Gdb

Download here: http://gg.gg/wdc07
*Gdb (and Ddd) Guide - Swarthmore College
*GDB Tutorial: Essential GDB Tips To Learn Debugging
*Gdb Commands
There are types of bugs that are difficult to debug from within Python:
*segfaults (not uncaught Python exceptions)
*
hung processes (in cases where you can’t get a Python traceback or debug with pdb)
*out of control daemon processes
Sep 28, 2018 Miscellaneous gdb commands. L command: Use gdb command l or list to print the source code in the debug mode. Use l line-number to view a specific line number (or) l function to view a specific function. Bt: backtrack – Print backtrace of all stack frames, or innermost COUNT frames. Help – View help for a particular gdb topic — help TOPICNAME. Mar 22, 2009 gdbhas an interactive shell, much like the one you use as soon asyou log into the linux grace machines. It can recall history with thearrow keys, auto-complete words (most of the time) with the TABkey, and has other nice features.
In these cases, you can try gdb. Prerequisites
You need to have gdb on your system and Python debugging extensions. Extensions package includes debugging symbols and adds Python-specific commands into gdb. On a modern Linux system, you can easily install these with:
Fedora:
*
sudo yum install gdb python-debuginfoGdb (and Ddd) Guide - Swarthmore College
Ubuntu:
*
sudo apt-get install gdb python2.7-dbg
Centos*:
*
sudo yum install yum-utils
*
sudo debuginfo-install glibc
*
sudo yum install gdb python-debuginfo* tested on Centos 7. python-debuginfo is installable after the first two commands.
For gdb support on legacy systems, look at the end of this page. Running with `gdb`
There are two possible ways:
*
run python under gdb from the start. Note: the python executable needs to have debug symbols in it which may be another exe python2.7-dbg depending on your system
*attach to already running python process
To run python under gdb there are also two ways.
Interactive:
Automatic:
This will run the program til it exits, segfaults or you manually stop execution (using Ctrl+C).
If the process is already running, you can attach to it provided you know the process ID.
Attaching to a running process like this will cause it to stop. You can tell it to continue running with c command. Debugging process
If your program segfaulted, gdb will automatically pause the program, so you can switch into gdb console to inspect its state. You can also manually interrupt program execution by pressing Ctrl+C in the console.
See the page EasierPythonDebugging for the list of Python helper commands for gdb. Getting a C Stack Trace
If you are debugging a segfault, this is probably the first thing you want to do.
At the (gdb) prompt, just run the following command:
With luck, this will give some idea of where the problem is occurring and if it doesn’t help you fix the problem, it can help someone else track down the problem.
The quality of the results will depend greatly on the amount of debug information available. Getting a Python Stack Trace
If you have Python extensions installed, you can enter:
to get stack trace with familiar Python source code. Working With Hung Processes
If a process appears hung, it will either be waiting on something (a lock, IO, etc), or be in a busy loop somewhere. In either case, attaching to the process and getting a back trace can help.
If the process is in a busy loop, you may want to continue execution for a bit (using the cont command), then break (Ctrl+C) again and bring up a stack trace.
If the hang occurs in some thread, the following commands may be handy:
Current thread is marked with *. To see where it is in Python code, use py-list:
To see Python code positions for all threads, use: References
*
http://fedoraproject.org/wiki/Features/EasierPythonDebugging
*
https://github.com/spyder-ide/spyder/wiki/How-to-debug-Spyder-deadlock-freeze-hangGDB on Legacy systems
It may happen that you need to use gdb on a legacy system without advanced Python support. In this case you may find the following information useful. GDB Macros
A set of GDB macros are distributed with Python that aid in debugging the Python process. You can install them by adding the contents of Misc/gdbinit in the Python sources to ~/.gdbinit -- or copy it from Subversion. Be sure to use the correct version for your version of Python or some features will not work.
Note that the new GDB commands this file adds will only work correctly if debugging symbols are available.
Depending on how you’ve compiled Python, some calls may have had their frame pointers (i.e. $fp in GDB) optimised away, which means GDB won’t have access to local variables like co that can be inspected for Python callstack information. For example, if you compile using -g -O3 using GCC 4.1, then this occurs. Similarly, with gcc 4.5.2 on Ubuntu (at least) the macros fail for the same reason. The usual symptom is that you’ll see the call_function routine appearing to be between PyEval_EvalFrameEx and PyEval_EvalCodeEx, and the macro failing with No symbol ’co’ in current context.. There are two work-arounds for the issue:
*
Recompiling python with make ’CFLAGS=-g -fno-inline -fno-strict-aliasing’ solves this problem.
*
Patching the conditionals for Python frames in the pystack and pystackv routines to ignore frames with where $fp is 0, like so:
Also note that the stop condition for the while-loops in the pystack and pystackv routines were originally designed for the case where you’re running the Python interpreter directly, and not running the interpreter withing another program (by loading the shared library and manually bootstrapping the interpreter). So you may need to tweak the while-loops depending on the program you’re intending to debug. See, for example, this StackOverflow post for another (putative) stop condition. Getting Python Stack Traces With GDB MacrosGDB Tutorial: Essential GDB Tips To Learn Debugging
At the gdb prompt, you can get a Python stack trace: Gdb Commands
Alternatively, you can get a list of the Python locals along with each stack frame: More useful macros not in python’s gdbinit file
See http://web.archive.org/web/20070915134837/http://www.mashebali.com/?Python_GDB_macros:The_Macros for some more handy python gdb macros.
The graphical user interface (GUI) domainates the current operatingenvironments for personal computing. However, there are still tons ofpowerful tools, such as gcc and gdb, using the traditional text-basedinterface. Now, let’s turn on the terminal within Linux, FreeBSD, Mac OS X, or any other UNIX-like operating system to discover the power ofcommand-line tools!
*If you don’t have any linux machine available, please try to login ieng6.ucsd.edu and ieng9.ucsd.edu with ssh clients. If you have problemlogin these machines, please contact Hung-Wei.Contents
*gcc
*gdbgcc
gcc is the C and C++ compiler developed by GNU project. It is widelyadopted as the default compiler of UNIX-like systems. If you are using aMac, you may also get gcc by installing Xcode (Developer) Tools in the Mac OSX installation Disc #1. Basic Usage
Assume that we have a C source file ’garbage.c’ with the content of shown below:The basic way of compiling garbage.c into an executable file called ’garbage’ is:
*gcc -o garbage garbage.cIf the program is compiled without errors, you can execute the program bytyping ’./garbage’ followed by two numbers as its arguments.
If you are interested about how the assembly code of garbage.c look like, youcan also generate the assembly code by replacing the ’-o garbage’ option with’-S’ as: Bt download tool mac.
*gcc -S garbage.c The gcc will stop compiling the program after the ’garbage.s’ file isgenerated. You may use any text editor to browser the content of theassembly code. To figure out what the assembly code does, you may referencethe following documents. . . .
*A good document on x86 ISA. Frequently Used OptionsIn addition to the basic usage, gcc also provides options that help youoptimize or debug your code. For example, you may:
*Compile your code with debugging information:
*gcc -g -o garbage garbage.c
*Compile your code with optimizations:
*gcc -On -o garbage garbage.c Notice: n is usually a number through 1 to 3. The larger the number, the more optimizations are performed while compiling the code. The optimization options may differ in each platform. For example, the gcc under Mac OS also supports -Os and -Oz to allow optimization for code size.
*For other optimization/debug options, you may use
*man gcc under any UNIX-like system. gdb
gcc is a debugger by GNU project. Gdb can step through your sourcecode line-by-line or even instruction by instruction. You may also watchthe value of any variable at run-time. In additon, it also helps to identifythe place and the reason making the program crash. Basic Usage
All program to be debugged in gdb must be compiled by gcc with the option’-g’ turning on. Continue with the ’garbage’ example, if we want to debug theprogram ’garbage’, we can simply start gdb by:
*gdb ./garbageThen, you will see the gdb environment similar as following:
To start running and debugging the program, we can simply type the ’run’command after the (gdb) prompt as below: If the program takes arguments such as ’garbage arg_1 arg_2’, we may start running the program with these arguments as:Breaking ProgramTo inspect the current state of program exeution, we need to break theexecution of debugging program in gdb. At any point, we may use ctrl-c to interrupt the running program. However, ctrl-c is hard tohelp breaking our program at a specific point. Therefore, gdb provides the ’breakpoint’ function that allows us to break debugging program at the’breakpoint’ set by ourselves. Gdb allows the breakpoint to be set to anysource code line, function, or even any instruction.
*Break by line: to break the program at the beginning of a certainline, we can use the command ’break source_filename:line_number’.For example, if we want to break at the beginning of main function ingarbage.c, we can do as below:
*Break by function: to break the program at the beginning of a certainfunction, we can use the command ’break source_filename:function_name()’.For example, if we want to break at the beginning of main function ingarbage.c, we can also try below:
*Break by instruction: to break the program at the beginning of a certainmachine instruction, we can use the command ’break *PC’. For example, if we want to break at the beginning of main function in garbage.c, we can also try below:
To show the current breakpoints we have, we may use the ’info breakpoint’command as:
To disable a breakpoint we have, we may use the ’disable breakpoint_number’.To re-enable disabled breakpoint, we can turn it on by ’enablebreakpoint_number’. To remove a breakpoint, we can use ’deletebreakpoint_number’ or replace the ’break’ with ’clear’ command as wecreate these breakpoints.
To resume the exeution of the interrupted program, we can use the ’continue’or ’c’ command. Stepping through programOnce a running program is interrupted in gdb, we can step the program toinspect how the program is executed. Gdb provides several stepcommands to allow stepping program with different granularities:
*s: the debugger will step to the next line in the source code.For example, using the s command, the program will step through line 9 from line 8 after the program interrupted by breakpoint 1.
*si: the debugger will step to the next instruction in the compiled code. For example, using the si command, the program will stepthrough PC 0x00001f91 from 0x00001f8e.
*n: the debugger will step to the next source line. Each function callwill be treat as a single source code line. Inspect variables/register value
Once a running program is interrupted in gdb, we can also inspect the valueof a variable using the ’print’ command.
If we are interested about the current value of variable a, wecan simply ’print variable_name’. For example, after line 8 is executed, wecan inspect if the atoi function correctly translate the characters tointeger as below:
Similiarly, if we are interested about the current value of a register, wecan simply ’print $register_name’. For example, after line 8 is executed, wecan inspect $eax as:
If we are interested about all the register values, we can use ’inforegisters’ command to display the value in all registers.
Download here: http://gg.gg/wdc07

https://diarynote.indered.space