Looking at code generated by Arduino compiles

Most of the time you don’t need to do this.  But, if you are writing real-time code that is time sensitive or if you interested in what the compiler did with your C or C++, then this is for you.

You may have noticed that when you create a new SketchBook you get a new folder that has the name of the Sketch.  Inside of this folder is another folder that is named “applet”.  This applet folder is created by a successful compile of the Sketch AND a successful upload to the Arduino board.  In the applet folder there are several files, but the ones we are interested in are the ones with the “.o” file name suffixs.  These are the individual object files created by the compiler.  Each one of these correspond to an associated C/C++ source.  As you will notice, there are more in the folder than you probably wrote.  These additional files are all of the other arduino associated files that complete your application.

These object files are binary.  Fortunately, there is another program supplied by the Arduino system that permits looking at a textual version of those files.   The “objdump” executable found in the \hardware\tools\avr\avr\bin\ area of your arduino installation folder.  This program reads an object file (.o) and creates a text file.  To make it easy, create a batch file, I called it objdump.bat.  I put the single following line into this batch file:

for %%f in (*.o) do C:\arduino-0012\hardware\tools\avr\avr\bin\objdump -S %%f > %%~nf.txt

(Please ignore the extra spaces created in the blog)   Of course you also need to change the path to the program to match where you have it located (C:\arduino….)

Ok, now after you have uploaded to the arduino, copy the batch file into the applet folder.  The reason for a copy is that this folder is deleted and recreated everytime you do another upload – hence, you have to have the batch file somewhere else and copy eacy time.  Run the batch file and you should see several new files of type .txt.  Each of these new files are then viewable to see both the original source code and the assocated assembly statements.

Enjoy.

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One Response to “Looking at code generated by Arduino compiles”

  1. Chris Says:

    Thanks! You saved me about an hour trying to figure this out on my own!

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