Sweden-Number/documentation/debugging

This file describes where to start debugging Wine and how to write
useful bug reports.

Crashes
=======

  These usually show up like this:

|Unexpected Windows program segfault - opcode = 8b
|Segmentation fault in Windows program 1b7:c41.
|Reading symbols from file /root/wine/wine.sym
|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

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 newsgroup or the
relevant developer as feasonable.
  
 1. 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 segmentregister from the stack or the like. When reporting a
    crash, report this WHOLE crashdump even if it doesn't make sense to you.

    (In this case it is access to an invalid selector, for %es is 0000, as
    seen in the register dump).
    
 2. Determine where the reason came from.
    Since this is usually a primary/secondary reaction to a failed or
    misbehaving Wine function, rerun Wine with "-debugmsg +relay" (without ")
    added to the commandline. This will get rather much output, but usually
    the reason is located in the last call(s).  Those lines usually look like
    this:

|Call KERNEL.90: LSTRLEN(0227:0692) ret=01e7:2ce7 ds=0227
      ^^^^^^^^^  ^       ^^^^^^^^^      ^^^^^^^^^    ^^^^
      |          |       |              |            |Datasegment on entry
      |          |       |              |Return address.
      |          |       |
      |          |       |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=0x0007 ret=01e7:2ce7 ds=0227
                                  ^^^^^^
				  |Returnvalue is 16 bit and has the value 7.


 3. 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
    "dprintf_xyz(stddeb,"Fnction(...)"...);" at the beginning of the
    function. Rerun wine with "-debugmsg +xyz,+relay" added to the
    commandline.

 4. If the crash happened in a function in WINE, find out the exact line using
    gdb (the sample crash has another reason):
|... somewhere in the backtrace ...
|5 0x080e5ad8 (CreateWindowEx32A+0xd8)
|...
|$ gdb wine
|...
|(gdb) l *0x080e5ad8
|0x80e5ad8 is in CreateWindowEx32A (win.c:837).
|...
|837         return WIN_CreateWindowEx( &cs, classAtom, FALSE );
|...


 5. If those information isn't clear enough or if you want to know more about
    what's happening in the function itself, try running wine with "-debugmsg
    +all", which dumps ALL included debug information in wine.

 6. If that isn't enough add more debug output for yourself into the
    functions you find relevant.
    You might also try to run the program in gdb instead of using the
    WINE-debugger.
  
 7. You can also set a breakpoint for that function. Start wine with the
    "-debug" option added to the commandline. After loading the executable
    wine will enter the internal debugger. Use "break KERNEL.LSTRLEN"
    (replace by function you want to debug, CASE IS RELEVANT.) to set a
    breakpoint.  Then use "continue" 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 "continue" 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.


Program hangs, nothing happens
==============================

  Switch to UNIX shell, get the process-ID using "ps -a|grep wine", and do a
  "kill -HUP <pid>" (without " and <>). Wine will then enter its internal
  debugger and you can proceed as explained above.

Program reports an error with a Messagebox
==========================================

  Sometimes programs are reporting failure using a 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.

  Since the failure happens usually directly before setting up the Messagebox
  you can start wine with "-debug" added to the commandline, set a breakpoint
  at "USER.MESSAGEBOX" (win16 programs) "USER32.MessageBox" (win32 Programs)
  and proceed with "continue". With "-debugmsg +all" Wine will now stop
  directly directly before setting up the Messagebox.  Proceed as explained
  above.


Disassembling programs:
=======================
  You may also try to disassemble the offending program to check for 
  undocumented features and/or use of them.
  The best, freely available, disassembler for win16 programs is
  Windows Codeback, archivename wcbxxx.zip, which usually can be found
  in the Cica-Mirror subdirectory on the WINE ftpsites. (See ANNOUNCE).
  Disassembling win32 programs is currenty only possible using 
  Windows Disassembler 32, archivename something like wdasm32x.zip on
  ftp.winsite.com and mirrors.
  Understanding disassembled code is just a question of exercise.
  Most code out there uses standard C function entries (for it is usually 
  written in C). Win16 function entries usually look like that:
|  	push bp
|	mov bp, sp
|	... function code ..
|	retf XXXX 	<--------- XXXX is number of bytes of arguments

  This is a FAR function with no local storage. The arguments usually start
  at [bp+6] with increasing offsets. Note, that [bp+6] belongs to the RIGHTMOST 
  argument, for exported win16 functions use the PASCAL calling convention.
  So, if we use strcmp(a,b) with a and b both 32 bit variables b would be at
  [bp+6] and a at [bp+10].
  Most functions make also use of local storage in the stackframe:
|	enter 0086, 00
|	... function code ...
|	leave
|	retf XXXX
  This does mostly the same as above, but also adds 0x86 bytes of
  stackstorage, which is accessed using [bp-xx].
  Before calling a function, arguments are pushed on the stack using something
  like this:
|	push word ptr [bp-02]	<- will be at [bp+8]
|	push di			<- will be at [bp+6]
|	call KERNEL.LSTRLEN
  Here first the selector and then the offset to the passed string are pushed.


Sample debugging session:
=========================

  Let's debug the infamous Word SHARE.EXE messagebox: 

|marcus@jet $ wine winword.exe
|            +---------------------------------------------+
|            | !  You must leave Windows and load SHARE.EXE|
|            |    before starting Word.                    |
|            +---------------------------------------------+


|marcus@jet $ wine winword.exe -debugmsg +relay -debug
|CallTo32(func=08007e00,000001c4,00000081,00000000,00000000)
|CallTo32(func=08007e00,000001c4,00000014,000006d0,00000000)
|Win16 task 'winword': Breakpoint 1 at 0x0157:0x001a
|CallTo16(func=0097:0130,ds=0000)
|Call WPROCS.24: TASK_RESCHEDULE() ret=003f:0759 ds=0000
|Ret  WPROCS.24: TASK_RESCHEDULE() retval=0x0000 ret=003f:0759 ds=08a7
|CallTo16(func=0157:001a,ds=08a7,0x11d7,0x0000,0x0000,0x3cb4,0x1f40,0x0000,0x0000,0x08a7)
|Reading symbols from file /root/wine/wine.sym
|Stopped on breakpoint 1 at 0x0157:0x001a
|In 16 bit mode.
|0x0157:0x001a:  xorw	%bp,%bp
|Wine-dbg> break USER.MESSAGEBOX                       <---- Set Breakpoint
|Breakpoint 2 at 0x0067:0x00000000 (USER.MESSAGEBOX)
|Wine-dbg>c                                            <---- 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)
|...                                                   <----- Much debugoutput
|Call KERNEL.97: GETTEMPFILENAME(0x00c3,08a7:8350,0x0000,08a7:8234) ret=058f:09b1 ds=08a7
                                 ^      ^         ^      ^
				 |      |         |      |LPSTR buffer
				 |      |         |UINT16 unique
				 |      |LPCSTR prefix
				 |BYTE drive

|Ret  KERNEL.97: GETTEMPFILENAME() retval=0xce3f ret=058f:09b1 ds=08a7
                                          ^
                                          |new unique number

|Call KERNEL.74: OPENFILE(08a7:8234,08a7:82c6,0x1012) ret=058f:09d8 ds=08a7
                          ^         ^         ^
                          |         |         |UINT32 mode
                          |         |OFSTRUCT *ofs
                          |LPCSTR name

|Ret  KERNEL.74: OPENFILE() retval=0xffff ret=058f:09d8 ds=08a7
                                   ^
				   | -1 aka. HFILE_ERROR

|Stopped on breakpoint 2 at 0x0067:0x00000000 (USER.MESSAGEBOX)
|In 32 bit mode.
|0x0067:0x00000000 (USER.MESSAGEBOX):  pushw	%bp

    Now, we see that OPENFILE seem to have returned 0xFFFF (or -1). Checking
    the implementation of OpenFile in files/file.c, this signals an error.
    The mode flags (OF_READWRITE|OF_SHARE_EXCLUSIVE|OF_CREATE) seems to
    indicate, that WinWord wants to open the file for writing, so we check
    the filename. Since we don't see the filename in this debugoutput, we use
    the dprintf_file() in OpenFile to print out more information by adding
    "-debugmsg +relay" to the commandline.

    (In fact, we see that the filename has been returned by the GetTempFileName
     function above, but we check it anyway.)

|marcus@jet $ wine winword.exe -debugmsg +relay,+file -debug
|.....much more debugoutput .....
|
|Call KERNEL.97: GETTEMPFILENAME(0x00c3,08a7:8350,0x0000,08a7:8234) ret=058f:09b1 ds=08a7
|FILE_Create: 'C:~docd03d.tmp' 01b6 1
|FILE_SetDosError: errno = 13
|GetTempFileName: returning C:\~DOCD03D.TMP
|Ret  KERNEL.97: GETTEMPFILENAME() retval=0xd03d ret=058f:09b1 ds=08a7
|Call KERNEL.74: OPENFILE(08a7:8234,08a7:82c6,0x1012) ret=058f:09d8 ds=08a7
|OpenFile: C:\~DOCD03D.TMP 1012
|FILE_AllocTaskHandle: returning task handle 1, dos_file 0, file 1 of 254
|FILE_Create: 'C:\~DOCD03D.TMP' 01b6 0
|FILE_SetDosError: errno = 13
|OpenFile(C:\~DOCD03D.TMP): return = HFILE_ERROR
|FILE_FreeTaskHandle: dos=1 file=0
|Ret  KERNEL.74: OPENFILE() retval=0xffff ret=058f:09d8 ds=08a7

    The filename is "C:\~DOCD03D.TMP". Of course, C:\ is writeable for the
    superuser only, so the open fails for a normal user and OpenFile returns
    -1, which in turn generates this messagebox.


Written by Marcus Meissner <msmeissn@cip.informatik.uni-erlangen.de>,
additions welcome.