On 3/4/2012 11:50 PM, Chad J wrote:
Problems: - I have to rerun the program in a debugger to see the stack trace. This is a slow workflow. It's a big improvement if the segfault is hard to find, but only a small improvement if the segfault is easy to find. Very bad if I'm prototyping experimental code and I have a bunch to go through.
I don't get this at all. I find it trivial to run the program with a debugger: gdb foo >run that's it.
- It only gives one line number. I imagine there's a way to get it to spill the rest? At least it's the most important line number. Nonetheless, I commonly encounter cases where the real action is happening a few levels into the stack, which means I want to see ALL the line numbers /at one time/.
That's because the runtime library is compiled without debug symbols in it. If it was compiled with -g, the line numbers would be there. You of course can compile the library that way if you want. Debug symbols substantially increase your program size.
- As I mentioned in another post, it is unreasonable to expect others to run your programs in a debugger. I like it when my users can send me stacktraces. (And they need to have ALL the line numbers displayed with no extra coercion.) There are a number of occasions where I don't even need to ask how to reproduce the bug, because I can just tell by looking at the trace. Super useful!
I agree that customers emailing you a stack trace is a reasonable point. Andrei also brought up the point of the problems with using a debugger on a remote server machine.
I wouldn't even expect ALL hardware errors to be instrumented in the compiler. At least get the common ones. Null dereference is remarkably common. I can't actually think of others I care about right now. Array boundary errors and assertions already seem to have their own exceptions now; they were great pests back in the day when this was not so.
No hardware support for them, so no choice.
The error messages could use a lot of work though. (Range Violation should print the index used and the index boundaries, and simpler assertions such as equality should print the values of their operands.)
The added bloat for this would be substantial.
I'm pretty sure other languages like C# and Java get this right. Haven't used those two in a while though. Haxe... totally got this right. Also Actionscript 3 by proxy. Hell, even Synergy/DE, the DIBOL (!!) derivative that I use at work, /gets this right/. I get stacktraces for null dereferences in these languages. It's /really/ convenient and useful. I consider D to be very backwards in this regard.
Notably, C and C++ do not do what you suggest.
