On Sun, Jul 18, 2010 at 10:47 PM, TP <wing...@gmail.com> wrote: > On Sun, Jul 18, 2010 at 2:38 PM, Dino Viehland <di...@microsoft.com> wrote: >> TP wrote: >>> I'm using IronPython 2.6.1 for Net 2.0 and VS2008 on Windows XP SP3. >>> >>> I have a python script that lets me access the Leptonica Image >>> Processing C library (http://leptonica.com/) using the ctypes module. >>> >>> Everything seems to work fine with cpython 2.6. I can correctly load >>> leptonlib.dll, create leptonica PIX images, manipulate them, and even >>> display them using PyQT. I can use VS2008 to put breakpoints on >>> leptonica C functions and step through the C code in the VS2008 >>> debugger. >>> >>> I thought I'd give IronPython a try since it also has ctypes, but I >>> ran into a number of problems. >>> >>> The leptonlib.dll must be loading since I am able to correctly get >>> back the library's version string. That is the following works: >>> >>> _getLeptonlibVersion = _leptonlib.getLeptonlibVersion >>> _getLeptonlibVersion.restype = ctypes.c_void_p >>> addr = _getLeptonlibVersion() >>> version = ctypes.string_at(addr) >>> >>> However the following code doesn't seem to work under IronPython 2.6.1: >>> >>> pix = Pix(dimensions=(10,20,1)) >>> >>> where essentially the following is called: >>> >>> _pix = ctypes.c_void_p() >>> _pix.value = _leptonlib.pixCreate(width, height, depth) >>> self._pix = _pix >>> >>> and I want to treat _pix as an opaque ptr I just hand back to >>> leptonica whenever it needs it. For example: >>> >>> def height(self): >>> """Get height of pix in pixels.""" >>> return _leptonlib.pixGetHeight(self._pix) >>> >>> Which works with cpython but returns something other than 20 with >>> IronPython. >>> >>> By specifying "-X:Debug -X:FullFrames -X:Tracing leptonica.py" as the >>> arguments to C:\Program Files\IronPython 2.6\ipy.exe I can get >>> IronPython to correctly stop at places in my script where I put: >>> >>> import pdb >>> pdb.set_trace() >>> >>> when I debug leptonlibd.dll with VS2008. However, my breakpoints on >>> leptonica's C functions never seem to get hit. This works fine if I >>> instead use python26.exe as command to launch when debugging. >> >> You should only need -X:Debug to get debugging under VS. pdb uses a >> more Pythonic form of debugging but there's no support for it in VS. > > Let me be clear here. I am using the VS2008 Solution that I use to > create leptonlib.dll. I am debugging that dll by right-clicking its > project and setting its Configuration Properties | Debugging tab to: > > Command: C:\Program Files\IronPython 2.6\ipy.exe > Arguments: -X:Debug -X:FullFrames -X:Tracing -i leptonica.py > Working Directory: C:\leptonica\ > > If I only use -X:Debug as you suggest I get the following error: > > Traceback (most recent call last): > File "leptonica.py", line 458, in <module> > File "leptonica.py", line 176, in __init__ > File "C:\Program Files\IronPython 2.6\Lib\pdb.py", line 1220, in set_trace > AttributeError: 'module' object has no attribute '_getframe'>>> > > Googling, I determined that I needed to add at least -X:FullFrames, > and by trial and error I found I also needed -X:Tracing. (I wasn't > able to find any documentation on ipy.exe's command line switches? I > just ran "ipy.exe -h" to dump out the short help description and took > a wild guess at which might be useful) > >>> >>> Ideally I like to have the VS Debugger stop in leptonlibd.dll's >>> pixCreate() C function just before it returns its value so I can >>> compare that to what I get back on the IronPython side. >>> >>> So how's does one use VS2008 to step through C functions in DLLs that >>> are loaded by IronPython and the ctypes module? >> >> Do you have symbols (.PDB files) for leptonlibd.dll? You'll need symbols >> to be able to step through the C code. You can still probably set a >> breakpoint >> in the function because it's DLL exported - I think you can debug->new >> breakpoint and enter leptonlibd!pixCreate. Even w/o symbols you could >> step through the assembly. > > leptonlibd.dll is created with the C7 Compatible (/Z7) compiler > switch. This embeds the debugging info directly in the DLL so no .pdb > file is produced. It also does NOT use pre-compiled headers. > > I might also point out that the same exact .dll will hit breakpoints > if debugged with python26.exe rather than ipy.exe. Perhaps since > ipy.exe is built on top of .NET the VS2008 debugger handles any .dll's > loaded by it differently? I know for example that the VS2008 debugger > didn't like trying to run the IronPython for NET 4.0 version of > ipy.exe (I gather you have to use VS2010 if you want to do that). > > Trying to set a breaking at leptonlibd!pixCreate didn't work. > >>> >>> Secondly, am I using ctypes wrong, and does my code only work by >>> happenstance for cpython. >> >> I don't see anything particularly wrong on your side and this looks like >> a pretty simple call. I would assume the C functions are defined as: >> >> void* pixCreate(int width, int height, int depth); >> int pixGetHeight(void* pixel); > > That's correct. > >> >> I would hope we're getting all of this right as it seems like simple stuff >> that should be tested somewhere. My first guess would be maybe we're >> getting the calling convention wrong. Maybe it needs to be a WinDLL instead >> of a CDLL? Maybe there's a check in the Python code for sys.platform which >> is looking for win32 and uses WinDLL to open the DLL instead of CDLL on >> Windows? > > More information on the problem: > > I decided to explicitly set the restype even though it's the default > return type. I get the same exact behavior as my original code. Works > with cpython, doesn't work with IronPython 2.6.1. > > If I have with the following python code: > > _pix = ctypes.c_void_p() > _pixCreate = _leptonlib.pixCreate > _pixCreate.restype = ctypes.c_int > import pdb > pdb.set_trace() > > _pix.value = _pixCreate(width, height, depth) > > I can do the following in the Command Window after pdb breaks into the script: > > > leptonica.py(180)__init__() > -> _pix.value = _pixCreate(width, height, depth) > (Pdb) n > > leptonica.py(181)__init__() > -> self._pix = _pix > (Pdb) _pix.value > *** AttributeError: 'cell' object has no attribute 'value' > > This is a bit strange since I just assigned to _pix.value. > Investigating further: > > (Pdb) _pix > <cell at 43: c_void_p object at 44> > > So instead of assigning to _pix.value (that is changing an attribute > of _pix), IronPython is clobbering _pix? > > If I instead separately assign the result of pixCreate() to a > temporary variable: > > width, height, depth = dimensions > _pix = ctypes.c_void_p() > _pixCreate = _leptonlib.pixCreate > _pixCreate.restype = ctypes.c_int > import pdb > pdb.set_trace() > > addr = _pixCreate(width, height, depth) > _pix.value = addr > > Once pdb stops the script: > > > leptonica.py(178)__init__() > -> addr = _pixCreate(width, height, depth) > (Pdb) n > > leptonica.py(179)__init__() > -> _pix.value = addr > (Pdb) addr > <cell at 43: int object at 44> > (Pdb) type(addr) > <type 'cell'> > (Pdb) dir(addr) > ['__class__', '__cmp__', '__delattr__', '__doc__', '__eq__', '__format__', > '__getattribute__', '__hash__', '__init__', '__ne__', '__new__', > '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', > '__sizeof__', '__str__', '__subclasshook__', 'cell_contents'] > (Pdb) type(addr.cell_contents) > <type 'int'> > (Pdb) addr.cell_contents > 77491296 > > So instead of returning an int, ctypes under IronPython is returning a > "cell" in this case for some reason? > > Compare this to what I get with cpython. If I change the leptonlib.dll > project Configuration Properties | Debugging tab to: > > Command: c:\Python26\python26.exe > Arguments: -i leptonica.py > Working Directory: C:\leptonica\ > > Debugging by typing F5 (or choosing Debug > Start Debugging) without > changing leptonica.py or leptonlibd.dll in any way, I then hit all my > breakpoints set in leptonlibd.dll. I get warning messages about > python.exe having stopped for each breakpoint and I just click the > Continue button to close them. After I type F5 to get past all my C > function breakpoints, pdb stops my script with: > > > leptonica.py(178)__init__() > -> addr = _pixCreate(width, height, depth) > (Pdb) n > > leptonica.py(179)__init__() > -> _pix.value = addr > (Pdb) addr > 19492760 > (Pdb) hex(addr) > '0x1296f98' > > and 0x1296f98 matches what I see for the return value of pixCreate() > from the VS2008 debugger. > > I also tried debugging my leptonica.py script by following the > directions in the IronPython tutorial. I made a new Solution with the > following Debugging properties: > > Command: C:\Program Files\IronPython 2.6\ipy.exe > Arguments: -X:Debug -i leptonica.py > Working Directory: C:\leptonica\ > > I added my leptonlib.vcprog file to this solution by right-clicking it > and choosing Add > Existing Project. I again set a breakpoint at the C > function pixCreate(). > > I also set various breakpoints in my leptonica.py script. > > Pressing F5 to Start Debugging, I now hit my leptonica.py breakpoints > but still don't hit any C function breakpoints. > > From the locals window I can see that addr is: > > addr 0x00bf6ea0 object {int} > > Looking in a Memory window at "addr" I see: > > 0x06AAB590 79332d70 00bf6ea0 00000000 793042f4 00000001 33b4c9bc > p-3y n¿.....ôB0y.....É´3 > > So there's something else at "addr", but the next int is 0x00bf6ea0 again. > > The memory at 0x00bf6ea0 looks correct: > > 0x00BF6EA0 0a 00 00 00 14 00 00 00 01 00 00 00 01 00 00 00 01 00 > 00 00 00 00 ...................... > 0x00BF6EB6 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > f8 6e bf 00 ..................øn¿. > 0x00BF6ECC fd fd fd fd 10 00 0b 00 f2 01 0c 00 80 6e bf 00 00 00 > 00 00 00 00 ýýýý....ò...€n¿....... > 0x00BF6EE2 00 00 00 00 00 00 50 00 00 00 01 00 00 00 4d 00 00 00 > fd fd fd fd ......P.......M...ýýýý > > At least it looks to me like those are indeed ints for width, height & > depth which is what a PIX starts out with. > > After: > > _pix.value = addr > > I see this in the locals window: > > _pix "ctypes.c_void_p instance" object > {IronPython.NewTypes.IronPython.Modules.SimpleCData_4$4} > > In the Immediate window I get: > > _pix > "ctypes.c_void_p instance" > base {IronPython.Modules.CTypes.SimpleCData}: "ctypes.c_void_p instance" > .class: PythonType: "c_void_p" > .dict: null > .slots_and_weakref: null > > But I am unable to figure out how to tell what the "value" of _pix is? >
Since there seems to be something strange going on with using IronPython, pdb & VS2008, I decided to just put in some printf's in leptonlib, rebuild it, and forget about using debuggers. Here's the results: [C:\leptonica]python26 leptonica.py pixCreate() returns 01293340 addr=01293340 _pix.value = 01293340 ctypes.addressof(_pix) = 00c78878 pixGetWidth() addr=01293340 width = 10 height = 20 depth = 1 [C:\leptonica]ipy leptonica.py pixCreate() returns 046d4f60 addr=046d4f60 _pix.value = 046d4f60 ctypes.addressof(_pix) = 0353c698 pixGetWidth() addr=0353c698 width = 74272608 height = 1442168 depth = 131074 So despite what it looks like from pdb, IronPython is correctly setting the ctypes.c_void_p. The problem is that when it passes the ctypes.c_void_p back to a C function it gives the address of the ctypes.c_void_p, instead of the ptr that it contains. I'd still like to know: Why can't I use VS2008 to set breakpoints on C functions in DLLs that are loaded by IronPython and the ctypes module? How to see the value of ctypes.c_void_p instances in the VS2008 debugger. _______________________________________________ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
