On Saturday, 11 August 2012 at 23:49:18 UTC, Chad J wrote:
On 08/10/2012 06:01 PM, Walter Bright wrote:
It catches only a subset of these at compile time. I can craft
any number of ways of getting it to miss diagnosing it.
Consider this one:
float z;
if (condition1)
z = 5;
... lotsa code ...
if (condition2)
z++;
To diagnose this correctly, the static analyzer would have to
determine that condition1 produces the same result as
condition2, or not. This is impossible to prove. So the static
analyzer either gives up and lets it pass, or issues an
incorrect diagnostic. So our intrepid programmer is forced to
write:
float z = 0;
if (condition1)
z = 5;
... lotsa code ...
if (condition2)
z++;
Now, as it may turn out, for your algorithm the value "0" is
an out-of-range, incorrect value. Not a problem as it is a
dead assignment, right?
But then the maintenance programmer comes along and changes
condition1 so it is not always the same as condition2, and now
the z++ sees the invalid "0" value sometimes, and a silent bug
is introduced.
This bug will not remain undetected with the default NaN
initialization.
Let's keep in mind everyone of these truths:
1) Programmers are lazy; If you can get away with not
initializing something then you'll avoid it. In C I've failed to
initialized variables many times until a bug crops up and it's
difficult to find sometimes, where a NaN or equiv would have
quickly cropped them out before running with any real data.
2) There are a lot of inexperienced programmers. I worked for a
company for a short period of time that did minimal training on a
language like Java, where I ended up being seen as an utter
genius (compared to even the teachers).
3) Bugs in a large environment and/or scenarios are far more
difficult if not impossible to debug. I've made a program that
handles merging of various dialogs (using double linked-like
lists); I can debug them if they are 100 or less to work with,
but after 100 (and often it's tens of thousands) it can become
such a pain based on it's indirection and how the original
structure was built that I refuse based on difficulty vs end
results (Plus sanity).
We also need to sometimes laugh at our mistakes, and learn from
others. I'll recommend everyone read from rinkworks a bit if you
have the time and refresh yourselves.
http://www.rinkworks.com/stupid/cs_programming.shtml
