Debugging

Usually, a compiled executable does not have references of either source-code variable names or line numbers. However, an executable compiled for debugging retains these references. This allows:

program tracing - suspend the execution of the program when it reaches a specified line (called breakpoint) in the source file or even suspend it after every line. Thus allowing line by line execution.
variable lookup - observe the values of the variables.

Debugging in GCC is done using a command line debugger called gdb. CDT of Eclipse provides a graphics front end to gdb. By default, CDT compiles all programs ready for debugging.

To debug a built program, press F11 or click on debug icon on the CDT toolbar. This opens a debug perspective. Debug perspective has several major views.

Variables view shows the values of the variables.
Editor view shows the source program with the line where the execution is suspended highlighted.
Debug view shows the status of debugging.

By default. The debugged program automatically suspends in the first statement of the main function.

Hitting key F6 or clocking on the appropriate icon on the toolbar in debug view, advances the program execution exactly one line. Repeatedly "stepping over" the lines of the program in this fashion allows the programmer to trace the program execution in detail.

Note that cygwin does not interact with standard Eclipse console well. Therefore, for debugging, CDT launches a separate window for input and output.

Note also that cygwin debugger could not find source files by default. Which means that when you run debugger for the first time, the debugger may not show the source code. To fix that, follow the directions here

Breakpoints

Breakpoint is a line in the program where the execution stops. Tracing the program step-by-step may become tedious, especially if the program is large. Instead a breakpoint may be set at the particular line of interest. To add a breakpoint in Eclipse, double click the marker bar located on the left margin of the editor view beside the line of code where you want to add a breakpoint. A blue dot is displayed in the marker bar and in the Breakpoints view, along with the name of the associated file. To clear (remove) a breakpoint, double-click on the blue dot associated with it.

Displaying Arrays in Functions

After array is passed to a function as a parameter, its size information is lost. The debugger cannot present the array contents properly. To display the array information, right-click on the array name and choose: "Display As Array" option. A dialog box appears prompting you to enter the first index and the array size. Henceforward, Eclipse will display this array with the size specified. To change the size of this array or undo this modification right-click on the array name and select "Restore Original Type".