During investigation of a hard fault I wished I could jump back to the line in the editor where I was before I hit [step]/[stepOver]/[go].
Background
A hard fault is some kind of interrupt service vector which is triggered by e.g. an invalid command. This clears all my registers and jump addresses where I came from. Great isn't it?
Result: "I kind of know which line I was, but precise? ok, again, be more careful the next time..."
TRACE32 stores the register values of the last 256 (by default) halts. You can go back with command Frame.UNDO (and forward with Frame.REDO). It is also possible to show the stored halts like a trace using the ART command group (Advanced Register Trace).
Related
When I put a "pause" command into my program, I can precede it with a disp("Just finished averaging") or something of the kind, so I can read on the console which "pause" I am at.
But when I lose my patience with a program that's taking forever to complete, and hit Ctrl-C to see what is going on, I cannot see a way of finding out which code line I interrupted it at. The "whereami" command tells me I am in pause, which is obviously true but hardly helpful; it's like a GPS device telling me I'm in the driver seat. Oh yeah, I figured that myself, thank you Captain.
I am tempted to create a dedicated variable, say MyApproximateCurrentCodeLine, and updating it every few lines of code with hard-wired substitution commands. This would work but would take a lot of time to write, a similar amount of time to remove when I'm done, and would have to be repeated with every program I need to debug. Not to mention it's just plain ugly.
Is there a better way of finding the current execution point?
Once you have interrupted the program
[linenum, callername] = where()
will give you the full calling tree.
S.
I want to press a key at any point, causing the simulation to stop without loosing data collected until that point. I don't know how to do the exit command. Can you give me some examples?
I think, WandMaker's comment tells only half of the story.
First, there is no general rule, that Control-C will interrupt your program (see the for instance here), but assume that this works in your case (since it will work in many cases):
If I understand you write, you want to somehow "process" the data collected up to this point. This means that you need to intercept the effect of Control-C (which, IF it works as expected, will make the controlling shell deliver a SIGINT), or that you need to interecept the "exit" (since the default behaviour upon receiving a SIGINT would be to exit the program).
If you want to go along the first path, you need to catch the Interrupt exception; see for example here.
If you want to follow the second route, you need to install an exit handler. Note that it will be called too when the program is exited in the normal way.
If you are unsure, which way is better - and I see no general way to recommend one over the other -, try the first one. There is less chance that you will accidentally ruin something.
This is my first question in Stack Overflow, since up until now, I always managed to find my answers.
So.. I'm writing a debbuger (for Windows, in python, using WinAppDbg library) that should trace the program execution, and encountered some problems.
I'm setting the trap flag, so I could stop every single step.
First problem - sometimes the execution flow goes through a Windows api, which goes to the kernel. When it returns, obviously the trap flag is off, and the execution of the thread may continue millions of instructions without my debbuger tracing every step of it.
Chance of solution - before a Windows api is called, I set the next addresses permissions as guard page, thus when the call returns, I get a guard page exception, setting the trap flag again, and continue tracing. But this cause a different problem (I call it "second problem")
Second problem - since I'm setting the trap flag of my main thread, all I see is a loop of that thread (I guess it's the Windows gui loop), and the program execution isn't advancing (for example, there should be new threads created, but I don't see them).
So what am I looking for?
A debugger's source code that can handle the problems I've described.
Or better yet, a solution to my problems. What am I doing wrong?
Thank you all!
I rarely used the netbeans debugger but I have this bug in my program which I'm trying to get to the bottom of. Basically my program searches a binary file (4.5gb) for a seqeunce of bytes and writes it to file. However, the programm always stalls at this specific point in the file when reading near halfway of the file (~2gb). They way I using the debugger if putting a breakpoint and keep "continuing" the debugger until it reaches that point in the file but it's going to take forever to reach the 2gb mark. I'm guessing there's a better way to use the debugger which I'm not aware of. Any suggestions?
Netbeans supports conditional breakpoints. If you add a breakpoint via the menu "Debug / New Breakpoint" (or just hit Ctrl+Shift+F8) you can specify a condition (either how often the breakpoint has to be hit until it execution is halted on this breakpoint or an expression).
You could keep a count of how much data you have processed, and add an if() block which checks whether you are up to the 2GB mark. Put a dummy command inside the if() block, and add a breakpoint on the dummy command; this will only be reached when you have processed sufficient data.
I'm trying to watch the execution of a VB6 app and I'm running into an issue because once I enter the debugger and then hit Continue, it no longer lets me step through the code until I hit another break point. I want to be able to execute a program without stepping through something until I hit a point where I want to watch it execute. Ideally this would be something to the effect of holding a key down while I pressed a button to 'step into' that function.
Thanks in advance!
[EDIT]: I'm aware that I can use break points to stop the execution. To be more clear, the problem is that I don't know where the execution is going to, so I can't set the break point there (because I don't know where there is). That's why I essentially want to be able to say, 'after this next thing that I do, break, no matter what'. It sounds like this functionality does not exist, but I'm still keeping my fingers crossed.
While the code is running, press ctrl+break (or the 'VCR pause' button in the IDE) then press F8 (or choose 'Step Into'from the Debug menu in the IDE) to continue running the app. The next action will cause execution to break.
Note that the which causes the break will not always be the one you hoped it would be. Particularly annoying is the _MouseOver event which prevents you from doing a mouse down or a timer firing quckier than you can perform your action. Some breaks may even be fatal as regards running your app e.g. where Windows messages have been hooked (subclassing). Also consider there may not be an event handler in code (yet) for your action where it can break. But usually this technique identifies where you should be setting your breakpoint.
There is a Stop statement available for use in VB6 that will drop to the debugger when the statement is executed from code running through the IDE. (Just be sure to remove the all of the Stop statements from the code when compiling a release build.)
There are several techniques you can use.
These two have been mentioned
Using F8 and Shift-F8 to step through the program
Adding Stops (and later removing)
Others
Use a global variable to create a collection. Use it as a stack and have the subroutines you are interested in push and and pop strings. Conversely don't pop anything and you will get a trace.
Use Watches to monitor and break at selection conditions. You can setup just about any condition to break.
Make a Global String and have your procedures set when you enter them. Monitor it through a Watch.
Use Debug.Print in your code. Also Unlike Stop you can leave these in without effecting the production code.
Use the File System Object to create a text file to act as a log.
Sometimes problem only occurs in the Complied version then you need to use MsgBox or log to a text file. MsgBox can alter the behavior of complex user interactions with forms.
These are all techniques I used in debugging an application. If I had to monitor an application I would use Debug.Print. If that doesn't do the trick compile then log to a text file.
If you have something really complex going on then I recommend moving all your code out of the events into classes implementing a Command Pattern. Your commands classes should interact with the form through and interface.
In the Execute method of the command classes you will something like
<save the current state>
<Do your original code>
<save the modified state>
<push the command onto a stack>
What will happen is that you wind up with a list of all the commands you have executed (even things like mouseover) with the state they encountered and the modified state. You can then examine each object in turn to see what is happening. This is nearly the equivalent of creating Undo/Redo
Note however things like MouseOver can push a lot of classes on the command stack so you will have to structure your tests carefully or be overloaded with information. Remember you can always skip pushing the command onto the stack.
The downside of using commands is that you gone beyond debugging into redesigning. You will to decide whether the problem is worth doing this.
You can press the F8 key to step through the code line by line. Alternatively, you can press SHIFT-F8 to step through line by line.
F8 will step you in to a function, where SHIFT-F8 will step you over the function. If you click on the DEBUG menu in the VB IDE, you will see other options too.
EDIT:
You can also put a permanent break point in your code by using:
Debug.Assert False
By doing it this way, the 'breakpoint' is saved in your code. When you compile the app, debug code is ignored.