Note: The example program used in this section, adbsamp3, contains an infinite recursion of subfunction calls. If you run this program to completion, it causes a memory fault error and quits.
The following example shows how to execute a program under adb control and carry out the basic debugging operations described in the following sections.
The source program for this example is stored in a file named adbsamp3.c. Compile this program to an executable file named adbsamp3 using the cc command:
cc adbsamp3.c -o adbsamp3
To start the session and open the program file, use the following command (no core file is used):
adb adbsamp3
First, set breakpoints at the beginning of each function using the :b subcommand:
.f:b .g:b .h:b
Next, display the first five instructions in the f function:
.f,5?ia .f: .f: mflr r0 .f+4: st r0, 0x8(r1) .f+8: stu r1, -64(r1) .f+c: st r3, 0x58(r1) .f+10: st r4, 0x5c(r1) .f+14:
Display five instructions in function g without their addresses:
.g,5?i
.g: mflr r0
st r0, 0x8(r1)
stu r1, -64(r1)
st r3, 0x58(r1)
st r4, 0x5c(r1)
Start the program by entering the following command:
:r adbsamp3: running breakpoint .f: mflr r0
The adb program runs the sample program until it reaches the first breakpoint where it stops.
Since running the program to this point causes no errors, you can remove the first breakpoint:
.f:d
Use the :c subcommand to continue the program:
:c adbsamp3: running breakpoint .g: mflr r0
The adb program restarts the adbsamp3 program at the next instruction. The program operation continues until the next breakpoint, where it stops.
Trace the path of execution by entering:
$c .g(0,0) .f+2a .f(1,1) .main+e .main(0,0,0) start+fa
The $c subcommand displays a report that shows the three active functions: main , f and g .
Display the contents of the fcnt integer variable by entering the command:
fcnt/D fcnt: fcnt: 1
Next, continue running the program and skip the first 10 breakpoints by entering:
,10:c adbsamp3: running breakpoint .g: mflr r0
The adb program starts the adbsamp3 program and displays the running message again. It does not stop the program until exactly 10 breakpoints have been encountered. To ensure that these breakpoints have been skipped, display the backtrace again:
$c .g(0,0) .f+2a .f(2,11) .h+28 .h(10,f) .g+2a .g(11,20) .f+2a .f(2,f) .h+28 .h(e,d) .g+2a .g(f,1c) .f+2a .f(2,d) .h+28 .h(c,b) .g+2a .g(d,18) .f+2a .f(2,b) .h+28 .h(a,9) .g+2a .g(b,14) .f+2a .f(2,9) .h+28 .h(8,7) .g+2a .g(9,10) .f+2a .f(2,7) .h+28 .h(6,5) .g+2a .g(7,c) .f+2ae .f(2,5) .h+28 .h(4,3) .g+2a .g(5,8) .f+2a .f(2,3) .h+28 .h(2,1) .g+2a .g(2,3) .f+2a .f(1,1) .main+e .main(0,0,0) start+fa
Displaying and Manipulating the Source File with the adb Program.
Example adb Program: adbsamp2.
Example adb Program: adbsamp3.