I'm trying to test out this answer:
_dl_runtime_resolve -- When do the shared objects get loaded in to memory?
But when I try various ways to run essentially the same as gdb "LD_BIND_NOW=y binary",it fails.
How can I run my app with this flag on inside gdb?
Two choices. First:
env LD_BIND_NOW=y gdb binary
Or, run gdb binary and then inside gdb:
set env LD_BIND_NOW=y
run
The former will affect the gdb binary itself, which may or may not matter. The latter might not actually work :-)
Related
I'd like to define a command which does X under gdb-multiarch, but prints out a helpful message when run under normal gdb. How can my script determine which of the two its run under?
Why? When I start gdb-multiarch, I can bind to a qemu-arm session. When I try that in gdb, I get bizarre errors. It's easy to forget and run gdb (and not -multiarch), and I want to my bind-to-qemu tell me "This must be run under gdb-multiarch".
Your question presumes that there is some difference between gdb and gdb-multiarch, but there doesn't have be any such difference.
Presumably on the OS you are using the gdb and gdb-multiarch are configured differently, with gdb only supporting native architecture, while gdb-multiarch supports cross-architecture debugging.
Presumably what you actually want to detect is that the target-architecture you need (arm ?) is / isn't supported by the current binary.
In the bind-to-qemu user-defined function, you can try to set architecture arm.
If that errors out, the rest of bind-to-qemu should not execute.
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 want to make gdb rpm from gdb.spec file using rpmbuld which I can do without any problem but now in addition to that i want GDB to be complied with symbols so that when gdb is being attached to itself I should know the exact call flow and where exactly its failing.
Reason for doing this exercise is I am creating the application which will internally invoke gdb by calling gdb_init and going down failing with segmentation fault in gdb source code.
The easiest way to prevent stripping debug symbols
in rpm build is to add exit 0 at the end of %install.
The symbols are stripped by commands that are appended
to the %install scriptlet. Adding "exit 0" prevents the
commands from being run.
I don't know how you would to this with rpmbuild, but building gdb is really easy. Just get official source package, unpack it, then configure this way:
CFLAGS="-g3 -O0" path/to/gdb/source/configure --prefix path/to/your/installation/directory
make
make install
O0 is not strictly necessary, but if you want to debug a gdb crash, it will help.
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 trying to debug a CUDA program, but when I'm launching gdb like so:
$ gdb -i=mi <program name>
$ r <program arguments>
I'm getting:
/home/wvxvw/Projects/cuda/exercise-1-udacity/cs344/HW2/hw:
error while loading shared libraries: libcudart.so.5.0:
cannot open shared object file: No such file or directory
Process gdb-inferior killed
(formatted for readability)
(I'm running gdb using M-xgdb) If that matters, then CUDA libraries are in the .bashrc
export PATH="/usr/local/cuda/bin:$PATH"
export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:/usr/local/cuda/lib64"
error while loading shared libraries: libcudart.so.5.0
This error has nothing to do with GDB: your executable, when run from inside GDB, can't find the library it needs.
export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:/usr/local/cuda/lib64"
GDB runs your program in a new $SHELL, so that should have worked. I wonder if there is some interaction with emacs.
In any case, this:
(gdb) set env LD_LIBRARY_PATH /usr/local/cuda/lib64
(gdb) run
should fix this problem.
Update:
as I've mentioned it before, ld path is set properly
No, it isn't. If it was, you wouldn't have the problem.
Now, I don't know why it isn't set properly. If you really want to find out, start by running GDB outside emacs (to exclude possible emacs interactions).
If the problem is still present, gdb show env, shell env, adding echo "Here" to your ~/.basrc, etc. should help you find where things are not working as you expect them.
I've had this problem as well. One way to look at it is that even if the LD_LIBRARY_PATH variable is correct when you enter show env into gdb, it may not be correct when you actually execute the program because gdb executes $SHELL -c <program> to run the program. Try this as a test, run $SHELL from the command line and then echo $LD_LIBRARY_PATH. Is it correct? If not, then you probably need to add it to your rc (.tcshrc in my case).
I had a similar problem when trying to run gdb on windows 7. I use MobaXterm to access a Linux toolbox. I installed gdb separately from http://www.gnu.org/software/gdb/ . I got it to work by making sure gdb could find the correct .dll files as mentioned by Employed Russian. If you have MobaXterm installed the .dll files should appear in your home directory in MobaXterm/slash/bin.
gdb however did not recognize the LD_LIBRARY_PATH variable. For me, it worked when I used the PATH variable instead:
(gdb) set env PATH C:\Users\Joshua\Documents\MobaXterm\slash\bin
(gdb) run
I would think using PATH instead of LD_LIBRARY_PATH might work for you provided you put the correct path to your library.
gdb is looking for a library, so why are you concerned with the include path? You may want to try to set the gdb option "solib-search-path" to point to the location of the libcudart.so.5.0 library.