How to find out where floating point exception occured?

Question

I am currently using a large computational package written in c++, which I have downloaded from github and compiled myself as I want to use it for some work I am doing.

The code works well for most purposes. Unfortunately, I have found that for certain inputs the code gives the error: Floating point exception (core dumped)

Now, I am a beginner at c++ and I have had no luck trying to browse through the many scripts that make up the code. My question is therefore: Is there a simple way to get a c++ code to output which line and which script the error occurred? Being used to Python, this is where I would always start, but unfortunately the compiled code does not return any more details about the error. Do I need to compile it in a form of debugging mode to get it to do so?

Answer 1

Yes, you should build the program in debug mode and run it through a debugger. It'll "break" when the error happens and tell you exactly what line of code triggers it. Furthermore, you can examine the values of variables in that stack frame and lower to diagnose the cause of the problem.

In fact, while developing, you should be doing this anyway.

It is impossible to give general steps as to how to do this, but if you're using an IDE (Visual Studio, Xcode) this should automatically happen; if you're using GCC on the command line, research GDB; if you're using Clang on the command line, research LLDB.

Speaking generally, though, a Floating-Point Exception (not a C++ exception!) is usually, and perhaps confusingly, triggered by an integer division by zero. Though, there are other reasons it can occur. You'll know more once you're debugging.