$ g++ test.cpp -o test -g
$ gdb test
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Reading symbols from test...done.
(gdb) l
1	#include <iostream>
2	
3	int sum(const int& a, const int& b) {
4	    int tmp_sum = a + b;
5	    return tmp_sum;
6	} 
7	 
8	int main() {
9	    int a = 1, b = 2;
10	    a = b;
(gdb) l
11	    int c = sum(a, b);
12	    std::cout << "sum is " << c << std::endl;
13	    return 0;
14	}
(gdb) l
Line number 15 out of range; test.cpp has 14 lines.
(gdb) break 10
Breakpoint 1 at 0x40094d: file test.cpp, line 10.
(gdb) info break
Num     Type           Disp Enb Address            What
1       breakpoint     keep y   0x000000000040094d in main() at test.cpp:10
(gdb) dele[K[K[K[Kr
Starting program: /home/SENSETIME/zhushengfa/ws/c_test/test 

Breakpoint 1, main () at test.cpp:10
10	    a = b;
(gdb) p a
$1 = 1
(gdb) p b
$2 = 2
(gdb) s[Kn
11	    int c = sum(a, b);
(gdb) p a
$3 = 2
(gdb) p b
$4 = 2
(gdb) s
sum (a=@0x7fffffffd82c: 2, b=@0x7fffffffd830: 2) at test.cpp:4
4	    int tmp_sum = a + b;
(gdb) p su[K[Ktmp_sum
$5 = 0
(gdb) p a
$6 = (const int &) @0x7fffffffd82c: 2
(gdb) s
5	    return tmp_sum;
(gdb) p tmp_sum
$7 = 4
(gdb) p &tmp_sum
$8 = (int *) 0x7fffffffd80c
(gdb) p &a
$9 = (const int *) 0x7fffffffd82c
(gdb) s
6	} 
(gdb) s
main () at test.cpp:12
12	    std::cout << "sum is " << c << std::endl;
(gdb) p &a
$10 = (int *) 0x7fffffffd82c
(gdb) n
sum is 4
13	    return 0;
(gdb) n
14	}
(gdb) n
__libc_start_main (main=0x400928 <main()>, argc=1, argv=0x7fffffffd928, init=<optimized out>, 
    fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffd918) at ../csu/libc-start.c:325
325	../csu/libc-start.c: No such file or directory.
(gdb) info break
Num     Type           Disp Enb Address            What
1       breakpoint     keep y   0x000000000040094d in main() at test.cpp:10
	breakpoint already hit 1 time
(gdb) delete break 1
(gdb) info break
No breakpoints or watchpoints.
(gdb) q
A debugging session is active.

	Inferior 1 [process 31780] will be killed.

Quit anyway? (y or n) y