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<chapter id="debugger">
<title>Debugging Wine</title>
<sect1 id="dbg-intro">
<title>Introduction</title>
<sect2>
<title>Processes and threads: in underlying OS and in Windows</title>
<para>
Before going into the depths of debugging in Wine, here's
a small overview of process and thread handling in Wine.
It has to be clear that there are two different beasts:
processes/threads from the Unix point of view and
processes/threads from a Windows point of view.
</para>
<para>
Each Windows' thread is implemented as a Unix thread, meaning
that all threads of a same Windows' process share the same
(unix) address space.
</para>
<para>
In the following:
</para>
<itemizedlist>
<listitem>
<para>
<varname>W-process</varname> means a process in Windows' terminology
</para>
</listitem>
<listitem>
<para>
<varname>U-process</varname> means a process in Unix' terminology
</para>
</listitem>
<listitem>
<para>
<varname>W-thread</varname> means a thread in Windows' terminology
</para>
</listitem>
</itemizedlist>
<para>
A <varname>W-process</varname> is made of one or several
<varname>W-threads</varname>. Each
<varname>W-thread</varname> is mapped to one and only one
<varname>U-process</varname>. All
<varname>U-processes</varname> of a same
<varname>W-process</varname> share the same address space.
</para>
<para>
Each Unix process can be identified by two values:
</para>
<itemizedlist>
<listitem>
<para>
the Unix process id (<varname>upid</varname> in the following)
</para>
</listitem>
<listitem>
<para>
the Windows's thread id (<varname>tid</varname>)
</para>
</listitem>
</itemizedlist>
<para>
Each Windows' process has also a Windows' process id
(<varname>wpid</varname> in the following). It must be clear
that <varname>upid</varname> and <varname>wpid</varname> are
different and shall not be used instead of the other.
</para>
<para>
<varname>Wpid</varname> and <varname>tid</varname> are
defined (Windows) system wide. They must not be confused
with process or thread handles which, as any handle, is an
indirection to a system object (in this case process or
thread). A same process can have several different handles
on the same kernel object. The handles can be defined as
local (the values is only valid in a process), or system
wide (the same handle can be used by any
<varname>W-process</varname>).
</para>
</sect2>
<sect2>
<title>Wine, debugging and WineDbg</title>
<para>
When talking of debugging in Wine, there are at least two
levels to think of:
</para>
<itemizedlist>
<listitem>
<para>
the Windows' debugging API.
</para>
</listitem>
<listitem>
<para>
the Wine integrated debugger, dubbed <command>winedbg</command>.
</para>
</listitem>
</itemizedlist>
<para>
Wine implements most of the Windows' debugging API. The
first part of the debugging APIs (in
<filename>KERNEL32.DLL</filename>) allows a W-process, called
the debugger, to control the execution of another W-process,
the debuggee. To control means stopping/resuming execution,
enabling/disabling single stepping, setting breakpoints,
reading/writing debuggee memory... Another part of the
debugging APIs resides in <filename>DBGHELP.DLL</filename>
(and its ancestor <filename>IMAGEHLP.DLL</filename>) and lets
a debugger look into symbols and types from any module (if
the module has been compiled with the proper options).
</para>
<para>
<command>winedbg</command> is a Winelib application making
use of these APIs (<filename>KERNEL32.DLL</filename>'s
debugging API and <filename>DBGHELP.DLL</filename>) to allow
debugging both any Wine or Winelib applications as well as
Wine itself (kernel and all DLLs).
</para>
</sect2>
</sect1>
<sect1 id="dbg-modes">
<title>WineDbg's modes of invocation</title>
<sect2>
<title>Starting a process</title>
<para>
Any application (either a Windows' native executable, or a
Winelib application) can be run through
<command>winedbg</command>. Command line options and tricks
are the same as for wine:
</para>
<screen>
winedbg telnet.exe
winedbg hl.exe -windowed
</screen>
</sect2>
<sect2>
<title>Attaching</title>
<para>
<command>winedbg</command> can also be launched without any
command line argument: <command>winedbg</command> is started
without any attached process. You can get a list of running
<varname>W-processes</varname> (and their
<varname>wpid</varname>'s) using the <command>info
process</command> command, and then, with the
<command>attach</command> command, pick up the
<varname>wpid</varname> of the <varname>W-process</varname>
you want to debug. This is a neat feature as it allows you
to debug an already started application.
</para>
</sect2>
<sect2 id="dbg-on-exception">
<title id="dbg-exception-title">On exceptions</title>
<para>
When something goes wrong, Windows tracks this as an
exception. Exceptions exist for segmentation violation,
stack overflow, division by zero, etc.
</para>
<para>
When an exception occurs, Wine checks if the
<varname>W-process</varname> is debugged. If so, the
exception event is sent to the debugger, which takes care of
it: end of the story. This mechanism is part of the standard
Windows' debugging API.
</para>
<para>
If the <varname>W-process</varname> is not debugged, Wine
tries to launch a debugger. This debugger (normally
<command>winedbg</command>, see III Configuration for more
details), at startup, attaches to the
<varname>W-process</varname> which generated the exception
event. In this case, you are able to look at the causes of
the exception, and either fix the causes (and continue
further the execution) or dig deeper to understand what went
wrong.
</para>
<para>
If <command>winedbg</command> is the standard debugger, the
<command>pass</command> and <command>cont</command> commands
are the two ways to let the process go further for the
handling of the exception event.
</para>
<para>
To be more precise on the way Wine (and Windows) generates
exception events, when a fault occurs (segmentation
violation, stack overflow...), the event is first sent to
the debugger (this is known as a first chance exception).
The debugger can give two answers:
</para>
<variablelist>
<varlistentry>
<term>continue</term>
<listitem>
<para>
the debugger had the ability to correct what's
generated the exception, and is now able to continue
process execution.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>pass</term>
<listitem>
<para>
the debugger couldn't correct the cause of the
first chance exception. Wine will now try to walk
the list of exception handlers to see if one of them
can handle the exception. If no exception handler is
found, the exception is sent once again to the
debugger to indicate the failure of the exception
handling.
</para>
</listitem>
</varlistentry>
</variablelist>
<note>
<para>
since some of Wine's code uses exceptions and
<function>try/catch</function> blocks to provide some
functionality, <command>winedbg</command> can be entered
in such cases with segv exceptions. This happens, for
example, with <function>IsBadReadPtr</function> function.
In that case, the <command>pass</command> command shall be
used, to let the handling of the exception to be done by
the <function>catch</function> block in
<function>IsBadReadPtr</function>.
</para>
</note>
</sect2>
<sect2 id="interrupt">
<title>Interrupting</title>
<para>
You can stop the debugger while it's running by hitting
Ctrl-C in its window. This will stop the debugged process,
and let you manipulate the current context.
</para>
</sect2>
<sect2>
<title>Quitting</title>
<para>
Wine supports the new XP APIs, allowing for a debugger to
detach from a program being debugged (see
<command>detach</command> command).
</para>
</sect2>
</sect1>
<sect1 id="wine-debugger">
<title>Using the Wine Debugger</title>
<para>
This section describes where to start debugging Wine. If at any
point you get stuck and want to ask for help, please read the
<emphasis>How to Report A Bug</emphasis> section of the
<emphasis>Wine Users Guide</emphasis> for information on how to write
useful bug reports.
</para>
<sect2>
<title>Crashes</title>
<para>
These usually show up like this:
</para>
<screen>
|Unexpected Windows program segfault - opcode = 8b
|Segmentation fault in Windows program 1b7:c41.
|Loading symbols from ELF file /root/wine/wine...
|....more Loading symbols from ...
|In 16 bit mode.
|Register dump:
| CS:01b7 SS:016f DS:0287 ES:0000
| IP:0c41 SP:878a BP:8796 FLAGS:0246
| AX:811e BX:0000 CX:0000 DX:0000 SI:0001 DI:ffff
|Stack dump:
|0x016f:0x878a: 0001 016f ffed 0000 0000 0287 890b 1e5b
|0x016f:0x879a: 01b7 0001 000d 1050 08b7 016f 0001 000d
|0x016f:0x87aa: 000a 0003 0004 0000 0007 0007 0190 0000
|0x016f:0x87ba:
|
|0050: sel=0287 base=40211d30 limit=0b93f (bytes) 16-bit rw-
|Backtrace:
|0 0x01b7:0x0c41 (PXSRV_FONGETFACENAME+0x7c)
|1 0x01b7:0x1e5b (PXSRV_FONPUTCATFONT+0x2cd)
|2 0x01a7:0x05aa
|3 0x01b7:0x0768 (PXSRV_FONINITFONTS+0x81)
|4 0x014f:0x03ed (PDOXWIN_@SQLCURCB$Q6CBTYPEULN8CBSCTYPE+0x1b1)
|5 0x013f:0x00ac
|
|0x01b7:0x0c41 (PXSRV_FONGETFACENAME+0x7c): movw %es:0x38(%bx),%dx
</screen>
<para>
Steps to debug a crash. You may stop at any step, but please
report the bug and provide as much of the information
gathered to the bug report as feasible.
</para>
<orderedlist>
<listitem>
<para>
Get the reason for the crash. This is usually an access to
an invalid selector, an access to an out of range address
in a valid selector, popping a segment register from the
stack or the like. When reporting a crash, report this
<emphasis>whole</emphasis> crashdump even if it doesn't
make sense to you.
</para>
<para>
(In this case it is access to an invalid selector, for
<systemitem>%es</systemitem> is <literal>0000</literal>, as
seen in the register dump).
</para>
</listitem>
<listitem>
<para>
Determine the cause of the crash. Since this is usually
a primary/secondary reaction to a failed or misbehaving
Wine function, rerun Wine with the<parameter>WINEDEBUG=+relay</parameter>
environment variable set. This will
generate quite a lot of output, but usually the reason is
located in the last call(s). Those lines usually look like
this:
</para>
<screen>
|Call KERNEL.90: LSTRLEN(0227:0692 "text") ret=01e7:2ce7 ds=0227
^^^^^^^^^ ^ ^^^^^^^^^ ^^^^^^ ^^^^^^^^^ ^^^^
| | | | | |Datasegment
| | | | |Return address
| | | |textual parameter
| | |
| | |Argument(s). This one is a win16 segmented pointer.
| |Function called.
|The module, the function is called in. In this case it is KERNEL.
|Ret KERNEL.90: LSTRLEN() retval=0x0004 ret=01e7:2ce7 ds=0227
^^^^^^
|Returnvalue is 16 bit and has the value 4.
</screen>
</listitem>
<listitem>
<para>
If you have found a misbehaving function, try to find out
why it misbehaves. Find the function in the source code.
Try to make sense of the arguments passed. Usually there is
a <function>WINE_DEFAULT_DEBUG_CHANNEL(&lt;channel>);</function>
at the beginning of the file. Rerun wine with the
<parameter>WINEDEBUG=+xyz,+relay</parameter> environment variable set.
</para>
<para>
Occasionally there are additional debug channels defined at the
beginning of the file in the form.
<function>WINE_DECLARE_DEBUG_CHANNEL(&lt;channel>);</function>
If so the offending function may also uses one of these alternate
channels. Look through the the function for
<function>TRACE_(&lt;channel>)(" ... /n");</function> and add any
additional channels to the commandline.
</para>
</listitem>
<listitem>
<para>
Additional information on how to debug using the internal
debugger can be found in
<filename>programs/winedbg/README</filename>.
</para>
</listitem>
<listitem>
<para>
If this information isn't clear enough or if you want to
know more about what's happening in the function itself,
try running wine with <parameter>WINEDEBUG=+all</parameter>,
which dumps ALL included debug
information in wine.
</para>
</listitem>
<listitem>
<para>
If even that isn't enough, add more debug output for yourself
into the functions you find relevant. See The section on Debug
Logging in this guide for more information. You might
also try to run the program in <command>gdb</command>
instead of using the Wine debugger. If you do that, use
<parameter>handle SIGSEGV nostop noprint</parameter> to
disable the handling of seg faults inside
<command>gdb</command> (needed for Win16).
</para>
</listitem>
<listitem>
<para>
You can also set a breakpoint for that function. Start wine
useing <command>winedbg</command> instead of
<command>wine</command>. Once the debugger is is running enter
<command>break</command> <parameter>KERNEL_LSTRLEN</parameter>
(replace by function you want to debug, CASE IS RELEVANT)
to set a breakpoint. Then
use <command>continue</command> to start normal
program-execution. Wine will stop if it reaches the
breakpoint. If the program isn't yet at the crashing call
of that function, use <command>continue</command> again
until you are about to enter that function. You may now
proceed with single-stepping the function until you reach
the point of crash. Use the other debugger commands to
print registers and the like.
</para>
</listitem>
</orderedlist>
</sect2>
<sect2>
<title>Program hangs, nothing happens</title>
<para>
Start the program with <command>winedbg</command> instead of
<command>wine</command>. When the program locks up switch to the
winedbg's terminal and press
<keycombo><keycap>Ctrl</keycap><keycap>C</keycap></keycombo>. this
will stop the program and let you debug the program as you would for
a crash.
</para>
</sect2>
<sect2>
<title>Program reports an error with a Messagebox</title>
<para>
Sometimes programs are reporting failure using more or
less nondescript messageboxes. We can debug this using the
same method as Crashes, but there is one problem... For
setting up a message box the program also calls Wine
producing huge chunks of debug code.
</para>
<para>
Since the failure happens usually directly before setting up
the Messagebox you can start winedbg and set a
breakpoint at <function>MessageBoxA</function> (called by win16
and win32 programs) and proceed with
<command>continue</command>. With <parameter>WINEDEBUG=+all</parameter>
Wine will now stop directly before setting
up the Messagebox. Proceed as explained above.
</para>
<para>
You can also run wine using <command>WINEDEBUG=+relay wine
program.exe 2>&1 | less -i</command> and in
<command>less</command> search for <quote>MessageBox</quote>.
</para>
</sect2>
<sect2>
<title>Disassembling programs</title>
<para>
You may also try to disassemble the offending program to
check for undocumented features and/or use of them.
</para>
<para>
The best, freely available, disassembler for Win16 programs is
<application>Windows Codeback</application>, archive name
<filename>wcbxxx.zip</> (e.g. <filename>wcb105a.zip</>), which
usually can be found in the <filename>Cica-Mirror</filename>
subdirectory on the Wine ftp sites. (See <filename>ANNOUNCE</>).
</para>
<para>
Disassembling win32 programs is possible using
<application>Windows Disassembler 32</>. Look for
a file called <filename>w32dsm87.zip</> (or similar)
on <ulink url="http://www.winsite.com/">http://www.winsite.com</>
and mirrors. The shareware version does not allow saving of
disassembly listings. You can also use the newer (and in the
full version better) <application>Interactive
Disassembler</application> (IDA) from the ftp sites mentioned
at the end of the document. Understanding disassembled code is
mostly a question of exercise.
</para>
<para>
Most code out there uses standard C function entries (for it
is usually written in C). Win16 function entries usually
look like that:
</para>
<programlisting>
push bp
mov bp, sp
... function code ..
retf XXXX &lt;--------- XXXX is number of bytes of arguments
</programlisting>
<para>
This is a <function>FAR</function> function with no local
storage. The arguments usually start at
<literal>[bp+6]</literal> with increasing offsets. Note, that
<literal>[bp+6]</literal> belongs to the
<emphasis>rightmost</emphasis> argument, for exported win16
functions use the PASCAL calling convention. So, if we use
<function>strcmp(a,b)</function> with <parameter>a</parameter>
and <parameter>b</parameter> both 32 bit variables
<parameter>b</parameter> would be at <literal>[bp+6]</literal>
and <parameter>a</parameter> at <literal>[bp+10]</literal>.
</para>
<para>
Most functions make also use of local storage in the stackframe:
</para>
<programlisting>
enter 0086, 00
... function code ...
leave
retf XXXX
</programlisting>
<para>
This does mostly the same as above, but also adds
<literal>0x86</literal> bytes of stackstorage, which is
accessed using <literal>[bp-xx]</literal>. Before calling a
function, arguments are pushed on the stack using something
like this:
</para>
<programlisting>
push word ptr [bp-02] &lt;- will be at [bp+8]
push di &lt;- will be at [bp+6]
call KERNEL.LSTRLEN
</programlisting>
<para>
Here first the selector and then the offset to the passed
string are pushed.
</para>
</sect2>
<sect2>
<title>Sample debugging session</title>
<para>
Let's debug the infamous Word <filename>SHARE.EXE</filename>
messagebox:
</para>
<screen>
|marcus@jet $ wine winword.exe
| +---------------------------------------------+
| | ! You must leave Windows and load SHARE.EXE|
| | before starting Word. |
| +---------------------------------------------+
</screen>
<screen>
|marcus@jet $ WINEDEBUG=+relay,-debug wine winword.exe
|CallTo32(wndproc=0x40065bc0,hwnd=000001ac,msg=00000081,wp=00000000,lp=00000000)
|Win16 task 'winword': Breakpoint 1 at 0x01d7:0x001a
|CallTo16(func=0127:0070,ds=0927)
|Call WPROCS.24: TASK_RESCHEDULE() ret=00b7:1456 ds=0927
|Ret WPROCS.24: TASK_RESCHEDULE() retval=0x8672 ret=00b7:1456 ds=0927
|CallTo16(func=01d7:001a,ds=0927)
| AX=0000 BX=3cb4 CX=1f40 DX=0000 SI=0000 DI=0927 BP=0000 ES=11f7
|Loading symbols: /home/marcus/wine/wine...
|Stopped on breakpoint 1 at 0x01d7:0x001a
|In 16 bit mode.
|Wine-dbg>break MessageBoxA &lt;---- Set Breakpoint
|Breakpoint 2 at 0x40189100 (MessageBoxA [msgbox.c:190])
|Wine-dbg>c &lt;---- Continue
|Call KERNEL.91: INITTASK() ret=0157:0022 ds=08a7
| AX=0000 BX=3cb4 CX=1f40 DX=0000 SI=0000 DI=08a7 ES=11d7 EFL=00000286
|CallTo16(func=090f:085c,ds=0dcf,0x0000,0x0000,0x0000,0x0000,0x0800,0x0000,0x0000,0x0dcf)
|... &lt;----- Much debugoutput
|Call KERNEL.136: GETDRIVETYPE(0x0000) ret=060f:097b ds=0927
^^^^^^ Drive 0 (A:)
|Ret KERNEL.136: GETDRIVETYPE() retval=0x0002 ret=060f:097b ds=0927
^^^^^^ DRIVE_REMOVEABLE
(It is a floppy diskdrive.)
|Call KERNEL.136: GETDRIVETYPE(0x0001) ret=060f:097b ds=0927
^^^^^^ Drive 1 (B:)
|Ret KERNEL.136: GETDRIVETYPE() retval=0x0000 ret=060f:097b ds=0927
^^^^^^ DRIVE_CANNOTDETERMINE
(I don't have drive B: assigned)
|Call KERNEL.136: GETDRIVETYPE(0x0002) ret=060f:097b ds=0927
^^^^^^^ Drive 2 (C:)
|Ret KERNEL.136: GETDRIVETYPE() retval=0x0003 ret=060f:097b ds=0927
^^^^^^ DRIVE_FIXED
(specified as a harddisk)
|Call KERNEL.97: GETTEMPFILENAME(0x00c3,0x09278364"doc",0x0000,0927:8248) ret=060f:09b1 ds=0927
^^^^^^ ^^^^^ ^^^^^^^^^
| | |buffer for fname
| |temporary name ~docXXXX.tmp
|Force use of Drive C:.
|Warning: GetTempFileName returns 'C:~doc9281.tmp', which doesn't seem to be writeable.
|Please check your configuration file if this generates a failure.
</screen>
<para>
Whoops, it even detects that something is wrong!
</para>
<screen>
|Ret KERNEL.97: GETTEMPFILENAME() retval=0x9281 ret=060f:09b1 ds=0927
^^^^^^ Temporary storage ID
|Call KERNEL.74: OPENFILE(0x09278248"C:~doc9281.tmp",0927:82da,0x1012) ret=060f:09d8 ds=0927
^^^^^^^^^^^^^^^^ ^^^^^^^^^ ^^^^^^^
|filename |OFSTRUCT |open mode:
OF_CREATE|OF_SHARE_EXCLUSIVE|OF_READWRITE
</screen>
<para>
This fails, since my <medialabel>C:</medialabel> drive is in
this case mounted readonly.
</para>
<screen>
|Ret KERNEL.74: OPENFILE() retval=0xffff ret=060f:09d8 ds=0927
^^^^^^ HFILE_ERROR16, yes, it failed.
|Call USER.1: MESSAGEBOX(0x0000,0x09278376"You must close Windows and load SHARE.EXE before you start Word.",0x00000000,0x1030) ret=060f:084f ds=0927
</screen>
<para>
And MessageBox'ed.
</para>
<screen>
|Stopped on breakpoint 2 at 0x40189100 (MessageBoxA [msgbox.c:190])
|190 { &lt;- the sourceline
In 32 bit mode.
Wine-dbg>
</screen>
<para>
The code seems to find a writeable harddisk and tries to create
a file there. To work around this bug, you can define
<medialabel>C:</medialabel> as a networkdrive, which is ignored
by the code above.
</para>
</sect2>
<sect2>
<title>Debugging Tips</title>
<para>
Here are some additional debugging tips:
</para>
<itemizedlist>
<listitem>
<para>
If you have a program crashing at such an early loader phase that you can't
use the Wine debugger normally, but Wine already executes the program's
start code, then you may use a special trick. You should do a
<programlisting>
WINEDEBUG=+relay wine program
</programlisting>
to get a listing of the functions the program calls in its start function.
Now you do a
<programlisting>
winedbg winfile.exe
</programlisting>
</para>
<para>
This way, you get into <command>winedbg</command>. Now you
can set a breakpoint on any function the program calls in
the start function and just type <userinput>c</userinput>
to bypass the eventual calls of Winfile to this function
until you are finally at the place where this function gets
called by the crashing start function. Now you can proceed
with your debugging as usual.
</para>
</listitem>
<listitem>
<para>
If you try to run a program and it quits after showing an error messagebox,
the problem can usually be identified in the return value of one of the
functions executed before <function>MessageBox()</function>.
That's why you should re-run the program with e.g.
<programlisting>
WINEDEBUG=+relay wine &lt;program name> &>relmsg
</programlisting>
Then do a <command>more relmsg</command> and search for the
last occurrence of a call to the string "MESSAGEBOX". This is a line like
<programlisting>
Call USER.1: MESSAGEBOX(0x0000,0x01ff1246 "Runtime error 219 at 0004:1056.",0x00000000,0x1010) ret=01f7:2160 ds=01ff
</programlisting>
In my example the lines before the call to
<function>MessageBox()</function> look like that:
<programlisting>
Call KERNEL.96: FREELIBRARY(0x0347) ret=01cf:1033 ds=01ff
CallTo16(func=033f:0072,ds=01ff,0x0000)
Ret KERNEL.96: FREELIBRARY() retval=0x0001 ret=01cf:1033 ds=01ff
Call KERNEL.96: FREELIBRARY(0x036f) ret=01cf:1043 ds=01ff
CallTo16(func=0367:0072,ds=01ff,0x0000)
Ret KERNEL.96: FREELIBRARY() retval=0x0001 ret=01cf:1043 ds=01ff
Call KERNEL.96: FREELIBRARY(0x031f) ret=01cf:105c ds=01ff
CallTo16(func=0317:0072,ds=01ff,0x0000)
Ret KERNEL.96: FREELIBRARY() retval=0x0001 ret=01cf:105c ds=01ff
Call USER.171: WINHELP(0x02ac,0x01ff05b4 "COMET.HLP",0x0002,0x00000000) ret=01cf:1070 ds=01ff
CallTo16(func=0117:0080,ds=01ff)
Call WPROCS.24: TASK_RESCHEDULE() ret=00a7:0a2d ds=002b
Ret WPROCS.24: TASK_RESCHEDULE() retval=0x0000 ret=00a7:0a2d ds=002b
Ret USER.171: WINHELP() retval=0x0001 ret=01cf:1070 ds=01ff
Call KERNEL.96: FREELIBRARY(0x01be) ret=01df:3e29 ds=01ff
Ret KERNEL.96: FREELIBRARY() retval=0x0000 ret=01df:3e29 ds=01ff
Call KERNEL.52: FREEPROCINSTANCE(0x02cf00ba) ret=01f7:1460 ds=01ff
Ret KERNEL.52: FREEPROCINSTANCE() retval=0x0001 ret=01f7:1460 ds=01ff
Call USER.1: MESSAGEBOX(0x0000,0x01ff1246 "Runtime error 219 at 0004:1056.",0x00000000,0x1010) ret=01f7:2160 ds=01ff
</programlisting>
</para>
<para>
I think that the call to <function>MessageBox()</function>
in this example is <emphasis>not</emphasis> caused by a
wrong result value of some previously executed function
(it's happening quite often like that), but instead the
messagebox complains about a runtime error at
<literal>0x0004:0x1056</literal>.
</para>
<para>
As the segment value of the address is only
<literal>4</literal>, I think that that is only an internal
program value. But the offset address reveals something
quite interesting: Offset <literal>1056</literal> is
<emphasis>very</emphasis> close to the return address of
<function>FREELIBRARY()</function>:
<programlisting>
Call KERNEL.96: FREELIBRARY(0x031f) ret=01cf:105c ds=01ff
^^^^
</programlisting>
</para>
<para>
Provided that segment <literal>0x0004</literal> is indeed segment
<literal>0x1cf</literal>, we now we can use IDA (available at
<ulink url="http://www.filelibrary.com:8080/cgi-bin/freedownload/DOS/h/72/ida35bx.zip">
http://www.filelibrary.com:8080/cgi-bin/freedownload/DOS/h/72/ida35bx.zip</ulink>) to
disassemble the part that caused the error. We just have to find the address of
the call to <function>FreeLibrary()</function>. Some lines before that the
runtime error occurred. But be careful! In some cases you don't have to
disassemble the main program, but instead some DLL called by it in order to find
the correct place where the runtime error occurred. That can be determined by
finding the origin of the segment value (in this case <literal>0x1cf</literal>).
</para>
</listitem>
<listitem>
<para>
If you have created a relay file of some crashing
program and want to set a breakpoint at a certain
location which is not yet available as the program loads
the breakpoint's segment during execution, you may set a
breakpoint to <function>GetVersion16/32</function> as
those functions are called very often.
</para>
<para>
Then do a <userinput>c</userinput> until you are able to
set this breakpoint without error message.
</para>
</listitem>
<listitem>
<para>
Some useful programs:
</para>
<variablelist>
<varlistentry>
<term>
<application>IDA</application>:
<filename>
<ulink url="http://www.filelibrary.com:8080/cgi-bin/freedownload/DOS/h/72/ida35bx.zip">
http://www.filelibrary.com:8080/cgi-bin/freedownload/DOS/h/72/ida35bx.zip</ulink>
</filename>
</term>
<listitem>
<para>
<emphasis>Very</emphasis> good DOS disassembler ! It's badly needed
for debugging Wine sometimes.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<application>XRAY</application>:
<filename>
<ulink url="http://garbo.uwasa.fi/pub/pc/sysinfo/xray15.zip">
http://garbo.uwasa.fi/pub/pc/sysinfo/xray15.zip</ulink>
</filename>
</term>
<listitem>
<para>
Traces DOS calls (Int 21h, DPMI, ...). Use it with
Windows to correct file management problems etc.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<application>pedump</application>:
<filename>
<ulink url="ftp://ftp.simtel.net/pub/simtelnet/win95/prog/pedump.zip">
ftp://ftp.simtel.net/pub/simtelnet/win95/prog/pedump.zip</ulink>
</filename>
</term>
<listitem>
<para>
Dumps the imports and exports of a PE (Portable
Executable) DLL.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<application>winedump</application>:
</term>
<listitem>
<para>
Dumps the imports and exports of a PE (Portable
Executable) DLL (included in wine tree).
</para>
</listitem>
</varlistentry>
</variablelist>
</listitem>
</itemizedlist>
</sect2>
<sect2>
<title>Some basic debugger usages</title>
<para>
After starting your program with
</para>
<screen>
wine -debug myprog.exe
</screen>
<para>
the program loads and you get a prompt at the program
starting point. Then you can set breakpoints:
</para>
<screen>
b RoutineName (by routine name) OR
b *0x812575 (by address)
</screen>
<para>
Then you hit <command>c</command> (continue) to run the
program. It stops at the breakpoint. You can type
</para>
<screen>
step (to step one line) OR
stepi (to step one machine instruction at a time;
here, it helps to know the basic 386
instruction set)
info reg (to see registers)
info stack (to see hex values in the stack)
info local (to see local variables)
list &lt;line number&gt; (to list source code)
x &lt;variable name&gt; (to examine a variable; only works if code
is not compiled with optimization)
x 0x4269978 (to examine a memory location)
? (help)
q (quit)
</screen>
<para>
By hitting <keycap>Enter</keycap>, you repeat the last
command.
</para>
</sect2>
</sect1>
<sect1 id="memory-addresses">
<title>Useful memory addresses</title>
<para>
Wine uses several different kinds of memory addresses.
</para>
<variablelist>
<varlistentry>
<term>
Win32/"normal" Wine addresses/Linux: linear addresses.
</term>
<listitem>
<para>
Linear addresses can be everything from 0x0 up to
0xffffffff. In Wine on Linux they are often around
e.g. 0x08000000, 0x00400000 (std. Win32 program load
address), 0x40000000. Every Win32 process has its own
private 4GB address space (that is, from 0x0 up to
0xffffffff).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
Win16 "enhanced mode": segmented addresses.
</term>
<listitem>
<para>
These are the "normal" Win16 addresses, called SEGPTR.
They have a segment:offset notation, e.g. 0x01d7:0x0012.
The segment part usually is a "selector", which
<emphasis>always</emphasis>
has the lowest 3 bits set. Some sample selectors are
0x1f7, 0x16f, 0x8f. If these bits are set except for
the lowest bit, as e.g. with 0x1f6,xi then it might be a
handle to global memory. Just set the lowest bit to get
the selector in these cases. A selector kind of
"points" to a certain linear (see above) base address.
It has more or less three important attributes: segment
base address, segment limit, segment access rights.
</para>
<para>
Example:
</para>
<para>
Selector 0x1f7 (0x40320000, 0x0000ffff, r-x) So 0x1f7
has a base address of 0x40320000, the segment's last
address is 0x4032ffff (limit 0xffff), and it's readable
and executable. So an address of 0x1f7:0x2300 would be
the linear address of 0x40322300.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
DOS/Win16 "standard mode"
</term>
<listitem>
<para>
They, too, have a segment:offset notation. But they are
completely different from "normal" Win16 addresses, as
they just represent at most 1MB of memory: The segment
part can be anything from 0 to 0xffff, and it's the same
with the offset part.
</para>
<para>
Now the strange thing is the calculation that's behind
these addresses: Just calculate segment*16 + offset in
order to get a "linear DOS" address. So
e.g. 0x0f04:0x3628 results in 0xf040 + 0x3628 = 0x12668.
And the highest address you can get is 0xfffff (1MB), of
course. In Wine, this "linear DOS" address of 0x12668
has to be added to the linear base address of the
corresponding DOS memory allocated for dosmod in order
to get the true linear address of a DOS seg:offs
address. And make sure that you're doing this in the
correct process with the correct linear address space,
of course ;-)
</para>
</listitem>
</varlistentry>
</variablelist>
</sect1>
<sect1 id="dbg-config">
<title>Configuration</title>
<sect2>
<title>Registry configuration</title>
<para>
The Windows' debugging API uses a registry entry to know
which debugger to invoke when an unhandled exception occurs
(see <link endterm="dbg-exception-title"
linkend="dbg-on-exception"></link> for some details). Two
values in key
</para>
<programlisting>
"MACHINE\\Software\\Microsoft\\Windows NT\\CurrentVersion\\AeDebug"
</programlisting>
<para>
Determine the behavior:
</para>
<variablelist>
<varlistentry>
<term>Debugger</term>
<listitem>
<para>
this is the command line used to launch the debugger
(it uses two <function>printf</function> formats
(<literal>%ld</literal>) to pass context dependent
information to the debugger). You should put here a
complete path to your debugger
(<command>winedbg</command> can of course be used, but
any other Windows' debugging API aware debugger will
do).
The path to the debugger you chose to use must be reachable
via a DOS drive in the Wine config file !
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Auto</term>
<listitem>
<para>
if this value is zero, a message box will ask the
user if he/she wishes to launch the debugger when an
unhandled exception occurs. Otherwise, the debugger
is automatically started.
</para>
</listitem>
</varlistentry>
</variablelist>
<para>
A regular Wine registry looks like:
</para>
<programlisting>
[MACHINE\\Software\\Microsoft\\Windows NT\\CurrentVersion\\AeDebug] 957636538
"Auto"=dword:00000001
"Debugger"="winedbg %ld %ld"
</programlisting>
<note>
<title>Note 1</title>
<para>
creating this key is mandatory. Not doing so will not
fire the debugger when an exception occurs.
</para>
</note>
<note>
<title>Note 2</title>
<para>
<command>wineinstall</command> (available in Wine source)
sets up this correctly.
However, due to some limitation of the registry installed,
if a previous Wine installation exists, it's safer to
remove the whole
</para>
<programlisting>
[MACHINE\\Software\\Microsoft\\Windows NT\\CurrentVersion\\AeDebug]
</programlisting>
<para>
key before running again <command>wineinstall</command> to
regenerate this key.
</para>
</note>
</sect2>
<sect2>
<title>WineDbg configuration</title>
<para>
<command>winedbg</command> can be configured through a number
of options. Those options are stored in the registry, on a
per user basis. The key is (in <emphasis>my</emphasis> registry)
</para>
<programlisting>
[HKCU\\Software\\Wine\\WineDbg]
</programlisting>
<para>
Those options can be read/written while inside
<command>winedbg</command>, as part of the debugger
expressions. To refer to one of these options, its name must
be prefixed by a <literal>$</literal> sign. For example,
</para>
<programlisting>
set $BreakAllThreadsStartup = 1
</programlisting>
<para>
sets the option <varname>BreakAllThreadsStartup</varname> to
<literal>TRUE</literal>.
</para>
<para>
All the options are read from the registry when
<command>winedbg</command> starts (if no corresponding value
is found, a default value is used), and are written back to
the registry when <command>winedbg</command> exits (hence,
all modifications to those options are automatically saved
when <command>winedbg</command> terminates).
</para>
<para>
Here's the list of all options:
</para>
<variablelist>
<varlistentry>
<term><varname>BreakAllThreadsStartup</varname></term>
<listitem>
<para>
Set to <literal>TRUE</literal> if at all threads
start-up the debugger stops set to
<literal>FALSE</literal> if only at the first thread
startup of a given process the debugger
stops. <literal>FALSE</literal> by default.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>BreakOnCritSectTimeOut</varname></term>
<listitem>
<para>
Set to <literal>TRUE</literal> if the debugger stops
when a critical section times out (5 minutes);
<literal>TRUE</literal> by default.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>BreakOnAttach</varname></term>
<listitem>
<para>
Set to <literal>TRUE</literal> if when
<command>winedbg</command> attaches to an existing
process after an unhandled exception,
<command>winedbg</command> shall be entered on the
first attach event. Since the attach event is
meaningless in the context of an exception event (the
next event which is the exception event is of course
relevant), that option is likely to be
<literal>FALSE</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>BreakOnFirstChance</varname></term>
<listitem>
<para>
An exception can generate two debug events. The first
one is passed to the debugger (known as a first
chance) just after the exception. The debugger can
then decide either to resume execution (see
<command>winedbg</command>'s <command>cont</command>
command) or pass the exception up to the exception
handler chain in the program (if it exists)
(<command>winedbg</command> implements this through
the <command>pass</command> command). If none of the
exception handlers takes care of the exception, the
exception event is sent again to the debugger (known
as last chance exception). You cannot pass on a last
exception. When the
<varname>BreakOnFirstChance</varname> exception is
<literal>TRUE</literal>, then winedbg is entered for
both first and last chance execptions (to
<literal>FALSE</literal>, it's only entered for last
chance exceptions).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>AlwaysShowThunk</varname></term>
<listitem>
<para>
Set to <literal>TRUE</literal> if the debugger, when
looking up for a symbol from its name, displays all
the thunks with that name. The default value
(<literal>FALSE</literal>) allows not to have to
choose between a symbol and all the import thunks
from all the DLLs using that symbols.
</para>
</listitem>
</varlistentry>
</variablelist>
</sect2>
</sect1>
<sect1 id="dbg-expr">
<title>WineDbg Expressions and Variables</title>
<sect2>
<title>Expressions</title>
<para>
Expressions in Wine Debugger are mostly written in a C
form. However, there are a few discrepancies:
<itemizedlist>
<listitem>
<para>
Identifiers can take a '!' in their names. This allow
mainly to access symbols from different DLLs like
<function>USER32!CreateWindowExA</function>.
</para>
</listitem>
<listitem>
<para>
In cast operation, when specifying a structure or an
union, you must use the <type>struct</type> or
<type>union</type> keyword (even if your program uses a typedef).
</para>
</listitem>
</itemizedlist>
</para>
<para>
When specifying an identifier by its name, if several
symbols with the same name exist, the debugger will prompt
for the symbol you want to use. Pick up the one you want
from its number.
</para>
<para>
In lots of cases, you can also use regular expressions for
looking for a symbol.
</para>
<para>
<command>winedbg</command> defines its own set of
variables. The configuration variables from above are part
of them. Some others include:
<variablelist>
<varlistentry>
<term><varname>$ThreadId</varname></term>
<listitem>
<para>
ID of the <varname>W-thread</varname> currently
examined by the debugger
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>$ProcessId</varname></term>
<listitem>
<para>
ID of the <varname>W-thread</varname> currently
examined by the debugger
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>&lt;registers></term>
<listitem>
<para>
All CPU registers are also available, using $ as a
prefix. You can use <command>info regs</command> to
get a list of avaible CPU registers
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
The <varname>$ThreadId</varname> and
<varname>$ProcessId</varname> variables can be handy to set
conditional breakpoints on a given thread or process.
</para>
</sect2>
</sect1>
<sect1 id="dbg-commands">
<title>WineDbg Command Reference</title>
<sect2>
<title>Misc</title>
<para>
<table>
<title>WineDbg's misc. commands</title>
<tgroup cols="2" align="left">
<tbody>
<row>
<entry><command>abort</command></entry>
<entry>aborts the debugger</entry>
</row>
<row>
<entry><command>quit</command></entry>
<entry>exits the debugger</entry>
</row>
<row>
<entry><command>attach&nbsp;N</command></entry>
<entry>
attach to a W-process (N is its ID, numeric
or hexadecimal (0xN)). IDs can be obtained using
the info process command. Note the info process
command returns hexadecimal values.
</entry>
</row>
<row>
<entry><command>detach</command></entry>
<entry>detach from a W-process.</entry>
</row>
<row>
<entry><command>help</command></entry>
<entry>prints some help on the commands</entry>
</row>
<row>
<entry><command>help info</command></entry>
<entry>prints some help on info commands</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
</sect2>
<sect2>
<title>Flow control</title>
<para>
<table>
<title>WineDbg's flow control commands</title>
<tgroup cols="2" align="left">
<tbody>
<row>
<entry>
<msgtext>
<simplelist type="inline">
<member><command>cont</command></member>
<member><command>c</command></member>
</simplelist>
</msgtext>
</entry>
<entry>continue execution until next breakpoint or
exception.</entry>
</row>
<row>
<entry><command>pass</command></entry>
<entry>pass the exception event up to the filter
chain.</entry>
</row>
<row>
<entry>
<msgtext>
<simplelist type="inline">
<member><command>step</command></member>
<member><command>s</command></member>
</simplelist>
</msgtext>
</entry>
<entry>
continue execution until next 'C' line of code
(enters function call)
</entry>
</row>
<row>
<entry>
<msgtext>
<simplelist type="inline">
<member><command>next</command></member>
<member><command>n</command></member>
</simplelist>
</msgtext>
</entry>
<entry>
continue execution until next 'C' line of code
(doesn't enter function call)
</entry>
</row>
<row>
<entry>
<msgtext>
<simplelist type="inline">
<member><command>stepi</command></member>
<member><command>si</command></member>
</simplelist>
</msgtext>
</entry>
<entry>
execute next assembly instruction (enters function
call)
</entry>
</row>
<row>
<entry>
<msgtext>
<simplelist type="inline">
<member><command>nexti</command></member>
<member><command>ni</command></member>
</simplelist>
</msgtext>
</entry>
<entry>
execute next assembly instruction (doesn't enter
function call)
</entry>
</row>
<row>
<entry>
<msgtext>
<simplelist type="inline">
<member><command>finish</command></member>
<member><command>f</command></member>
</simplelist>
</msgtext>
</entry>
<entry>execute until current function is exited</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
<para>
<command>cont</command>, <command>step</command>,
<command>next</command>, <command>stepi</command>,
<command>nexti</command> can be postfixed by a number (N),
meaning that the command must be executed N times.
</para>
</sect2>
<sect2>
<title>Breakpoints, watch points</title>
<para>
<table>
<title>WineDbg's break & watch points</title>
<tgroup cols="2" align="left">
<tbody>
<row>
<entry><command>enable&nbsp;N</command></entry>
<entry>enables (break|watch)point #N</entry>
</row>
<row>
<entry><command>disable&nbsp;N</command></entry>
<entry>disables (break|watch)point #N</entry>
</row>
<row>
<entry><command>delete&nbsp;N</command></entry>
<entry>deletes (break|watch)point #N</entry>
</row>
<row>
<entry><command>cond&nbsp;N</command></entry>
<entry>
removes any existing condition to
(break|watch)point N
</entry>
</row>
<row>
<entry>
<command>cond&nbsp;N &lt;expr&gt;</command>
</entry>
<entry>
adds condition &lt;expr&gt; to (break|watch)point
N. &lt;expr&gt; will be evaluated each time the
breakpoint is hit. If the result is a zero value,
the breakpoint isn't triggered
</entry>
</row>
<row>
<entry><command>break&nbsp;*&nbsp;N</command></entry>
<entry>adds a breakpoint at address N</entry>
</row>
<row>
<entry><command>break &lt;id&gt;</command></entry>
<entry>
adds a breakpoint at the address of symbol
&lt;id&gt;
</entry>
</row>
<row>
<entry><command>break &lt;id&gt;&nbsp;N</command></entry>
<entry>
adds a breakpoint at the address of symbol
&lt;id&gt; (N ?)
</entry>
</row>
<row>
<entry><command>break&nbsp;N</command></entry>
<entry>
adds a breakpoint at line N of current source file
</entry>
</row>
<row>
<entry><command>break</command></entry>
<entry>
adds a breakpoint at current $PC address
</entry>
</row>
<row>
<entry><command>watch&nbsp;*&nbsp;N</command></entry>
<entry>
adds a watch command (on write) at address N (on 4
bytes)
</entry>
</row>
<row>
<entry><command>watch &lt;id&gt;</command></entry>
<entry>
adds a watch command (on write) at the address of
symbol &lt;id&gt;
</entry>
</row>
<row>
<entry><command>info break</command></entry>
<entry>
lists all (break|watch)points (with state)
</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
<para>
You can use the symbol <emphasis>EntryPoint</emphasis> to stand for
the entry point of the Dll.
</para>
<para>
When setting a break/watch-point by &lt;id&gt;, if the
symbol cannot be found (for example, the symbol is contained
in a not yet loaded module), winedbg will recall the name of
the symbol and will try to set the breakpoint each time a
new module is loaded (until it succeeds).
</para>
</sect2>
<sect2>
<title>Stack manipulation</title>
<para>
<table>
<title>WineDbg's stack manipulation</title>
<tgroup cols="2" align="left">
<tbody>
<row>
<entry><command>bt</command></entry>
<entry>print calling stack of current thread</entry>
</row>
<row>
<entry><command>bt&nbsp;N</command></entry>
<entry>
print calling stack of thread of ID N (note: this
doesn't change the position of the current frame
as manipulated by the <command>up</command> and
<command>dn</command> commands)
</entry>
</row>
<row>
<entry><command>up</command></entry>
<entry>
goes up one frame in current thread's stack
</entry>
</row>
<row>
<entry><command>up&nbsp;N</command></entry>
<entry>
goes up N frames in current thread's stack
</entry>
</row>
<row>
<entry><command>dn</command></entry>
<entry>
goes down one frame in current thread's stack
</entry>
</row>
<row>
<entry><command>dn&nbsp;N</command></entry>
<entry>
goes down N frames in current thread's stack
</entry>
</row>
<row>
<entry><command>frame&nbsp;N</command></entry>
<entry>
set N as the current frame for current thread's
stack
</entry>
</row>
<row>
<entry><command>info&nbsp;local</command></entry>
<entry>
prints information on local variables for current
function frame
</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
</sect2>
<sect2>
<title>Directory & source file manipulation</title>
<para>
<table>
<title>WineDbg's directory & source file manipulation</title>
<tgroup cols="2" align="left">
<tbody>
<row>
<entry><command>show&nbsp;dir</command></entry>
<entry>
prints the list of dir:s where source files are
looked for
</entry>
</row>
<row>
<entry>
<command>dir&nbsp;&lt;pathname&gt;</command>
</entry>
<entry>
adds &lt;pathname&gt; to the list of dir:s
where to look for source files
</entry>
</row>
<row>
<entry><command>dir</command></entry>
<entry>
deletes the list of dir:s where to look for source
files
</entry>
</row>
<row>
<entry>
<command>
symbolfile&nbsp;&lt;pathname&gt;
</command>
</entry>
<entry>loads external symbol definition</entry>
</row>
<row>
<entry>
<command>
symbolfile&nbsp;&lt;pathname&gt;&nbsp;N
</command>
</entry>
<entry>
loads external symbol definition (applying an
offset of N to addresses)
</entry>
</row>
<row>
<entry><command>list</command></entry>
<entry>
lists 10 source lines forwards from current
position
</entry>
</row>
<row>
<entry><command>list&nbsp;-</command></entry>
<entry>
lists 10 source lines backwards from current
position
</entry>
</row>
<row>
<entry><command>list&nbsp;N</command></entry>
<entry>
lists 10 source lines from line N in current file
</entry>
</row>
<row>
<entry>
<command>list&nbsp;&lt;path&gt;:N</command>
</entry>
<entry>
lists 10 source lines from line N in file
&lt;path&gt;
</entry>
</row>
<row>
<entry><command>list &lt;id&gt;</command></entry>
<entry>
lists 10 source lines of function &lt;id&gt;
</entry>
</row>
<row>
<entry><command>list&nbsp;*&nbsp;N</command></entry>
<entry>lists 10 source lines from address N</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
<para>
You can specify the end target (to change the 10 lines
value) using the ','. For example:
<table>
<title>WineDbg's list command examples</title>
<tgroup cols="2" align="left">
<tbody>
<row>
<entry><command>list 123, 234</command></entry>
<entry>
lists source lines from line 123 up to line 234 in
current file
</entry>
</row>
<row>
<entry><command>list foo.c:1,&nbsp;56</command></entry>
<entry>
lists source lines from line 1 up to 56 in file
foo.c
</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
</sect2>
<sect2>
<title>Displaying</title>
<para>
A display is an expression that's evaluated and printed
after the execution of any <command>winedbg</command>
command.
</para>
<para>
<command>winedbg</command> will automatically detect if the
expression you entered contains a local variable. If so,
display will only be shown if the context is still in the
same function as the one the debugger was in when the
display expression was entered.
</para>
<para>
<table>
<title>WineDbg's displays</title>
<tgroup cols="2" align="left">
<tbody>
<row>
<entry>
<command>info&nbsp;display</command>
</entry>
<entry>lists the active displays</entry>
</row>
<row>
<entry>
<command>display</command>
</entry>
<entry>
print the active displays' values (as done each
time the debugger stops)
</entry>
</row>
<row>
<entry>
<command>display&nbsp;&lt;expr&gt;</command>
</entry>
<entry>
adds a display for expression &lt;expr&gt;
</entry>
</row>
<row>
<entry>
<command>
display&nbsp;/fmt&nbsp;&lt;expr&gt;
</command>
</entry>
<entry>
adds a display for expression
&lt;expr&gt;. Printing evaluated &lt;expr&gt; is
done using the given format (see
<command>print</command> command for more on
formats)
</entry>
</row>
<row>
<entry>
<msgtext>
<simplelist type="inline">
<member>
<command>del&nbsp;display&nbsp;N</command>
</member>
<member>
<command>undisplay&nbsp;N</command>
</member>
</simplelist>
</msgtext>
</entry>
<entry>deletes display #N</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
</sect2>
<sect2>
<title>Disassembly</title>
<para>
<table>
<title>WineDbg's dissassembly</title>
<tgroup cols="2" align="left">
<tbody>
<row>
<entry><command>disas</command></entry>
<entry>disassemble from current position</entry>
</row>
<row>
<entry>
<command>disas&nbsp;&lt;expr&gt;</command>
</entry>
<entry>
disassemble from address &lt;expr&gt;
</entry>
</row>
<row>
<entry>
<command>
disas&nbsp;&lt;expr&gt;,&lt;expr&gt;
</command>
</entry>
<entry>
disassembles code between addresses specified by
the two &lt;expr&gt;
</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
</sect2>
<sect2>
<title>Memory (reading, writing, typing)</title>
<para>
<table>
<title>WineDbg's memory management</title>
<tgroup cols="2" align="left">
<tbody>
<row>
<entry>
<command>x&nbsp;&lt;expr&gt;</command>
</entry>
<entry>
examines memory at &lt;expr&gt; address
</entry>
</row>
<row>
<entry>
<command>
x&nbsp;/fmt&nbsp;&lt;expr&gt;
</command>
</entry>
<entry>
examines memory at &lt;expr&gt; address using
format /fmt
</entry>
</row>
<row>
<entry>
<command>
print&nbsp;&lt;expr&gt;
</command>
</entry>
<entry>
prints the value of &lt;expr&gt; (possibly using
its type)
</entry>
</row>
<row>
<entry>
<command>
print&nbsp;/fmt&nbsp;&lt;expr&gt;
</command>
</entry>
<entry>prints the value of &lt;expr&gt; (possibly
using its type)
</entry>
</row>
<row>
<entry>
<command>
set&nbsp;&lt;lval&gt;&nbsp;=&nbsp;&lt;expr&gt;
</command>
</entry>
<entry>
writes the value of &lt;expr&gt; in &lt;lval&gt;
</entry>
</row>
<row>
<entry>
<command>
whatis&nbsp;&lt;expr&gt;
</command>
</entry>
<entry>
prints the C type of expression &lt;expr&gt;
</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
<para>
<filename>/fmt</filename> is either <filename>/&lt;letter&gt;</filename> or
<filename>/&lt;count&gt;&lt;letter&gt;</filename> letter can be
<simplelist type="horiz" columns="2">
<member>s</member><member>an ASCII string</member>
<member>u</member><member>an Unicode UTF16 string</member>
<member>i</member><member>instructions (disassemble)</member>
<member>x</member><member>32 bit unsigned hexadecimal integer</member>
<member>d</member><member>32 bit signed decimal integer</member>
<member>w</member><member>16 bit unsigned hexadecimal integer</member>
<member>c</member><member>character (only printable 0x20-0x7f are actually printed)</member>
<member>b</member><member>8 bit unsigned hexadecimal integer</member>
<member>g</member><member>GUID</member>
</simplelist>
</para>
</sect2>
<sect2>
<title>Information on Wine's internals</title>
<para>
<table>
<title>WineDbg's Win32 objects management</title>
<tgroup cols="2" align="left">
<tbody>
<row>
<entry><command>info&nbsp;class</command></entry>
<entry>
lists all Windows' classes registered in Wine
</entry>
</row>
<row>
<entry>
<command>
info&nbsp;class&nbsp;&lt;id&gt;
</command>
</entry>
<entry>
prints information on Windows's class &lt;id&gt;
</entry>
</row>
<row>
<entry><command>info&nbsp;share</command></entry>
<entry>
lists all the dynamic libraries loaded in the
debugged program (including .so files, NE and PE
DLLs)
</entry>
</row>
<row>
<entry>
<command>
info&nbsp;share&nbsp;&lt;N&gt;
</command>
</entry>
<entry>
prints information on module at address &lt;N&gt;
</entry>
</row>
<row>
<entry><command>info regs</command></entry>
<entry>
prints the value of the CPU registers
</entry>
</row>
<row>
<entry>
<command>info segment &lt;N&gt;</command>
</entry>
<entry>
prints information on segment &lt;N&gt; (i386
only)
</entry>
</row>
<row>
<entry>
<command>info&nbsp;segment</command>
</entry>
<entry>
lists all allocated segments (i386 only)
</entry>
</row>
<row>
<entry><command>info&nbsp;stack</command></entry>
<entry>
prints the values on top of the stack
</entry>
</row>
<row>
<entry><command>info&nbsp;map</command></entry>
<entry>
lists all virtual mappings used by the debugged
program
</entry>
</row>
<row>
<entry>
<command>info&nbsp;map&nbsp;&lt;N&gt</command>
</entry>
<entry>
lists all virtual mappings used by the program of
pid &lt;N&gt;
</entry>
</row>
<row>
<entry>
<command>info&nbsp;wnd&nbsp;&lt;N&gt</command>
</entry>
<entry>
prints information of Window of handle &lt;N&gt;
</entry>
</row>
<row>
<entry><command>info&nbsp;wnd</command></entry>
<entry>
lists all the window hierarchy starting from the
desktop window
</entry>
</row>
<row>
<entry><command>info process</command></entry>
<entry>
lists all w-processes in Wine session
</entry>
</row>
<row>
<entry><command>info&nbsp;thread</command></entry>
<entry>lists all w-threads in Wine session</entry>
</row>
<row>
<entry><command>info&nbsp;exception</command></entry>
<entry>
lists the exception frames (starting from current
stack frame)
</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
</sect2>
<sect2 id="winedbg-dbg-chan">
<title>Debug channels</title>
<para>
It is possible to turn on and off debug messages as you
are debugging using the set command.
See <xref linkend="debugging"> for more details on debug
channels.
</para>
<para>
<table>
<title>WineDbg's debug channels' management</title>
<tgroup cols="2" align="left">
<tbody>
<row>
<entry>
<command>set&nbsp;+&nbsp;warn&nbsp;win</command>
</entry>
<entry>turn on warn on 'win' channel</entry>
</row>
<row>
<entry>
<command>set&nbsp;+&nbsp;win</command>
</entry>
<entry>
turn on warn/fixme/err/trace on 'win' channel
</entry>
</row>
<row>
<entry>
<command>set&nbsp;-&nbsp;win</command>
</entry>
<entry>
turn off warn/fixme/err/trace on 'win' channel
</entry>
</row>
<row>
<entry>
<command>set&nbsp;-&nbsp;fixme</command>
</entry>
<entry>turn off the 'fixme' class</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
</sect2>
</sect1>
<sect1 id="dbg-others">
<title>Other debuggers</title>
<sect2>
<title>GDB mode</title>
<para>
WineDbg can act as a remote monitor for GDB. This allows to
use all the power of GDB, but while debugging wine and/or
any Win32 application. To enable this mode, just add
<parameter>--gdb</parameter> to winedbg command line. You'll
end up on a GDB prompt. You'll have to use the GDB commands
(not WineDbg's).
</para>
<para>
However, some limitation in GDB while debugging wine (see
below) don't appear in this mode:
<itemizedlist>
<listitem>
<para>
GDB will correctly present Win32 thread
information and breakpoint behavior
</para>
</listitem>
<listitem>
<para>
Moreover, it also provides support for the Dwarf II
debug format (which became the default format (instead
of stabs) in gcc 3.1).
</para>
</listitem>
</itemizedlist>
</para>
<para>
A few Wine extensions available through the monitor command.
<table>
<title>WineDbg's debug channels' management</title>
<tgroup cols="2" align="left">
<tbody>
<row>
<entry><command>monitor&nbsp;wnd</command></entry>
<entry>lists all window in the Wine session</entry>
</row>
<row>
<entry><command>monitor&nbsp;proc</command></entry>
<entry>
lists all processes in the Wine session
</entry>
</row>
<row>
<entry><command>monitor&nbsp;mem</command></entry>
<entry>
displays memory mapping of debugged process
</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
</sect2>
<sect2>
<title>Graphical frontends to gdb</title>
<para>
This section will describe how you can debug Wine using the
GDB mode of winedbg and some graphical front ends to GDB for
those of you who really like graphical debuggers.
</para>
<sect3>
<title>DDD</title>
<para>
Use the following steps, in this order:
<orderedlist>
<listitem>
<para>
Start the Wine debugger with a command line like:
<screen>
winedbg --gdb --no-start &lt;name_of_exe_to_debug.exe&gt;
</screen>
</para>
</listitem>
<listitem>
<para>
Start ddd
</para>
</listitem>
<listitem>
<para>
In ddd, use the 'Open File' or 'Open Program' to
point to the Wine executable (which is either
wine-pthread or wine-kthread depending on your
settings).
</para>
</listitem>
<listitem>
<para>
In the output of 1/, there's a line like
<screen>
target remote localhost:32878
</screen>
copy that line and paste into ddd command pane (the
one with the (gdb) prompt)
</para>
</listitem>
</orderedlist>
The program should now be loaded and up and running. If
you want, you can also add in 1/ after the name of the
exec all the needed parameters
</para>
</sect3>
<sect3>
<title>kdbg</title>
<para>
Use the following steps, in this order:
<orderedlist>
<listitem>
<para>
Start the Wine debugger with a command line like:
<screen>
winedbg --gdb --no-start &lt;name_of_exe_to_debug.exe&gt;
</screen>
</para>
</listitem>
<listitem>
<para>
In the output of 1/, there's a line like
<screen>
target remote localhost:32878
</screen>
Start kdbg with
<screen>
kdbg -r localhost:32878 wine
</screen>
localhost:32878 is not a fixed value, but has been
printed in step 1/. 'wine' should also be the full
path to the Wine executable (which is either
wine-pthread or wine-kthread depending on your settings).
</para>
</listitem>
</orderedlist>
The program should now be loaded and up and running. If
you want, you can also add in 1/ after the name of the
exec all the needed parameters
</para>
</sect3>
</sect2>
<sect2>
<title>Using other Unix debuggers</title>
<para>
You can also use other debuggers (like
<command>gdb</command>), but you must be aware of a few
items:
</para>
<para>
You need to attach the unix debugger to the correct unix
process (representing the correct windows thread) (you can
"guess" it from a <command>ps fax</command> for example:
When running the emulator, usually the first two
<varname>upids</varname> are for the Windows' application
running the desktop, the first thread of the application is
generally the third <varname>upid</varname>; when running a
Winelib program, the first thread of the application is
generally the first <varname>upid</varname>)
</para>
<note>
<para>
If you plan to used <command>gdb</command> for a
multi-threaded Wine application (native or Winelib), then
<command>gdb</command> will be able to handle the multiple
threads directly only if:
<itemizedlist>
<listitem>
<para>
Wine is running on the pthread model (it won't work
in the kthread one). See the Wine architecture
documentation for further details.
</para>
</listitem>
<listitem>
<para>
<command>gdb</command> supports the multi-threading
(you need gdb at least 5.0 for that).
</para>
</listitem>
</itemizedlist>
In the unfortunate case (no direct thread support in
<command>gdb</command> because one of the above conditions
is false), you'll have to spawn a different
<command>gdb</command> session for each Windows' thread
you wish to debug (which means no synchronization for
debugging purposes between the various threads).
</para>
</note>
<para>
Here's how to get info about the current execution status of a
certain Wine process:
</para>
<para>
Change into your Wine source dir and enter:
</para>
<screen>
$ gdb wine
</screen>
<para>
Switch to another console and enter <command>ps ax | grep
wine</command> to find all wine processes. Inside
<command>gdb</command>, repeat for all Wine processes:
</para>
<screen>
(gdb) attach <userinput>PID</userinput>
</screen>
<para>
with <userinput>PID</userinput> being the process ID of one of
the Wine processes. Use
</para>
<screen>
(gdb) bt
</screen>
<para>
to get the backtrace of the current Wine process, i.e. the
function call history. That way you can find out what the
current process is doing right now. And then you can use
several times:
</para>
<screen>
(gdb) n
</screen>
<para>
or maybe even
</para>
<screen>
(gdb) b <userinput>SomeFunction</userinput>
</screen>
<para>
and
</para>
<screen>
(gdb) c
</screen>
<para>
to set a breakpoint at a certain function and continue up to
that function. Finally you can enter
</para>
<screen>
(gdb) detach
</screen>
<para>
to detach from the Wine process.
</para>
<!-- *** End of xtra content *** -->
</sect2>
<sect2>
<title>Using other Windows debuggers</title>
<para>
You can use any Windows' debugging API compliant debugger
with Wine. Some reports have been made of success with
VisualStudio debugger (in remote mode, only the hub runs
in Wine). GoVest fully runs in Wine.
</para>
</sect2>
<sect2>
<title>Main differences between winedbg and regular Unix debuggers</title>
<table><title>Debuggers comparison</title>
<tgroup cols=2 align="left">
<tbody>
<row>
<entry>WineDbg</entry><entry>gdb</entry>
</row>
<row>
<entry>
WineDbg debugs a Windows' process: the various
threads will be handled by the same WineDbg session,
and a breakpoint will be triggered for any thread of
the W-process
</entry>
<entry>
gdb debugs a Windows' thread: a separate gdb session
is needed for each thread of a Windows' process and
a breakpoint will be triggered only for the w-thread
debugged
</entry>
</row>
<row>
<entry>
WineDbg supports debug information from stabs
(standard Unix format) and Microsoft's C, CodeView,
.DBG
</entry>
<entry>
GDB supports debug information from stabs (standard
Unix format) and Dwarf II.
</entry>
</row>
</tbody>
</tgroup>
</table>
</sect2>
</sect1>
</chapter>
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