[eric.m.tridas]

Hi Guys,

I've been programming a library lately and ran into a seemingly impossible to find bug. I had been stuck for days when I decided to do fresh OF install with debugging enabled. After this install I recompiled my library and went to test it and it worked fine! This was very confusing to me and although I am happy the bug has seemingly disappeared I still want to know what the issue was.

Has anyone else ever ran into this type of issue?

Thanks,

Eric

[wyldckat]

Greetings Eric,

Perhaps you've tripped on an Heisenbug? http://en.wikipedia.org/wiki/Heisenbug

From your description, that sort of bug usually happens because the programmer is not being careful enough with every single compilation step. For example:

• If you did not rename the utility/solver/library in "Make/files" early enough during your development, you might be getting not one but 2 binaries of the same name in different paths. Try running:
  

  ls -l $FOAM_USER_LIBBIN/libMyCustomLibrary.so
  ls -l $FOAM_LIBBIN/libMyCustomLibrary.so

  er, rename "libMyCustomLibrary" for your library's name - if the file exists at both locations, then only one of them is being picked up at loading time.
• "libMyCustomLibrary" and "libmyCustomLibrary" is not the same thing!!! Notice the lower case "m"? That's more than enough for a problem.
• Somewhat less common are issues related to initialization of variables. Assuming that a variable always starts with zero when it's created, e.g:
  

  scalar myArea;

  this is extremely risky, since it might start off with "1.31242316e-234" instead of 0

Beyond this, the rule is usually simple and common to many professions, may it be for chefs, mechanics, programmers, laboratory scientists, and even any calculator users: always make sure you know and understand the initial conditions you're using, i.e. always keep your workbench clean!!

Best regards,
Bruno