Removing Dead Code

Last week I was working on code coverage.  One of the results I saw is that some of the source code we own is not used by any of our testing - it is 0% covered.  Digging into this, I found out that this code is not used at all by Tableau so I intend to start removing it from our codebase.

Code that is not used by the product you are working on is often referred to as  "dead code" and there are a few ways this can happen.  One obvious way is that existing code functionality simply gets provided by something else.  Let's say you had a very slow Bubble Sort routine to sort a list.  Once you learn a faster algorithm to sort, like Quick Sort, you start using the Quick Sort instead.  If you are not diligent when making the code change to use Quick Sort, the Bubble Sort code can get left behind.  It is not used at this point and becomes "dead code."

Similarly, if you need to implement sorting, you could try Quick Sort, Insertion Sort and Merge Sort (for instance).  Once you profile the time spent by each routine and generate the test data, you can make a decision about which routine to use.  Again, if you don't remove the routines you don't use, they become "dead code." 

After digging into the code coverage numbers, I found a few instances of the second case.  Since this code is not used at all, it doesn't get compiled so that helps mitigate having it around.  But it still results in a good amount of unneeded code stored on everyone's hard drive, maintained in our repository and so on.  The best practice is to just get rid of it and that is what I am working on now.

Questions, comments, concerns and criticisms always welcome,

John

Working on a code coverage task this week

For this week I am focused on getting code coverage numbers for our team.

Challenge #1 is pretty simple to state - get a list of all the source files that our team owns.  And while the problem is easy to understand, the real world implications of this are a bit trickier, especially with older files we have.  As the years have gone by, ownership of unchanging source files gets a little fuzzy.  The team (or developer) who created the original source file may be long gone.  Even teams that own a file might have been reorganized - several times over - since the file was checked in. 

So if Carol created the original "stats.cpp" file she may be the only person to ever have edited it.  If she moves to another team, and her old team gets reorganized, ownership can get moved to the bottom of the list of problems to address at that point.  After all, if the code is stable, why spend resources on tracking who should be associated with it? 

But after a while, every company has this challenge.  That is what I am sorting out this week.

Fortunately, Tableau has been pretty good with naming conventions for source files.  For example, all Cluster related files have the text "cluster" in them.  For most of the features my team owns, I can simply search by file name to get a good starting point for the files we own.  Getting that list together, parsed and cleaned up is my goal for the week.

After that, I think I may need to move to class based ownership.  More on that next time.

Questions, comments, concerns and criticisms always welcome,

John

A nifty site to see what a compiler does to C++ code

While investigating a very intermittent unit test failure this week, I noticed an anomaly in our code.  This test is written in c++ and had an extra semicolon in it:

We had a test that did something like this:

Worksheet wb = wbc->GetSheet();

    ;

 CPPUNIT_ASSERT(blah blah);

Notice that extra ; in the middle?  Since the test intermittently fails, I was looking for anything unexpected in the code.  This is unexpected, but I also needed to know if it was important.

Matt Godbolt created a terrific site that lets you put in C++ code and see what output various compilers produce.  The site is here  https://gcc.godbolt.org/

You can choose different compilers and I just took a look at gcc 6.3 to see if it would ignore an extra ;. 

Here's my test code:

void test()

{

int x=1;

;

}

And here is the output:

        push    rbp

        mov     rbp, rsp

        mov     DWORD PTR [rbp-4], 1

        nop

        pop     rbp

        ret

I get the same output with or without the extra semicolon. This is great since I would expect the compiler to get rid of blank commands like this.  Since the compiler does indeed ignore this typo in the code, I can move on to other avenues of investigation.

Give this site a whirl.  You can choose several different compilers and chip options, pass parameters in and so on.  Thanks Matt!

Questions, comments, concerns and criticisms always welcome,

John

Always learning

One of the most fun aspects (to me) of being in the world of software development is the focus on continual learning.  The systems on which we work are constantly evolving.

For instance, when I started way back in 1995, Windows 3.1 was the dominant OS.  Smart phones did not exist, tablets were only on Star Trek and so on.  The challenge is how to adapt to a constantly changing world.

The strategy I use is one of constant learning.  MOOCs have made this much easier in the last few years - I tend to prefer a combination of lectures and hands on to learn a new skill.  To me, which new skill to learn is not as important as always learning something.  Sometimes there is a skill I need to learn that is very relevant to some project that is upcoming - for instance, learning Python because our automation system here at Tableau uses Python is an obvious example.

But other times I take on tasks that are more in a hobby space.  To this end, for the past few months I have been enrolled in a Programming the Internet of Things program at Coursera.  It has been a blast!  It made me brush up on electronics I learned years ago in the navy as well as some programming in C and Python.  I got to work with the Raspberry Pi and Arduino, install some useful libraries and my final capstone was a device that would email me if I left my garage door in my house was left open.  This was a beginner level class so the introduction was very gentle and definitely left me wanting more.

I received my final certificate this last week and am thinking about going deeper into another class.  Either that or finish the growing list of project ideas I developed while taking this class.  Either way, it should be fun!

Questions, comments, concerns and criticisms always welcome,

John