Debugging in C Guidelines

Finding Bugs

To find bugs in your code, follow the steps below.

If you are getting a segmentation fault, check your code using Valgrind or gdb. This will help you identify the line where the problem is taking place.
Make sure you are generating the expected results by using diff. In some cases a single character could make you fail a test.
If your code generates the expected results in grace, but not in the submit server try Valgrind. Valgrind can help you identify the use of uninitialized variables and problems with dynamic memory allocation. You can also try to set to 0 uninitialized variables and pointer variables to NULL. This could help you track the problem.
Run splint on your code. For example, splint my_prog.c.
Compile your code with the gcc option -fsanitize=address (e.g., gcc -fsanitize=address p2.c). When you run the code you could get some diagnostic information. If you are running valgrind on your code, probably you should not compile your code with this option.
If none of the above steps identify the problem, try the following:
- Simplify the input/case that is generating the problem.
- Once you have simplified the input/case, use the debugger (gdb) to step through your code. Information on gdb basics can be found at gdb.

Frequently Seen C Mistakes

A list of frequently seen mistakes can be found at mistakes.

Development Strategy for C Programs