Fixing Segmentation faults in C++

1. Compile your application with -g, then you'll have debug symbols in the binary file.

2. Use gdb to open the gdb console.

3. Use file and pass it your application's binary file in the console.

4. Use run and pass in any arguments your application needs to start.

5. Do something to cause a Segmentation Fault.

6. Type bt in the gdb console to get a stack trace of the Segmentation Fault.

Before the problem arises, try to avoid it as much as possible:

• Compile and run your code as often as you can. It will be easier to locate the faulty part.
• Try to encapsulate low-level / error prone routines so that you rarely have to work directly with memory (pay attention to the modelization of your program)
• Maintain a test-suite. Having an overview of what is currently working, what is no more working etc, will help you to figure out where the problem is (Boost test is a possible solution, I don't use it myself but the documentation can help to understand what kind of information must be displayed).

Use appropriate tools for debugging. On Unix:

• GDB can tell you where you program crash and will let you see in what context.
• Valgrind will help you to detect many memory-related errors.
• With GCC you can also use mudflap With GCC, Clang and since October experimentally MSVC you can use Address/Memory Sanitizer. It can detect some errors that Valgrind doesn't and the performance loss is lighter. It is used by compiling with the-fsanitize=address flag.

Finally I would recommend the usual things. The more your program is readable, maintainable, clear and neat, the easiest it will be to debug.

Sometimes the crash itself isn't the real cause of the problem-- perhaps the memory got smashed at an earlier point but it took a while for the corruption to show itself. Check out valgrind, which has lots of checks for pointer problems (including array bounds checking). It'll tell you where the problem starts, not just the line where the crash occurs.