I need to set breakpoints in a cpp source file. The current setup to call the cpp target is through a shell target, with additional dependencies, which means it's not feasible to directly invoke the cpp target in Linux console.
As I searched online, there are generally two ways:
invoke gdb in shell
pause in cpp, let gdb connect to the process
I don't know how to do the first way, so I choose the second way here.
I insert sleep(30) in cpp file, then in another terminal I open gdb and connect to the running process. I confirm the gdb can stop at the sleep() function in gdb. But the problem is the gdb seems only knowing the sleep function context, without knowing the call site of the sleep function. If I force setting breakpoint in the main program, gdb shows no such file. If I continue in gdb, it will not stop at any breakpoints I set in cpp file.
You need to compile the program with debug symbols. Otherwise GDB will only know of symbols in the dynamic symbol table. Turning off optimizations also helps debugging. So add the flags -O0 -g.
If this is not possible, you'll have have to step through the disassembly (Ctrl+X, 2).
Related
I am new to Linux space.
My project creates 'so' (akin to our dll's) which is used by an executable.
Currently to debug, I invoke gdb -tui Which puts me into the gdb terminal where I put break points and do the r with parameters ... and debug.
Everything was fine, until now where the entire architecture has been changed.
Now to run our code, we execute a command
$ java -jar ... and a lot many parameters.
The jar files etc do not belong to us.
I am yet to find out what executable is called, or the code flow.
Question :
Is there a way to invoke gdb command from within my source code ?
say
MyClass::myFunc()
{
some calls
<THE GDB COMMAND>
What I am looking at is, once I place my 'so' in the path and execute the said java command, the gdb is invoked the moment it hits my function.
The solution provided here wasn't clear.
Invoke and control GDB from c++
I wrote a simple C++ program that requires some input to run. In the terminal I simply run in ./myProgram < fileWithData.txt. However I could not figure out how to specify and input file for the target executed in Xcode. I used the command line project. Of course I could use a different target, for example run Terminal.app and then pass it the executable with the input file but then I can no longer debug it.
This question: Cannot get lldb to read file input explains how to set the input path in lldb, but I could not find a way to specify lldb commands that are executed before the process is started.
I don't think there's a way to do this entirely from within Xcode. However if you set the Run Scheme in Xcode to the launch mode "Wait for executable to be launched," hit run, and then run your program from Terminal.app with the appropriate piping, the Xcode-embedded lldb will connect to it.
I'm using gcc 4.9.2 & gdb 7.2 in Solaris 10 on sparc. The following was tested after compiling/linking with -g, -ggdb, and -ggdb3.
When I attach to a process:
~ gdb
/snip/
(gdb) attach pid_goes_here
... it is not loading symbolic information. I started with netbeans which starts gdb without specifying the executable name until after the attach occurs, but I've eliminated netbeans as the cause.
I can force it to load the symbol table under netbeans if I do one of the following:
Attach to the process, then in the debugger console do one of the following:
(gdb) detach
(gdb) file /path/to/file
(gdb) attach the_pid_goes_here
or
(gdb) file /path/to/file
(gdb) sharedlibrary .
I want to know if there's a more automatic way I can force this behavior. So far googling has turned up zilch.
I want to know if there's a more automatic way I can force this behavior.
It looks like a bug.
Are you sure that the main executable symbols are loaded? This bug says that attach pid without giving the binary doesn't work on Solaris at all.
In any case, it's supposed to work automatically, so your best bet to make it work better is probably to file a bug, and wait for it to be fixed (or send a patch to fix it yourself :-)
I am using gdb to debug NS-2 which is a simulator for network protocols. It takes an .tcl file as input and interpret it. [I think it is an interpreter.]
Some of the code is written in tcl (events and creation of network components) and some in C++ (especially Packet Formats, Agents etc.).
I have created an Agent in C++ and i want to stop it at some function call so that i can see the stack trace and find which other classes have been called before it.
This is what i have done:
There was some error in one of my MyAgent::function and it was giving Segmentation Fault and gdb was stopping there automatically. I could then see the stack trace. I rectified the error.
Now when i run
gdb ./ns
b MyAgent::function()
/*
When i press TAB after writing "b MyA" it gives me all functions
of my class :). when i press enter after above command --
it asks me "Breakpoint on future shared library load" and i say Yes.
I hope this is ok ??
*/
r myfiles/myWireless.tcl
Now it runs and do not stop anywhere. :(
I am sure that this function is being called, because when that Segmentation fault was occuring, it was stopping at that function.
Thanks
You can add a breakpoint in that function:
(gdb) break MyAgent::function()
You must make sure to compile with whatever options are necessary to get debug symbols. On GCC, use the -g or -ggdb options.
You need the -args option to specify the tcl script that will be executed.
Run gdb like this:
gdb -args ./ns path/to/tcl/script.tcl
To enable debug flag to c++ code, if have not done it already, re-configure your ns2 instalation with:
./configure --enable-debug ;# plus any other flags you use for configuring
make clean
make -j 3 ;# -j for faster compiling
make install ;# optional
You can also use the --with-tcldebug=..., for debugging tcl code (You need to install tcldebug first for this option)
I'm doing an OS class that's based on xv6 and I wrote a program that needs to run on it.
I know that I can debug kernel code with make qemu-gdb but I'm not sure how to debug my own user program.
Lets say I want to debug cat, how would I go about doing that?
Thanks
P.S. isn't there an xv6 tag? should this question even go here?
From the xv6 top-level dir:
Run the emulator in debug mode (assuming no X11): make qemu-nox-gdb
In other terminal just run the debugger loading the kernel symbols with:
gdb kernel This is important, otherwise the debugger will be confused between kernel and and user program symbols, for example main()
From the gdb interface run: (gdb) target remote localhost:26000
where 26000 is the TCP port that the step #1 report at the end (this might change).
Load the user exec with (gdb)file user_program
Place a breakpoint (gdb) break main and continue with (gdb) continue
etc...
file cat, break main, continue
semi reference running and debugging xv6