Summary

• GNU includes software called a debugger, which allows you to monitor the execution of your programs to locate and remove logic errors.
• The GNU debugger works only with executable files that were compiled with the -g compiler option, which generates information that is used by the debugger to help you debug your programs.
• The gdb command will start the GNU debugger and enable you to use its features. The run command will run a program through the debugger.
• Breakpoints are markers that can be set at any executable line of code. When program execution reaches a breakpoint, execution pauses.
• The break command inserts a breakpoint at the line number specified after the command.
• When the program runs, it suspends execution at any line that contains a breakpoint and is said to be in break mode.
• The continue command causes the program to continue running until the next breakpoint is reached.
• The print command allows you to peek inside the computer at the value of one of your variables.
• When the print command is used, the result is stored in a convenience variable such as $1. Convenience variables are temporary variables that can be used in the debugging process to perform arithmetic and evaluate boolean expressions.
• You can display a list of all of the breakpoints in the program by typing info break.
• To remove a breakpoint, type delete, followed by a space and the number of the breakpoint to remove.
• Use the quit command to end the debugging session.
• The set command allows the programmer to assign new values to variables.
• The step command executes the next statement in the program. If the next statement to execute is a function call, control transfers to the called function. The step command enables you to enter a function and study the individual statements of that function.
• The finish command executes the remaining statements in the function and returns control to the place where the function was called.
• The next command behaves like the step command, except when the next statement to execute contains a function call. In that case, the called function executes in its entirety and the program advances to the next executable line after the function call.
• The watch command sets a watch on any variable or data member of an object currently in scope during execution of the debugger. Whenever the value of a watched variable changes, the debugger enters break mode and notifies you that the value has changed.