Question

每当我使用ctypes将共享库（.so）加载到Python中并调用其中一个使用OpenCV过滤器引擎（如cvErode或cvDilate）的过程时，解释器就会深入到OpenCV代码中。如果我在C程序中使用dlopen加载相同的库并调用相同的过程，一切正常。

我在另一篇文章中读过它可能与gcc使用的ABI有关，并且python必须使用与python解释器编译的相同版本的gcc进行编译才能使用。但是在我的情况下它是4.4.5，所以这不应该是一个问题。 OpenCV库也使用相同版本的gcc进行编译。

如何构建共享库：

g++ -g -shared -lopencv_core -lopencv_imgproc -lopencv_calib3d -lopencv_video -lopencv_features2d -lopencv_ml -lopencv_highgui -lopencv_objdetect -lopencv_contrib -lopencv_legacy -o thumbsplit.so thumbsplit.cpp

如何包装共享库：

extern "C" {

int is_thumbsheet(char * image_path){
    Image image;
    image.read(image_path);
    int width = image.columns();
    int height = image.rows();
    int BOUND_CHANGE = 7000;
    int test_height = 0;

    if( width > height ){
        return 0;
    }else{
        test_height = width;
    }
    vector<int> test_rows = getRows(image, width, test_height, BOUND_CHANGE);
    vector<int> test_cols = getCols(image, width, test_height, BOUND_CHANGE);

    vector<Box> test_boxes = createBoxes(test_rows,test_cols,width,height);
    if( test_boxes.size() > 6 ){
        return 1;
    }else{
        return 0;
    }
}

int cut_thumbs(char * image_path, char * thumb_path){
    Image image;
    image.read(image_path);
    int width = image.columns();
    int height = image.rows();
    int BOUND_CHANGE = 7000;
    vector<int> rows = getRows(image, width, height, BOUND_CHANGE);
    vector<int> cols = getCols(image, width, height, BOUND_CHANGE);

    //drawDebugLines(rows, cols, width, height);

    vector<Box> boxes = createBoxes(rows,cols,width,height);
    //printBoxes(boxes);
    char path[0x100];
    for( int i=0 ; i < boxes.size() ; i++ ){
        sprintf(path, "%s%d.jpg", thumb_path, i);
        boxes[i].saveBox(image, path);
    }


    return 0;
}

} // C

如何在python中加载共享库过程：

import ctypes, os

def load_lib():
lib_path = "%s/%s"%(os.path.realpath(os.path.dirname(__file__)), "thumbsplit.so")
lib = ctypes.CDLL(lib_path)
return lib

def is_thumbsheet(image_path):

lib = load_lib()
if lib.is_thumbsheet(image_path):
    return True
else:
    return False

def cut_thumbs(image_path, thumbs_path):

lib = load_lib()
lib.cut_thumbs(image_path, thumbs_path)

is_thumbsheet("/home/rolf/test/imageproc/full9.jpg") # this segfaults

GDB输出：

$ gdb python
GNU gdb (GDB) 7.0.1-debian
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i486-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /usr/bin/python...(no debugging symbols found)...done.
(gdb) run thumbsheet.py
Starting program: /usr/bin/python thumbsheet.py
[Thread debugging using libthread_db enabled]
0xb6330a12

Program received signal SIGSEGV, Segmentation fault.
0xb76fe2dc in cv::FilterEngine::start(cv::Size_<int>, cv::Rect_<int>, int) () from /usr/local/lib/libopencv_imgproc.so.2.3
(gdb) info stack
#0  0xb76fe2dc in cv::FilterEngine::start(cv::Size_<int>, cv::Rect_<int>, int) () from /usr/local/lib/libopencv_imgproc.so.2.3
#1  0xb76feb41 in cv::FilterEngine::start(cv::Mat const&, cv::Rect_<int> const&, bool, int) ()
   from /usr/local/lib/libopencv_imgproc.so.2.3
#2  0xb770a52b in cv::FilterEngine::apply(cv::Mat const&, cv::Mat&, cv::Rect_<int> const&, cv::Point_<int>, bool) ()
   from /usr/local/lib/libopencv_imgproc.so.2.3
#3  0xb764bf8a in cv::morphOp(int, cv::_InputArray const&, cv::_OutputArray const&, cv::_InputArray const&, cv::Point_<int>, int, int, cv::Scalar_<double> const&) () from /usr/local/lib/libopencv_imgproc.so.2.3
#4  0xb764d2ce in cv::erode(cv::_InputArray const&, cv::_OutputArray const&, cv::_InputArray const&, cv::Point_<int>, int, int, cv::Scalar_<double> const&) () from /usr/local/lib/libopencv_imgproc.so.2.3
#5  0xb764d62e in cvErode () from /usr/local/lib/libopencv_imgproc.so.2.3
#6  0xb7fd7adb in seperate::findSeperatedBoxes (img=0x8351d70) at seperate.cpp:189
#7  0xb7fd7fcf in seperate::trySeperatedBoxes (img=0x8351d70, percentage_boxed=0xbfffefec) at seperate.cpp:202
#8  0xb7fda00c in is_thumbsheet (image_path=0xb7c1bf74 "/home/rolf/test/imageproc/full9.jpg") at thumbsplit.cpp:39
#9  0xb7a047df in ffi_call_SYSV () from /usr/lib/python2.6/lib-dynload/_ctypes.so
#10 0xb7a0461e in ffi_call () from /usr/lib/python2.6/lib-dynload/_ctypes.so
#11 0xb79ff27d in _CallProc () from /usr/lib/python2.6/lib-dynload/_ctypes.so
#12 0xb79f6d7e in ?? () from /usr/lib/python2.6/lib-dynload/_ctypes.so
#13 0x0806232a in PyObject_Call ()
#14 0x080e016b in PyEval_EvalFrameEx ()
#15 0x080e18b0 in PyEval_EvalFrameEx ()
#16 0x080e2507 in PyEval_EvalCodeEx ()
#17 0x080e2607 in PyEval_EvalCode ()
#18 0x080ffcbd in PyRun_FileExFlags ()
#19 0x080fff22 in PyRun_SimpleFileExFlags ()
#20 0x0805dd81 in Py_Main ()
#21 0x0805cf6b in main ()
(gdb) x/i 0xb76fe2dc
0xb76fe2dc <_ZN2cv12FilterEngine5startENS_5Size_IiEENS_5Rect_IiEEi+1212>:   movdqa %xmm3,0x30(%esp)
(gdb)

GCC / G ++版本：

$ python
Python 2.6.6 (r266:84292, Dec 27 2010, 00:02:40) 
[GCC 4.4.5] on linux2

$ gcc --version
gcc (Debian 4.4.5-8) 4.4.5

$ g++ --version
g++ (Debian 4.4.5-8) 4.4.5

OpenCV是版本2.3.1，使用此版本的gcc（4.4.5-8）从源代码构建

Answer 1

我找到了解决方案。对于SSE指令，堆栈需要重新调整为16个字节。如果我使用-mstackrealign构建共享库，它可以完美地加载并从python调用。

Qt, GCC, SSE and stack alignment

当通过python ctypes使用时，opencv调用共享库段错误

1 个答案: