幻の上帝
2011-05-09 10:36:38
纯转，渣排版，日后研究：http://groups.google.com/group/vgcoding/browse_thread/thread/e311260aa3b37c12
发件人：Antonio Maiorano
日期：Mon, 17 Jan 2011 22:26:22 -0800 (PST)
当地时间：2011年1月18日(星期二) 上午1时26分
[Video Game Coding] How to debug your NDS rom using the Visual Studio Debugger
I have been working on Zelda DS for over a year now, and have loved the
experience of using the homebrew tools provided by devkitPro. However,
as the project grew, I quickly started to miss using a source-level
debugger to help me debug and fix problems in the code. There is a
debugger that you can download as part of devkitPro named Insight; but
it's a fairly finicky application, and is a far cry from the powerful
debugger I'm used to using on a daily basis: the Microsoft Visual
Studio debugger.
Well, the good news is, after much research and playing around, I found
a way to use the Visual Studio debugger to debug homebrew NDS roms!
I've decided to share these steps with you in this tutorial:
Requirements
You must have the following software installed:
- Visual Studio: A full copy of Visual Studio, not an Express edition,
I use version 2008, but 2005 and 2010 should work fine. The reason it
can't be the Express version of Visual Studio is that it does not
support plugins, and the next requirement is a plugin...
- WinGDB: This excellent plugin allows you to debug gcc compiled
programs with gdb within Visual Studio. It's not free, however before
you decide whether to purchase it, you can download a fully functional
30-day trial.
- DeSmuME: The best DS emulator available, and the only one that
implements a gdb stub that allows you to use gdb to debug an NDS rom.
Thankfully, this piece of software is not only free, but open source as
well!
Setup
Visual Studio Makefile Project
The first step is creating a Visual Studio Makefile project that simply
invokes the makefile for your homebrew NDS application, and often
includes the source files if you wish to use Visual Studio as an editor
as well. There is an excellent tutorial on how to do exactly this right
here:http://www.console-dev.de/2009/09/03/create-nintendo-ds-applications-...
The only difference in my setup is that I don't use no as my
emulator, but DeSmuME instead, which I discuss later. In any case, if
you can at least build your rom from a Visual Studio project, you're
good to go for the next step.
幻の上帝
2011-05-09 10:37:37
Compiling with Optimizations Disabled
In order to easily debug your NDS rom, you must disable compiler
optimizations, otherwise you'll find that stepping through code will
jump all over the place, and setting breakpoints won't always stay on
the lines you set them. This is normal since the order of generated
optimized code will often not match the order you specified in the
source code.
The devkitPro templates for NDS applications enable optimizations by
default. To disable them, open the Makefile, and find the line similar
to:
CFLAGS := -g -Wall -O2
-fomit-frame-pointer
-ffast-math
$(ARCH)
To disable optimizations, you must minimally remove the -O2.
Personally, I also remove the -fomit-frame-pointer and the -ffast-math
to make sure I don't get wonky behaviour when stepping through code,
but that may be overkill.
Once you've modified the Makefile, make sure to rebuild your rom. An
incremental build will not work since no dependencies have changed.
As a side note, you'll probably want to reenable optimizations for your
final NDS rom, especially if you notice a performance hit from having
disabled them. Having to do this by manually editing the Makefile every
time can be tedious. Personally, I made many modifications to the
Makefiles that allow me to pass in a configuration (DEBUG or RELEASE),
which modifies not only the compiler flags, but also the output folder
for object files, and the name of the rom itself. I may post a tutorial
on how to do this someday.
WinGDB Setup
Assuming you've installed Visual Studio and WinGDB correctly, you
should see an menu entry for WinGDB in Visual Studio:
Select WinGDB → Preferences, General tab, the only option you'll need
to set is the Default debugger path to the arm-eabi-gdb.exe in your
devkitPro installation, which in my case
is "C:devkitProdevkitARMinarm-eabi-gdb.exe":
Click OK to close the dialog. Now we need to set the project-specific
properties for WinGDB. To do this, in the Solution Explorer,
right-click on your project and select WinGDB → Properties:
Now set the following fields in the dialog that opens:
General tab, Target type: Embedded Linux system (gdbserver)
Debug tab:
Executable path: here you must set the path to the arm9 elf file that
gets built for your application. The arm9 elf file contains the code,
data, and debug information for the arm9 processor, and is usually what
you're interested in debugging. Note that if you used the arm9 template
from devkitPro (i.e. c:devkitProexamples
ds emplatesarm9), there
should be only one elf file that gets built next to your nds file.
However, if you used the combined template (i.e.
c:devkitProexamples
ds emplatescombined), you'll find the elf file
within the arm9 subfolder with extension .arm9.elf.
Stop in main(): yes (I find it useful, but it's really up to you)
Byte order: little endian
And finally, on the Target tab, set Target specification to: remote
localhost:20000
What this value means is that we want gdb to connect to a remote gdb
stub that is listening on the local machine's port 20000, which is what
we'll set up DeSmuME to do.
Now click OK to save your settings. For the curious, these settings are
saved in your project's .suo (user options) file.
幻の上帝
2011-05-09 10:37:45
Debugging
Launch DeSmuME
Now it's time to debug your rom! The first step is to launch the
development version of DeSmuME with a specific argument telling it to
enable the gdb stub code and to listen on localhost:20000. For example,
I run the following command:
c:emusdesmumeDeSmuME_dev.exe --arm9gdb=20000
C:codingeldaDSeldaDS_d.nds
A few things to note:
- You must use the "_dev" executable
- We specify that we want to debug the arm9 processor. You can instead
specify arm7gdb as well if you wish (and set WinGDB to debug the arm7
elf file instead).
- The port number, 20000, must match the one set in WinGDB. You can
change this value as long as the two match. This will launch DeSmuME
with a console window, and if all went well, the console should report
that your nds was loaded succesfully, Emulation unpaused, and the main
DeSmuME window should not yet be running your game. DeSmuME is
effectively waiting for gdb to connect to it.
Note: since you'll be doing this often, it's a good idea to create a
batch file that runs the above command line. What I did was add a an
External Tool to the Tools menu in Visual Studio so that I can easily
launch DeSmuME within the IDE.
Launch Visual Studio Debugger via WinGDB
With your project loaded in Visual Studio, from the menu select WinGDB
→ Start Debugging and if all goes well, Visual Studio should switch
into debugging mode, and you should eventually break on the first line
of main()!
From here, you can do pretty much anything you can normally do in the
Visual Studio Debugger, which includes, but is not limited to:
- Setting breakpoints (conditional, tracepoints, etc.)
- Hovering over variables to see their values
- Using the autos, locals, watch, memory and threads windows
- Using the disassembly view to see your source code mixed with the
assembly code that was generated
- Setting a breakpoint at arbitrary locations while your application is
running (this has never worked for me with other debuggers like Insight
or Eclipse).
Conclusion
Phew, that was a little longer than I thought it would be, but
hopefully this tutorial will help some of you debug your NDS
applications more easily! If you have any problems, or if you feel
certain parts of this tutorial could be more clear, don't hesitate to
let me know.
--
Posted By Antonio Maiorano to Video Game Coding at 1/18/2011 01:26:00 AM
牧濑红莉栖
2011-05-09 10:39:19
你确定你看得懂？
710895609
2011-05-09 10:40:18
＊＊看不懂
苹果君
2011-05-09 11:13:10
第一次发现自己英语原来那么烂…
雷精灵
2011-05-09 11:19:42
抽空本少爷翻译一下。虽然对于拥有官方开发设备的本少爷来说，这文章用处不大，但对于其他自制软件开发者来说，这篇教程或许还真是好东西。
牧濑红莉栖
2011-05-09 11:25:45
惊现雷叔。
菠菜很无奈
2011-05-09 11:33:44
从来对我的英语不报信心…
huxiaowansui
2011-05-09 11:37:09
天书啊啥也看不懂
yht19921212
2011-05-09 11:49:45
作为国民自豪的宣布：英语啥的不擅长
幻の上帝
2011-05-09 12:28:33
（排版坑爹应该只是在线代理的关系……）
VS2010基本试验成功。
其实有单步/断点/监视堆栈就够用了……= =
话说DeSmuME的dev没x64的么……
boy545003571
2011-05-09 14:05:28
@_@ 求翻译。。。