python print trace for lines in execution

python:

# be careful with the output, it will flush your screen 😉
python -m trace --trace yourscript.py

gdb support in vim

pyclewn/:

# debug current buffer with pdb
:Pyclewn pdb %:p

having separate debug file for your executable when coredump

bash:

# we want to release a executable without debug symbols, when it coredump, we still
# want to be able to have informations such as function names, line numbers.
# make sure you compile your program as release, but with -g to keep debug symbols
# keep a debug copy of the executable
objcopy --only-keep-debug program program.debug
# strip symbols so you can give it to customer
strip -g program
# when you load coredump in gdb with program, it will automatically load
# program.debug in the same directory where program is

valgrind can check memory leak in your program

valgrind:

# valgrind needs debug symbols to give you more information about errors
valgrind ./myprogram
# show-reachable will show memory not freed, but you have maintained pointers to these memory
valgrind --show-reachable=yes  ./myprogram

valgrind has been my best friend for many years now. It provides you more than memory checking. I keep the example simple, check the man page to find discover new world.

debug a running program by attaching gdb to the process

gdb:

# find out the process id of your running program
pgrep myprogram
# attach gdb to the process
gdb --pid process-id

load core dump with gdb

gdb:

# change ulimit to allow core dump to be saved to disk
ulimit -c unlimited
# run program
./program
segfault (coredumped)
# load with gdb
gdb ./program core
# now you are at the line where the program segfaulted, if the program has debug information, you can trace back to the line number

coredump is the term where a program seg-faulted, the os dumps program memory space to disk.

display source in gdb

gdb:

# display source code window in gdb
Ctrl+x a
# display source code in gdb default mode
list

gdb is the most popular debugger on Linux. I use it all the time and really can’t live without it.