7.1 Statement level tracing

The ‘nana-trace’ executes a program and generates a message for each line of code executed (a statement trace). The statement level trace is useful for things such as:

• Understanding code.
• Measuring test coverage.
• Comparing runs of the code when regression testing, e.g. verifying that change X only changes the behaviour of program P for test case Z.

For example the ‘make ex-trace’ command in ‘gdb’ generates:

     % make ex-trace
     gcc -g test.c
     sh ./nana-trace a.out
     47           setbuf(stdout, NULL); /* disable buffering */
     49           printf("** main()\n");
     ** main()
     50           printf("** 1: %d\n", distance(1,-5));
     distance (i=1, j=-5) at test.c:43
     43           return abs(i - j);
     abs (i=6) at test.c:35
     35           if(i >= 0) {
     36                return i;
     40      }
     distance (i=1, j=-5) at test.c:44
     44      }
     ** 1: 6
     main () at test.c:51
     51           printf("** 2: %d\n", distance(twice(1),-5));
     twice (i=1) at test.c:29
     29           i = i * 2;
     31           return i ;
     32      }
     distance (i=2, j=-5) at test.c:43
     43           return abs(i - j);
     abs (i=7) at test.c:35
     35           if(i >= 0) {
     36                return i;
     40      }
     distance (i=2, j=-5) at test.c:44
     44      }
     ** 2: 7
     main () at test.c:52
     52           printf("** 3: %d\n", distance(3,-5));
     distance (i=3, j=-5) at test.c:43
     43           return abs(i - j);
     abs (i=8) at test.c:35
     35           if(i >= 0) {
     36                return i;
     40      }
     distance (i=3, j=-5) at test.c:44
     44      }
     ** 3: 8
     main () at test.c:53
     53      }