware/arduino/avr/variants/standard" "-I/home/nick/Arduino/libraries/PID_v1" "/tmp/build1cdca0d02fcf3112936d1438c170697d.tmp/sketch/sketch_mar03b.ino.cpp" -o "/dev/null"
...
"/home/nick/Development/arduino-1.6.7/hardware/tools/avr/bin/avr-ar" rcs  "/tmp/build1cdca0d02fcf3112936d1438c170697d.tmp/core/core.a" "/tmp/build1cdca0d02fcf3112936d1438c170697d.tmp/core/main.cpp.o"
"/home/nick/Development/arduino-1.6.7/hardware/tools/avr/bin/avr-ar" rcs  "/tmp/build1cdca0d02fcf3112936d1438c170697d.tmp/core/core.a" "/tmp/build1cdca0d02fcf3112936d1438c170697d.tmp/core/new.cpp.o"
"/home/nick/Development/arduino-1.6.7/hardware/tools/avr/bin/avr-gcc"  -Os -Wl,--gc-sections -mmcu=atmega328p  -o "/tmp/build1cdca0d02fcf3112936d1438c170697d.tmp/sketch_mar03b.ino.elf" "/tmp/build1cdca0d02fcf3112936d1438c170697d.tmp/sketch/sketch_mar03b.ino.cpp.o" "/tmp/build1cdca0d02fcf3112936d1438c170697d.tmp/libraries/PID_v1/PID_v1.cpp.o" "/tmp/build1cdca0d02fcf3112936d1438c170697d.tmp/core/core.a" "-L/tmp/build1cdca0d02fcf3112936d1438c170697d.tmp" -lm
"/home/nick/Development/arduino-1.6.7/hardware/tools/avr/bin/avr-objcopy" -O ihex -j .eeprom --set-section-flags=.eeprom=alloc,load --no-change-warnings --change-section-lma .eeprom=0  "/tmp/build1cdca0d02fcf3112936d1438c170697d.tmp/sketch_mar03b.ino.elf" "/tmp/build1cdca0d02fcf3112936d1438c170697d.tmp/sketch_mar03b.ino.eep"
"/home/nick/Development/arduino-1.6.7/hardware/tools/avr/bin/avr-objcopy" -O ihex -R .eeprom  "/tmp/build1cdca0d02fcf3112936d1438c170697d.tmp/sketch_mar03b.ino.elf" "/tmp/build1cdca0d02fcf3112936d1438c170697d.tmp/sketch_mar03b.ino.hex"
Using library PID_v1 in folder: /home/nick/Arduino/libraries/PID_v1 (legacy)

Sketch uses 6,484 bytes (20%) of program storage space. Maximum is 32,256 bytes.
Global variables use 285 bytes (13%) of dynamic memory, leaving 1,763 bytes for local variables. Maximum is 2,048 bytes.

Of interest are the last couple - the xxx.elf file and the xxx.hex file (where xxx is your sketch name).

The xxx.hex file is what is uploaded to your Arduino (well, it is decoded by Avrdude).

The xxx.elf file can be used to get assembly output, like this:

avr-objdump -Sz xxx.elf

That outputs to the screen. I usually output to a file:

avr-objdump -Sz xxx.elf > /tmp/avr_dump.txt

Example output:

void setup() {
      ec:   0f 93           push    r16
      ee:   1f 93           push    r17
  Setpoint = 100;
      f0:   80 e0           ldi r24, 0x00   ; 0
      f2:   90 e0           ldi r25, 0x00   ; 0
      f4:   a8 ec           ldi r26, 0xC8   ; 200
      f6:   b2 e4           ldi r27, 0x42   ; 66
      f8:   80 93 73 01     sts 0x0173, r24
      fc:   90 93 74 01     sts 0x0174, r25
     100:   a0 93 75 01     sts 0x0175, r26
     104:   b0 93 76 01     sts 0x0176, r27
  //turn the PID on
  myPID.SetMode(AUTOMATIC);
     108:   61 e0           ldi r22, 0x01   ; 1
     10a:   70 e0           ldi r23, 0x00   ; 0
     10c:   82 e3           ldi r24, 0x32   ; 50
     10e:   91 e0           ldi r25, 0x01   ; 1
     110:   0e 94 04 04     call    0x808   ; 0x808 <_ZN3PID7SetModeEi>

In this particular case Setpoint was a double so it took 8 instructions to load a literal into it.

Nick Gammon
  • 38,901
  • 13
  • 69
  • 125