I wrote a small program to modify the first packet’s timestamp in pcap file for test purpose; the code is simple and can be extended for changing other packets’ timestamps.
Month: July 2022
The gotcha of logging gdb output
By default, gdb‘s output file is appended, not overwrote. E.g: debug the same program for 2 times:
$ gdb foo
......
(gdb) set logging on
Copying output to gdb.txt.
Copying debug output to gdb.txt.
(gdb) r
......
$ ll gdb.txt
-rw-rw-r-- 1 nanxiao nanxiao 1067 Jul 9 18:06 gdb.txt
$ gdb foo
......
(gdb) set logging on
Copying output to gdb.txt.
Copying debug output to gdb.txt.
(gdb) r
......
$ ll gdb.txt
-rw-rw-r-- 1 nanxiao nanxiao 2134 Jul 9 18:08 gdb.txt
After second debug, the gdb.txt‘s size is doubled. To overwrite the output file, execute set logging overwrite on before set logging on:
$ gdb foo
......
(gdb) set logging overwrite on
(gdb) set logging on
Copying output to gdb.txt.
Copying debug output to gdb.txt.
(gdb) r
......
$ ll gdb.txt
-rw-rw-r-- 1 nanxiao nanxiao 1067 Jul 9 18:10 gdb.txtA trick of setting breakpoint in pdb
When using pdb to debug a python program:
python -m pdb foo.py
I want to set a breakpoint, but meet following error:
(Pdb) b bar.py:46
*** 'bar.py' not found from sys.path
A small trick is setting breakpoint in main first and run the program:
(Pdb) b main
Breakpoint 1 at ......
(Pdb) r
......
After breakpoint set for main is hit, set breakpoint again at bar.py:46. This time it should work:
(Pdb) b bar.py:46
Breakpoint 2 at ......