I want to debug an application with lldb. At the beginning, I want to set a few breakpoints with a set of commands. I'm aware of the -s option, but this somehow doesn't let me interactively debug the application after executing the commands in the file. Essentially I want to replicate the behavior of gdb. How do I do this?
There is a bug in the way the lldb command parser sources command files, where it doesn't recognize that a command like "breakpoint command add" has switched to a new "input parser" (the one that reads and stashes away the commands but doesn't execute them, and then waits for the DONE to exit.) The effect of this is that, if you do:
breakpoint command add
some command
some other command
DONE
the input gets all messed up and things go poorly, as you have seen. This bug is actually fixed in TOT lldb, though that hasn't made it to an official Xcode release yet.
In the meantime, there aren't any great workarounds for this. If your breakpoint commands are simple, you can use the --one-liner option to specify them without switching to the breakpoint input parser. Or, if you know a little Python you can make Python function breakpoint commands, import them with "script import" and tie them to the breakpoint with the -F option.
Related
I am learning C Programming currently on VS Code. I run program a lot of time repeatedly which mess up terminal. Mostly I use cls before running program to clear previous output of terminal. My default terminal is PowerShell in VS Code. Is there any way to clean terminal before each run.
What I have tried after google search:
-I have tried adding cls to powershell profile but it does not work on every code run.
-Checking clear previous output in coderunner settings didn't work either.
The easiest way is to add cls to the beginning of your code, but that's not always best:
You can also set a keyboard shortcut for clearing the console (Used to be ctrl+k, but was removed)
You don't want to replace the existing behavior when running code, but a pretty simple one-button solution could be setting up a vs code macro to do Terminal: Clear, and also run your open file in the terminal.
I would like to set multiple breakpoints at once in different files in GDB.
Is it possible to have a script or any other way which I can run once I enter GDB debugger and have all the breakpoints set instead of setting them one by one using traditional set break command.
All the resources I searched pointed to how to set breakpoints effectively. But, nothing seems to address my concern.
You can use the source command in gdb.
You can also put the commands in the .gdbinit file which will be sourced when you start gdb. Put the commands there and they will be run without doing anything more.
I'm trying to debug for the first time a gtk code and actually, I want to debug a callback function for key-press-event so I set a breakpoint with gdb and when it hits the breakpoint, the whole desktop evirement is freezing (I'm running under gnome-shell) it seems that the graphic envirement is waiting for the event to finish.
I got some idea that didn't worked :
The first attempts was to assign some gdb commands to the breakpoint :
(gdb) break on_key_press_callback
(gdb) commands
> back trace
> next
> next
> next
> continue
> end
but I don't know why, only the back trace command is executed, and then freeze.
The second attempt was to debug remotely using gdbserver and gdb on tty1 (no graphigs to freeze :) ) I was able to send commands like next and step after the breakpoint but there was nothing to see (can't list code, inspect the stack, ect ...)
So any good tips to be able to debug in such situations ?
Thanks
It's typical to have lockups when debugging an X program running on the same server that you're using to debug. For example, if the inferior (gdb terminology for the program being debugged) does a server grab -- whoops, the gdb GUI (or terminal or emacs etc) is locked out.
Your idea of doing more programmatic debugging is a good one, but it's hard to make it all work nicely. As you found, some gdb commands (basically those related to inferior control) don't work in commands. Also, it just isn't nearly as convenient.
You can go further that direction. For example you could use SystemTap to probe the program instead.
However there are also nicer approaches.
One way is to run the inferior using a virtual X server -- a nested one, or one running in a VM. Then you can escape to the "outer" X server for debugging. This will be much nicer.
Another way is to have two computers, and run the debugger on one and the inferior on the other. In a way this is really the same answer, just using a real machine rather than a virtual one.
The question is old, but for anyone that may be struggling with this issue, there is a way to stop the freezing behaviour from happening by disabling the X server grab.
You have to change the config in your IDE to run the program with the following system property:
-Dsun.awt.disablegrab=true
If you are using javaws (Java Web Start) to run the application use:
-J-Dsun.awt.disablegrab=true
instead.
For years now my Windows C tagging/scoping solution has almost worked. I can build the filelist, build the tags (via Exuberant Ctags) for vim/gvim navigation, build cscope.out, and tag around within gvim.exe windows I launch by clicking on C source files.
The final piece that eludes me is that I can't seem to get cscope in cmd.exe to launch my editor when I select an item. I made sure gvim.exe is in my Path environment variable. I made sure the CSCOPE_EDITOR environment variable is set (more on that below). But when I select a line item from within cscope the editor is not launched. Instead I get one of the two following failures:
If CSCOPE_EDITOR is either gvim.exe -f or "gvim.exe -f" then I see that printed at the top of the cmd.exe window followed by the line offset and the filename (e.g. "gvim.exe -f +72 myfile.c") and then it quickly returns to cscope without the editor ever popping.
If CSCOPE_EDITOR is gvim.exe (without the -f option) then a gvim.exe process is kicked off (I see it in Windows Task Manager under Processes) but it never comes to the foreground as an application. Furthermore, the cscope window in cmd.exe goes blank and is unresponsive until I manually kill the gvim.exe process that was spawned.
For reference:
cscope -V returns "cscope: version 15.8a" and was downloaded from this site: http://code.google.com/p/cscope-win32/
My version of gvim.exe is 7.3 which the latest available from http://www.vim.org/
Also, I have tagged this post with "C" because, while this is not a C language question, cscope and ctags are primarily used for C programming and thus I think the C tag is relevant. (Thought I'd point that out before someone comes along and removes the tag and says this isn't a C question, since C programmers are the most likely people to have the answer.)
With help from #mattn and #mMontu and a lot of trial-and-error and an ugly but simple hack I finally have this working. Here are the problems I encountered:
cscope-win32 does not handle spaces in the EDITOR or CSCOPE_EDITOR environment variables. I tried every space-escape trick I could think of (single-quotes, double-quotes, backslash escapes) and nothing worked.
When gvim.exe is successfully launched by cscope-win32, if that gvim.exe tries to add the same cscope.out database (via cs add cscope.out) the add command hangs. If the add is part of a vimrc file then the editor will hang during opening (with the gvim.exe and cscope.exe processes starting but the application window never appearing). If the add is done after the editor window opens then the window will hang. This appears related to multiple cscope-win32 processes being attempted in the same process tree, but I have no actual proof of that.
Here's my solution to the problem. Like I said, it is an ugly but simple hack.
Create a wrapper batch file. I named mine gvim_cscope.bat. Make sure it is in a directory that exists in your PATH environment variable. You can verify this in a cmd.exe shell by calling "where gvim_cscope.bat".
Edit the batch file and add your editor command but precede it with the windows start command. For example, my batch file contains the following:
start gvim.exe %*
Create/Update your CSCOPE_EDITOR environment variable to be "gvim_cscope.bat". In case you've never modified a Windows environment variable before, you can get to them (on Windows 7 anyway) via Start -> right-click Computer -> Properties -> Advanced System Settings -> Environment Variables.
That's all I needed to get things working. Open a new cmd.exe window (so the updated environment variable is pulled in) and open cscope.exe and everything works. I am able to pop multiple gvim.exe windows from within cscope.exe, each with its own connection to the cscope.out database. The first problem is avoided by using the wrapper batch file (no more spaces in the command) and the second problem is avoided by using the windows start command so that gvim.exe is started as a separate process.
Thanks for the help #mattn and #mMontu. So nice to have things working right!
How to make an application to prevent itself from launching from the command line?
I have a binary which should be launched by a daemon; but when somebody tries to launch the binary from command line, I should error out stating "cannot be launched from command line".
Tried googling but in vain.
PS. http://www.daniweb.com/software-development/c/threads/449682/stop-launching-from-command-line
I wanted to check if there are better ways than those mentioned in the link..
I am not sure there is a bullet proof answer (to how to prevent a program to be started from command line). You could consider
testing with isatty(3) that STDIN_FILENO (i.e. 0) is not a tty
try to open /dev/tty (it should fail) see tty(4)
testing with getsid(2) that your are not in the same session than your parent, or starting a new session with setsid(2)
calling yourself daemon(3)
And I am not sure that you always want to reject being started from a terminal. For debugging, you surely want to be able to be started from a terminal. I actually would just warn, not quit, if started from a terminal.
And you probably want to install your program outside of standard paths, maybe in some libexec/ or sbin/ directory.
See also capabilities(7), pty(7), termios(3)
For the record, testing with isatty(3) only works if you are writing that binary files yourself. The method would fail if you are trying to prevent people from starting a third-party binary files.
Generally speaking, to prevent people from starting the specific program(s) from command line, the *nix way is to chown the binary file(s) to be owned by the daemon that launches it, and also to be of owned by the group say no_command_line. Then chmod 705 binary_executables, and put all those people not allowed to run the binary_executables from command line in the group no_command_line.
HTH