Insure++

In order to combat the “creative user” problem, there is a type of program which will take source code or object files and produce a version that analyzes itself for bugs as it runs.
An Example

Figure 1. Insra Window Showing Errors

Figure 2. Stack Trace at Memory Leak Location

By now, I felt I knew enough about Insure++ to do an example for this review. I selected a printed circuit layout program called pcb-1.3 in the apps/circuits directory of sunsite.unc.edu. (There is a newer version of pcb available.) This program consists of slightly over 600KB of source code, so it is a reasonably complex program, even though it is by no means huge. When compiling the program, Insure++ warned about several possible problems, but none of them looked too serious. I then started up pcb using the example data that came with it. I had no idea how to use the pcb software, so I just started clicking on things. (This is usually an excellent way to find bugs.) After a few minutes of playing with the program, I had six memory leaks and one NULL pointer evaluation listed in the Insra window (see Figure 1). At this point, I clicked on the error for line 1352 of the program action.c, and the screen shown in Figure 2 popped up. This shows the stack trace when the memory was allocated and when it was leaked. If you click on the red arrows, the indicated source code will be opened in your favorite editor. A quick look at the source code shows why Insure++ is complaining. In the function ActionSave on line 1290 of action.c, the program gets a file name from the user:

1289 case F_LayoutAs:
1290  name = GetUserInput("enter filename:", "");
1291  if (name)
1292  SavePCB(name);
1293  break;

This file name is contained in memory set by malloc, pointed to by the variable name, a local variable in ActionSave. Later, at line 1352, we leave ActionSave:

1349  break;
1350  }
1351 }
1352 }
There is no code in ActionSave to free the memory pointed to by name. When we leave the function ActionSave and the local variable name ceases to exist, there is no way to access this memory anymore—it has been leaked. Insure++ is warning us about this situation.

In addition to several memory leaks, Insure++ found a bug in the program related to using NULL pointers. It complained about this line:

469 return(&LineSortedByHighX[Layer][index2]);

I couldn't see anything wrong with this line by looking at it, so I restarted the program in the debugger, using the _Insure_trap_error breakpoint I mentioned earlier. When the program stopped, I examined the expression and it turns out that LineSortedByHighX[Layer] is NULL. The reason the program does not crash on this line is that we are taking the address of LineSortedByHighX[Layer][index2] rather than trying to dereference it. Presumably, at some later time, some function will evaluate this address and crash. Insure++ makes it possible to fix the problem and prevent a crash.

Conclusion

As you might be able to tell, I think Insure++ is a great product. It finds programming errors better than any other product I have used, it runs under my favorite operating system, and Parasoft's technical support is excellent. There is one problem—it's expensive. The cheapest configuration you can buy is a 3-user-node locked license, which costs $1,995 per node. Nothing I do on my home computer is worth that much money, so I won't be buying a copy of Insure++ for myself. I suspect that most people who program for fun will not be buying a copy either. Who should buy Insure++ then? People, or more likely companies, who do professional software development. When you are paying programmers several thousand dollars a month and bugs cost big money to deal with, then the price begins to look more attractive. When you consider that Insure++ might enable you to ship your product earlier, it begins to look very attractive. If you develop software for a living, you need this product. Insure++ runs under several flavors of UNIX and Windows too. In fact, anyone who is in an environment where programming time is money should consider evaluating Insure++. It is an excellent product.

Jim Nance (jlnance@avanticorp.com) works as a software engineer for the Verification Products Division of Avant! Corporation in Research Triangle Park, North Carolina. He has been using Linux since kernel version 0.12. In addition to hacking Linux, he enjoys reading murder mysteries, getting bossed around by his 3-year-old daughter, and spending time with his Sunday school class.

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