复旦大学软件学院计算机系统课件 Use GDB to Debug a Program.ppt

How to Debug a Program ICS2012 2012-5-2 Outline Introduction Basic commands Instruction level debug Source level debug What can debuggers do? Run programs Make the program stops on specified places or on specified conditions Give information about current variables’ values, the memory and the stack Let you examine the program execution step by step - stepping Let you examine the change of program variables’ values - tracing GDB: Basic Commands Start Up Method 1 $ gdb my_prog //my_prog is your executable file name! Method 2 $ gdb (gdb) file my_prog Stop (gdb) kill Quit (gdb) quit Shell (gdb) shell command //”shell ls” to list the current directory GDB: Basic Commands Get help Offline $ info gdb GDB user manual GDB reference card Online (gdb) help command Command Use TAB to complete Use up/down arrow to select GDB: Basic Commands (gdb) help List of classes of commands: aliases -- Aliases of other commands breakpoints -- Making program stop at certain points data -- Examining data files -- Specifying and examining files internals -- Maintenance commands obscure -- Obscure features running -- Running the program stack -- Examining the stack status -- Status inquiries GDB: Basic Commands (gdb) help stack Examining the stack. The stack is made up of stack frames. Gdb assigns numbers to stack frames counting from zero for the innermost (currently executing) frame. … … List of commands: backtrace -- Print backtrace of all stack frames frame -- Select and print a stack frame … Debug: Source Code #includestdio.h void swap(long *a, long *b){ long temp; temp = *a; *a = *b; *b = temp; } void main(void) { long a[2]; a[0] = 0x1000000; a[1] = 0x0000001; printf(a[0] and a[1] are 0x%x and 0x%x.\n,a[0],a[1]); swap(a[0],a[1]); printf(after swap:\n); printf(a[0] and a[1] are 0x%x and 0x%x.\n,a[0],a[1]); } Debug a Program Run a program (gdb) run/r Set a breakpoint to pause program break/b main //stop at main function Resume (g