Debugging with GDB (September 2007)

168 Debugging with GDB
14.17 Aborting a Command Line Call
When a command line call is issued and it is interrupted by a breakpoint or a signal
before completing the program execution, the abort command enables the user to
abort the command line call without allowing the signal to modify the state of the
debugged process.
When a signal interrupts program execution, it can modify the process state of the de-
bugged program and result in an abrupt termination of the program (due to addressing
errors from a call that is not a part of the source program). In such cases, the abort
command is particularly useful in exiting the command line call without modifying the
process state of the debugged program.
The following example illustrates the use of the abort command:
(gdb) break main
Breakpoint 1 at 0x2c74: file .../address_error.c, line 41.
(gdb) run
Starting program: ./address_error
Breakpoint 1, main () at ./address_error.c:41
41 fun (count, count*1.1);
(gdb) p fun(10, 1.1)
Program received signal SIGBUS, Bus error
si_code: 0 - BUS_UNKNOWN - Unknown Error.
0x2c38 in fun (i=10, f=0) at ./address_error.c:37
37 count = *p;
The program being debugged was signaled while in a function called from GDB.
GDB remains in the frame where the signal was received.
To change this behavior use "set unwindonsignal on"
Evaluation of the expression containing the function (fun) will be abandoned.
(gdb) bt
#0 0x2c38 in fun (i=10, f=0) at ../address_error.c:37
#1 0x1920 in _sr4export+0x8 ()
#2 <function called from gdb>
#3 0x2c74 in main () at ./address_error.c:40
(gdb) abort
Abort gdb command line call? (y or n) y
#0 main () at ./address_error.c:41
41 fun (count, count*1.1);
(gdb) bt
#0 main () at ./address_error.c:41
(gdb) quit
The program is running. Exit anyway? (y or n) y
14.18 Instruction Level Stepping
During instruction level stepping with nexti and stepi, WDB prints the assembly
instruction along with the next source line.