Written by &name-eric-pouech; &email-eric-pouech; (Last updated: 6/14/2000) (Extracted from wine/documentation/winedbg) 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. Each Windows' thread is implemented as a Unix process (under Linux using the clone syscall), meaning that all threads of a same Windows' process share the same (unix) address space. In the following: W-process means a process in Windows' terminology U-process means a process in Unix' terminology W-thread means a thread in Windows' terminology A W-process is made of one or several W-threads. Each W-thread is mapped to one and only one U-process. All U-processes of a same W-process share the same address space. Each Unix process can be identified by two values: the Unix process id (upid in the following) the Windows's thread id (tid) Each Windows' process has also a Windows' process id (wpid in the following). It must be clear that upid and wpid are different and shall not be used instead of the other. Wpid and tid 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 W-process). When talking of debugging in Wine, there are at least two levels to think of: the Windows' debugging API. the Wine integrated debugger, dubbed WineDbg. Wine implements most of the Windows' debugging API (the part in KERNEL32, not the one in IMAGEHLP.DLL), and allows any program (emulated or Winelib) using that API to debug a W-process. WineDbg is a Winelib application making use of this API to allow debugging both any Wine or Winelib applications as well as Wine itself (kernel and all DLLs). Any application (either a Windows' native executable, or a Winelib application) can be run through WineDbg. Command line options and tricks are the same as for wine: winedbg telnet.exe winedbg "hl.exe -windowed" WineDbg can also be launched without any command line argument: WineDbg is started without any attached process. You can get a list of running W-processes (and their wpid's) using the walk process command, and then, with the attach command, pick up the wpid of the W-process you want to debug. This is (for now) a neat feature for the following reasons: you can debug an already started application When something goes wrong, Windows tracks this as an exception. Exceptions exist for segmentation violation, stack overflow, division by zero... When an exception occurs, Wine checks if the W-process 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. If the W-process is not debugged, Wine tries to launch a debugger. This debugger (normally WineDbg, see III Configuration for more details), at startup, attaches to the W-process 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. If WineDbg is the standard debugger, the pass and cont commands are the two ways to let the process go further for the handling of the exception event. 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: continue: the debugger had the ability to correct what's generated the exception, and is now able to continue process execution. pass: 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. since some of Wine's code uses exceptions and try/catch blocks to provide some functionality, WineDbg can be entered in such cases with segv exceptions. This happens, for example, with IsBadReadPtr function. In that case, the pass command shall be used, to let the handling of the exception to be done by the catch block in IsBadReadPtr. Unfortunately, Windows doesn't provide a detach kind of API, meaning that once you started debugging a process, you must do so until the process dies. Killing (or stopping/aborting) the debugger will also kill the debugged process. This will be true for any Windows' debugging API compliant debugger, starting with WineDbg. Written by &name-marcus-meissner; &email-marcus-meissner;, additions welcome. (Extracted from wine/documentation/debugging) This file describes where to start debugging Wine. If at any point you get stuck and want to ask for help, please read the file documentation/bugreports for information on how to write useful bug reports. These usually show up like this: |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 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 feasible. 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). Determine the cause of the crash. Since this is usually a primary/secondary reaction to a failed or misbehaving Wine function, rerun Wine with -debugmsg +relay added to the commandline. 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: |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. 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 TRACE(<channel>,"(...)\n"); at the beginning of the function. Rerun wine with -debugmsg +xyz,+relay added to the commandline. Additional information on how to debug using the internal debugger can be found in debugger/README. 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 -debugmsg +all, which dumps ALL included debug information in wine. If even that isn't enough, add more debug output for yourself into the functions you find relevant. See documentation/debug-msgs. You might also try to run the program in gdb instead of using the WINE-debugger. If you do that, use handle SIGSEGV nostop noprint to disable the handling of seg faults inside gdb (needed for Win16). If you don't use the --desktop or --managed option, start the WINE process with --sync, or chances are good to get X into an unusable state. 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. Switch to UNIX shell, get the process-ID using ps -a | grep wine, and do a kill -HUP <pid> (without the < and >). Wine will then enter its internal debugger and you can proceed as explained above. Also, you can use --debug switch and then you can get into internal debugger by pressing CtrlC in the terminal where you run Wine. 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. 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 MessageBoxA (called by win16 and win32 programs) and proceed with continue. With --debugmsg +all Wine will now stop directly before setting up the Messagebox. Proceed as explained above. You can also run wine using wine -debugmsg +relay program.exe 2>&1 | less -i and in less search for MessageBox. 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 possible using Windows Disassembler 32, archivename something like w32dsm87.zip (or similar) on ftp.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) Interactive Disassembler (IDA) from the ftp sites mentioned at the end of the document. Understanding disassembled code is mostly 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. 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(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 <---- Set Breakpoint |Breakpoint 2 at 0x40189100 (MessageBoxA [msgbox.c:190]) |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.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. Whoops, it even detects that something is wrong! |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 This fails, since my C: drive is in this case mounted readonly. |Ret KERNEL.74: OPENFILE() retval=0xffff ret=060f:09d8 ds=0927 ^^^^^^ HFILE_ERROR16, yes, it failed. |Call USER.1: MESSAGEBOX(0x0000,0x09278376"Sie mussen Windows verlassen und SHARE.EXE laden bevor Sie Word starten.",0x00000000,0x1030) ret=060f:084f ds=0927 And MessageBox'ed. |Stopped on breakpoint 2 at 0x40189100 (MessageBoxA [msgbox.c:190]) |190 { <- the sourceline In 32 bit mode. Wine-dbg> The code seems to find a writeable harddisk and tries to create a file there. To work around this bug, you can define C: as a networkdrive, which is ignored by the code above. Here are some useful debugging tips, added by Andreas Mohr: 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 wine --debugmsg +relay program to get a listing of the functions the program calls in its start function. Now you do a wine --debug winfile.exe This way, you get into Wine-dbg. Now you can set a breakpoint on any function the program calls in the start function and just type c 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. 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 MessageBox(). That's why you should re-run the program with e.g. wine --debugmsg +relay <program name> &>relmsg Then do a more relmsg and search for the last occurrence of a call to the string "MESSAGEBOX". This is a line like Call USER.1: MESSAGEBOX(0x0000,0x01ff1246 "Runtime error 219 at 0004:1056.",0x00000000,0x1010) ret=01f7:2160 ds=01ff In my example the lines before the call to MessageBox() look like that: 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 I think that the call to MessageBox() in this example is not 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 0x0004:0x1056. As the segment value of the address is only 4, I think that that is only an internal program value. But the offset address reveals something quite interesting: Offset 1056 is very close to the return address of FREELIBRARY(): Call KERNEL.96: FREELIBRARY(0x031f) ret=01cf:105c ds=01ff ^^^^ Provided that segment 0x0004 is indeed segment 0x1cf, we now we can use IDA (available at ftp://ftp.uni-koeln.de/pc/msdos/programming/assembler/ida35bx.zip) to disassemble the part that caused the error. We just have to find the address of the call to FreeLibrary(). 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 0x1cf). 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 GetVersion16/32 as those functions are called very often. Then do a c until you are able to set this breakpoint without error message. Some useful programs: IDA: ftp://ftp.uni-koeln.de/pc/msdos/programming/assembler/ida35bx.zip Very good DOS disassembler ! It's badly needed for debugging Wine sometimes. XRAY: ftp://ftp.th-darmstadt.de/pub/machines/ms-dos/SimTel/msdos/asmutil/xray15.zip Traces DOS calls (Int 21h, DPMI, ...). Use it with Windows to correct file management problems etc. pedump: http://oak.oakland.edu/pub/simtelnet/win95/prog/pedump.zip Dumps the imports and exports of a PE (Portable Executable) DLL. After starting your program with wine -debug myprog.exe the program loads and you get a prompt at the program starting point. Then you can set breakpoints: b RoutineName (by outine name) OR b *0x812575 (by address) Then you hit c (continue) to run the program. It stops at the breakpoint. You can type 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 <line number> (to list source code) x <variable name> (to examine a variable; only works if code is not compiled with optimization) x 0x4269978 (to examine a memory location) ? (help) q (quit) By hitting Enter, you repeat the last command. Written by &name-andreas-mohr; &email-andreas-mohr; Wine uses several different kinds of memory addresses. Win32/"normal" Wine addresses/Linux: linear addresses. 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). Win16 "enhanced mode": segmented addresses. 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 *always* 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. Example: 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. DOS/Win16 "standard mode" 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. 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 ;-) The Windows' debugging API uses a registry entry to know which debugger to invoke when an unhandled exception occurs (see for some details). Two values in key "MACHINE\\Software\\Microsoft\\Windows NT\\CurrentVersion\\AeDebug" Determine the behavior: Debugger: this is the command line used to launch the debugger (it uses two printf formats (%ld) to pass context dependent information to the debugger). You should put here a complete path to your debugger (WineDbg 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 ! You can also set a shell script to launch the debugger. In this case, you need to be sure that the invocation in this shell script is of the form: WINEPRELOAD=<path_to_winedbg.so> exec wine $* (Shell script must use exec, and the debugger .so file must be preloaded to override the shell script information). Auto: 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. A regular Wine registry looks like: [MACHINE\\Software\\Microsoft\\Windows NT\\CurrentVersion\\AeDebug] 957636538 "Auto"=dword:00000001 "Debugger"="/usr/local/bin/winedbg %ld %ld" creating this key is mandatory. Not doing so will not fire the debugger when an exception occurs. wineinstall 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 [MACHINE\\Software\\Microsoft\\Windows NT\\CurrentVersion\\AeDebug] key before running again wineinstall to regenerate this key. WineDbg can be configured thru a number of options. Those options are stored in the registry, on a per user basis. The key is (in my registry) [eric\\Software\\Wine\\WineDbg] Those options can be read/written while inside WineDbg, as part of the debugger expressions. To refer to one of these options, its name must be prefixed by a $ sign. For example, set $BreakAllThreadsStartup = 1 sets the option BreakAllThreadsStartup to TRUE. All the options are read from the registry when WineDbg starts (if no corresponding value is found, a default value is used), and are written back to the registry when WineDbg exits (hence, all modifications to those options are automatically saved when WineDbg terminates). Here's the list of all options: BreakAllThreadsStartup Set to TRUE if at all threads start-up the debugger stops set to FALSE if only at the first thread startup of a given process the debugger stops. FALSE by default. BreakOnCritSectTimeOut Set to TRUE if the debugger stops when a critical section times out (5 minutes); TRUE by default. BreakOnAttach Set to TRUE if when WineDbg attaches to an existing process after an unhandled exception, WineDbg 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 FALSE. BreakOnFirstChance 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 decides either to resume execution (see WineDbg's cont command) or pass the exception up to the exception handler chain in the program (if it exists) (WineDbg implements this thru the pass 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 BreakOnFirstChance exception is TRUE, then winedbg is entered for both first and last chance execptions (to FALSE, it's only entered for last chance exceptions). BreakOnDllLoad Set to TRUE if the debugger stops when a DLL is loaded into memory; when the debugger is invoked after a crash, the DLLs already mapped in memory will not trigger this break. FALSE by default. ConChannelMask Mask of active debugger output channels on console StdChannelMask Mask of active debugger output channels on stderr UseXTerm Set to TRUE if the debugger uses its own xterm window for console input/output. Set to FALSE if the debugger uses the current Unix console for input/output Those last 3 variables are jointly used in two generic ways: default ConChannelMask = DBG_CHN_MESG (1) StdChannelMask = 0 UseXTerm = 1 In this case, all input/output goes into a specific xterm window (but all debug messages TRACE, WARN... still goes to tty where wine is run from). to have all input/output go into the tty where Wine was started from (to be used in a X11-free environment) ConChannelMask = 0 StdChannelMask = DBG_CHN_MESG (1) UseXTerm = 1 Those variables also allow, for example for debugging purposes, to use: ConChannelMask = 0xfff StdChannelMask = 0xfff UseXTerm = 1 This allows to redirect all WineDbg output to both tty Wine was started from, and xterm debugging window. If Wine (or WineDbg) was started with a redirection of stdout and/or stderr to a file (with for example >& shell redirect command), you'll get in that file both outputs. It may be interesting to look in the relay trace for specific values which the process segv'ed on. ThreadId ID of the W-thread currently examined by the debugger ProcessId ID of the W-thread currently examined by the debugger <registers> All CPU registers are also available The ThreadId and ProcessId variables can be handy to set conditional breakpoints on a given thread or process. abort aborts the debugger quit exits the debugger attach N attach to a W-process (N is its ID). IDs can be obtained thru walk process command help prints some help on the commands help info prints some help on info commands mode 16 switch to 16 bit mode mode 32 switch to 32 bit mode cont continue execution until next breakpoint or exception. pass pass the exception event up to the filter chain. step continue execution until next C line of code (enters function call) next continue execution until next C line of code (doesn't enter function call) stepi execute next assembly instruction (enters function call) nexti execute next assembly instruction (doesn't enter function call) finish do nexti commands until current function is exited cont, step, next, stepi, nexti can be postfixed by a number (N), meaning that the command must be executed N times. enable N enables (break|watch)point #N disable N disables (break|watch)point #N delete N deletes (break|watch)point #N cond N removes any a existing condition to (break|watch)point N cond N <expr> adds condition <expr> to (break|watch)point N. <expr> will be evaluated each time the breakpoint is hit. If the result is a zero value, the breakpoint isn't triggered break * N adds a breakpoint at address N break <id> adds a breakpoint at the address of symbol <id> break <id> N adds a breakpoint at the address of symbol <id> (N ?) break N adds a breakpoint at line N of current source file break adds a breakpoint at current $pc address watch * N adds a watch command (on write) at address N (on 4 bytes) watch <id> adds a watch command (on write) at the address of symbol <id> info break lists all (break|watch)points (with state) When setting a breakpoint on an <id>, if several symbols with this <id> exist, the debugger will prompt for the symbol you want to use. Pick up the one you want from its number. bt print calling stack of current thread bt N print calling stack of thread of ID N (note: this doesn't change the position of the current frame as manipulated by the up & dn commands) up goes up one frame in current thread's stack up N goes up N frames in current thread's stack dn goes down one frame in current thread's stack dn N goes down N frames in current thread's stack frame N set N as the current frame for current thread's stack info local prints information on local variables for current function show dir dir <pathname> dir symbolfile <module> <pathname> list lists 10 source lines from current position list - lists 10 source lines before current position list N lists 10 source lines from line N in current file list <path>:N lists 10 source lines from line N in file <path> list <id> lists 10 source lines of function <id> list * N lists 10 source lines from address N You can specify the end target (to change the 10 lines value) using the ','. For example: list 123, 234 lists source lines from line 123 up to line 234 in current file list foo.c:1,56 lists source lines from line 1 up to 56 in file foo.c A display is an expression that's evaluated and printed after the execution of any WineDbg command. display lists the active displays info display (same as above command) display <expr> adds a display for expression <expr> display /fmt <expr> adds a display for expression <expr>. Printing evaluated <expr> is done using the given format (see print command for more on formats) del display N deletes display #N undisplay N (same as del display) disas disassemble from current position disas <expr> disassemble from address <expr> disas <expr>,<expr>disassembles code between addresses specified by the two <expr> info class <id> prints information on Windows's class <id> walk class lists all Windows' class registered in Wine info share lists all the dynamic libraries loaded the debugged program (including .so files, NE and PE DLLs) info module N prints information on module of handle N walk module lists all modules loaded by debugged program info queue N prints information on Wine's queue N walk queue lists all queues allocated in Wine info regs prints the value of CPU register info segment N prints information on segment N info segment lists all allocated segments info stack prints the values on top of the stack info map lists all virtual mappings used by the debugged program info wnd N prints information of Window of handle N walk wnd lists all the window hierarchy starting from the desktop window walk wnd N lists all the window hierarchy starting from the window of handle N walk process lists all w-processes in Wine session walk thread lists all w-threads in Wine session walk modref (no longer avail) x <expr> examines memory at <expr> address x /fmt <expr> examines memory at <expr> address using format /fmt print <expr> prints the value of <expr> (possibly using its type) print /fmt <expr> prints the value of <expr> (possibly using its type) set <lval>=<expr> writes the value of <expr> in <lval> whatis <expr> prints the C type of expression <expr> /fmt is either /<letter> or /<count><letter> letter can be s => an ASCII string u => an Unicode UTF16 string i => instructions (disassemble) x => 32 bit unsigned hexadecimal integer d => 32 bit signed decimal integer w => 16 bit unsigned hexadecimal integer c => character (only printable 0x20-0x7f are actually printed) b => 8 bit unsigned hexadecimal integer Expressions in Wine Debugger are mostly written in a C form. However, there are a few discrepancies: Identifiers can take a '.' in their names. This allow mainly to access symbols from different DLLs like USER32.DLL.CreateWindowA Because of previous rule, fields access from a struct must be written as: my_struct . my_field (note the spaces after and before the dot). You can also use other debuggers (like gdb), but you must be aware of a few items: You need to attach the unix debugger to the correct unix process (representing the correct windows thread) (you can "guess" it from a ps fax for example: When running the emulator, usually the first two upids are for the Windows' application running the desktop, the first thread of the application is generally the third upid; when running a Winelib program, the first thread of the application is generally the first upid) Even if latest gdb implements the notion of threads, it won't work with Wine because the thread abstraction used for implementing Windows' thread is not 100% mapped onto the linux posix threads implementation. It means that you'll have to spawn a different gdb session for each Windows' thread you wish to debug. Following text written by &name-andreas-mohr; &email-andreas-mohr; Here's how to get info about the current execution status of a certain Wine process: Change into your Wine source dir and enter: $ gdb wine Switch to another console and enter ps ax | grep wine to find all wine processes. Inside gdb, repeat for all Wine processes: (gdb) attach PID with PID being the process ID of one of the Wine processes. Use (gdb) bt 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: (gdb) n or maybe even (gdb) b SomeFunction and (gdb) c to set a breakpoint at a certain function and continue up to that function. Finally you can enter (gdb) detach to detach from the Wine process. 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. +----------------------------------+---------------------------------+ | WineDbg | gdb | +----------------------------------+---------------------------------+ |WineDbg debugs a Windows' process:|gdb debugs a Windows' thread: | |+ the various threads will be |+ a separate gdb session is | | handled by the same WineDbg | needed for each thread of | | session | Windows' process | |+ a breakpoint will be triggered |+ a breakpoint will be triggered | | for any thread of the w-process | only for the w-thread debugged | +----------------------------------+---------------------------------+ |WineDbg supports debug information|gdb supports debug information | |from: |from: | |+ stabs (standard Unix format) |+ stabs (standard Unix format) | |+ Microsoft's C, CodeView, .DBG | | +----------------------------------+---------------------------------+ 16 bit processes are not supported (but calls to 16 bit code in 32 bit applications are).