I have a program that is seg faulting and I reproduce in gdb as follows:
$ gdb myprogram
(gdb) run mycmdlineargs
Program received signal SIGSEGV, Segmentation fault.
If I type:
(gdb) list
it shows me the source code line where the seg fault occurs, but I would like to see the disassembly (preferably annotated with source code). What command can I use to do that?
You want the disassemble command.
Related
I have a C-and-C++-based project I just got to build and link for the first time, and it segfaults on execution. I tried running it in gdb to get a backtrace, and saw this:
gdb) run
Starting program: /home/jon/controlix-code/bin/controlix
During startup program terminated with signal SIGSEGV, Segmentation fault.
(gdb) bt
No stack.
(gdb)
I assume it is crashing before main() is called, but beyond that I don't have a clue. I haven't been able to find much about this type of situation on Google, so I thought I'd ask here.
One approach is to catch all exceptions before running:
catch throw
run
And if that does not help, you may have to single-step through the assembly from the very beginning. But before you do that,
break main
run
and single-step through the code using step and next should lead you to the culprit.
I am using the g++ compiler to compile my code, and I am reaching a Segmentation Fault after the main method returns. I am unable to get what is causing the fault as GDB returns each frame on the stack in the form: #0 0x00007ffff7007478 in ?? ().
The frame #5 is 0x0000000000000000 in ?? () and I find it interesting that it's at address 0, does that mean anything in particular?
I have updated GDB and my g++ compile flags are: -std=c++11 -g -ggdb -O0
Any ideas? If you need anything more, let me know. Thanks!
0x0000000000000000 in ?? () is likely caused from dereferencing a null pointer.
You have the correct debugging flags enabled, but you aren't looking at the call stack.
Try running the program again through gdb, allow it to crash, and then run bt.
This will give you a back trace. You will be able to find the last described function where the problem was likely to have occurred.
My program is crashing some where, i tried to debug using GDB. when i use back-trace, it's just showing first line address
I compiled it by -g option. How would i find,where the exact core dump is happening.
I'm getting this:
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7580d75 in ?? () from /lib/x86_64-linux-gnu/libc.so.6
Can I know why the seg fault is occuring?
I am currently printing the content of a C++ map in a file when this error occurs. The map size would be in MBs, could that be a problem?
Try installing debugging symbols for libc, they should be available as a package. In ubuntu they can be found in the package libc-dbg. Gdb should produce better output for you then.
I have this output when trying to debug
Program received signal SIGSEGV, Segmentation fault 0x43989029 in
std::string::compare (this=0x88fd430, __str=#0xbfff9060) at
/home/devsw/tmp/objdir/i686-pc-linux-gnu/libstdc++-v3/include/bits/char_traits.h:253
253 { return memcmp(__s1, __s2, __n); }
Current language: auto; currently c++
Using valgrind I getting this output
==12485== Process terminating with default action of signal 11 (SIGSEGV)
==12485== Bad permissions for mapped region at address 0x0
==12485== at 0x1: (within path_to_my_executable_file/executable_file)
You don't need to use Valgrind, in fact you want to use the GNU DeBugger (GDB).
If you run the application via gdb (gdb path_to_my_executable_file/executable_file) and you've compiled the application with debugging enabled (-g or -ggdb for GNU C/C++ compilers), you can start the application (via run command at the gdb prompt) and once you arrive at the SegFault, do a backtrace (bt) to see what part of your program called std::string::compare which died.
Example (C):
mctaylor#mpc:~/stackoverflow$ gcc -ggdb crash.c -o crash
mctaylor#mpc:~/stackoverflow$ gdb -q ./crash
(gdb) run
Starting program: /home/mctaylor/stackoverflow/crash
Program received signal SIGSEGV, Segmentation fault.
0x00007f78521bdeb1 in memcpy () from /lib/libc.so.6
(gdb) bt
#0 0x00007f78521bdeb1 in memcpy () from /lib/libc.so.6
#1 0x00000000004004ef in main (argc=1, argv=0x7fff3ef4d848) at crash.c:5
(gdb)
So the error I'm interested in is located on crash.c line 5.
Good luck.
Just run the app in the debugger. At one point it will die and you will have a stack trace with the information you want.