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[webhome] [C++]
GNU Debugger (GDB) Cheat sheet
GDB help can be invoke by typing gdb -help at the terminal screen or type help while debugging.
Preparing the executable for GDB by compiling the code using -g option
| $ g++ -g demo.cpp -o demo |
Compile source code and prepare executable demo for gdb (debugger) |
Invoke GDB debugger by typing gdb executable file
$ gdb demo
(gdb) await GDB command
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Place executable demo in symbolic debugging environment |
GDB Command (short-hand)
run (r) executable filename : run executable
(gdb) r demo
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Run executable demo |
quit (q) : quit GDB
(gdb) q
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Terminate GDB application |
break (b) : set breakpoint at current line
break (b) line : set breakpoint at specified line
break (b) function: set breakpoint at specified function
(gdb) b add_Student
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set break point at function add_Student( ) |
Breakpoint 2 at 0x881131: file student.cc, line 12
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info break : display set breakpoint
(gdb) info break
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display current set breakpoints |
Num Type Disp Enb Address What
1 breakpoint keep y 0x401052 in main() at demo.cc:17
2 breakpoint keep y 0x881131 in add_Student() at student.cc:12
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delete (d) : remove all breakpoints
delete (d) num: remove specified breakpoint from info break output
(gdb) d 2
(gdb) info break
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remove breakpoint #2
display current set breakpoints |
Num Type Disp Enb Address What
1 breakpoint keep y 0x401052 in main() at demo.cc:17
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next (n) or : Execute the code line by line, executing the current line
step (s) and display the next line to be execute.
cont (c) : Continue program execution
print (p) variable : display content of a single variable
(gdb) p student_ID
5340
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Output current value of variable student_ID |
print (p) &variable : display address of the variable
(gdb) p &student_ID
0X80012
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Output address of variable student_ID |
print (p) *pointer : display content of variable the pointer is pointed to
(gdb) p *s_ID
5340
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Output content of varible that the pointer s_IDm pointed to |
(gdb) p s_ID
0X80012
(gdb) p &student_ID
0X80012
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Output value of pointer s_ID
Note
Most error occurs when pointer points to incorrect address of the variable, in
which it should to be pointed to. Software developer/engineer should compare the
address of the variable and the value of the pointer, if the application outputs
garbage or unexpected result. |
set variable = value : assigned value to variable during debugging
(gdb) set student_ID = 5340
5340
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Assigned value of 5340 to variable student_ID |
list (l) function name : display source code begin from the specified funtion name
list (l) line-number : display 10 lines of source code begin from the specified line-number
list (l) from line-number, to line-number : display source code within the inteval requested
(gdb) list 5, 7
5 int *s_ID = &student_ID;
6 char *s_FName;
7 char *s_LName;
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Display source code from line 5 to 7 |
where : display stack trace showing the sequence of function calls with function name and arguments
(gdb) where
#1 main ( ) at demo.cc:17
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Output sequence of function calls with function name and arguments |
info locals : display defined variables and arguments
(gdb) info locals
student_ID = 5340
s_ID = 0X80012 "5340"
s_FName = 0x1100FF "John"
s_LName = 0x1200AF "Doe"
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Display variable and argument values currently defined. |
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