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Topic: Get Compiler to Output Assembly (Read 6579 times) previous topic - next topic


How can I tell the compiler to output a assembly file?
Freelance engineer, consultant, contractor. Graduated from UW in 2013.


What I do to look at assembler is use "objdump" on the elf file.  Just connect to the temporary directory that arduino uses for builds (/tmp/build* on my mac) and do something like:
Code: [Select]
MacOSX<1105> cd /tmp/build25808.tmp/
MacOSX<1106> /Downloads/arduino-0008/tools/avr/bin/avr-objdump -S hptime.elf

In theory, there's a -S switch for the compiler as well, but I worry about getting all the right switches and preprocessing done (automatically provided by audino environment), and using the .elf avoids this, and objdump produces a pretty nice mixed source/assembly listing:
Code: [Select]
       Serial.print("millis = ");
12a:   60 e0           ldi     r22, 0x00       ; 0
12c:   71 e0           ldi     r23, 0x01       ; 1
12e:   86 e2           ldi     r24, 0x26       ; 38
130:   91 e0           ldi     r25, 0x01       ; 1
132:   0e 94 ec 00     call    0x1d8 <_ZN14HardwareSerial5printEPKc>
136:   b8 01           movw    r22, r16
138:   a7 01           movw    r20, r14
13a:   86 e2           ldi     r24, 0x26       ; 38
13c:   91 e0           ldi     r25, 0x01       ; 1
13e:   0e 94 2a 01     call    0x254 <_ZN14HardwareSerial5printEm>
       Serial.print(",  high precision time = ");
142:   6a e0           ldi     r22, 0x0A       ; 10
144:   71 e0           ldi     r23, 0x01       ; 1
146:   86 e2           ldi     r24, 0x26       ; 38
148:   91 e0           ldi     r25, 0x01       ; 1
14a:   0e 94 ec 00     call    0x1d8 <_ZN14HardwareSerial5printEPKc>
14e:   dc 2c           mov     r13, r12
150:   cb 2c           mov     r12, r11
152:   ba 2c           mov     r11, r10
154:   aa 24           eor     r10, r10


can someone please .. repost the steps to have the compiler or the sketch invoriment   output the writen C code in assembly .. which the atmel chips understand ..

in an  ( idiot proff way please for the arudino 0017 enviorment

am running windows vista


I am running the Arduino 18 software on Mac OS X, and I don't see any way to get the object code.  I even tried editing Library/Arduino/preferences.txt to change

That did not produce any new files that I could see when I compiled.  Even if it did, the Arduino 18 download does not contain any of the utilities described for looking at the output.  Do I have to get the Arduino source code and build the whole thing from scratch to get the utility files?

Normally C would be fine for me, but I was doing some timing of interrupt routines, and found that accessing a memory location was taking 15 cycles, while the hardware datasheet indicates that it should be taking 2 cycles.  I want to know what code the compiler is generating (I'll replace it with asm code if it is too ridiculous).


Aug 17, 2010, 10:19 am Last Edit: Aug 17, 2010, 10:19 am by mpeuser Reason: 1
Press the SHIFT key when Compiling your code. You then will see in the message window where the system hides it. In Windows, its something like:

documents..\user\local settings...\temp\another temp

Also handy for getting the hex files.


Thanks.  The tools were hidden in
and the intermediate files in

The tools I should have been able to find, despite being hidden from the Finder (I had not dived deep enough into the Arduino.app directory), but the temporary directory was a complete mystery.

Now I can finally find out why the code is taking almost twice as long as I think it should for memory accesses!

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