Ctypes“符号未找到”用于OSX中的动态库 [英] Ctypes "symbol not found" for dynamic library in OSX

问题描述

我制作了一个C ++库，并从它建立了一个.dylib动态库。但是，当我用ctypes加载它时，它会失败。有些东西似乎没有正确链接。我不知道为什么。错误（相关部分）：

pre code $ cscalelib.setup_framebuffer（flip，surface.frame_buffer，surface.texture，surface._scale [ 0]，surface._scale [1]）$ ​​b $ b文件/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/ctypes/__init__.py，第325行，位于__getattr__
func = self .__ getitem __（name）
文件/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/ctypes/__init__.py，第330行，位于__getitem__
func = self._FuncPtr（（name_or_ordinal，self））
AttributeError：dlsym（0x56ecd0，setup_framebuffer）：找不到符号

以下是仍在进行中的C ++代码，但应该与我目前使用的代码一致。

  #include< OpenGL / gl.h> 
 #include< OpenGL / glu.h> 
 #include< vector.h> 
 
 void setup_framebuffer（bool flip，GLuint frame_buffer_id，gluint texture_id，int width，int height）{
 glBindFramebufferEXT（GL_FRAMEBUFFER_EXT，frame_buffer_id）; 
 glFramebufferTexture2DEXT（GL_FRAMEBUFFER_EXT，GL_COLOR_ATTACHMENT0_EXT，GL_TEXTURE_2D，texture_id，0）; 
 glPushAttrib（GL_VIEWPORT_BIT）; 
 glViewport（0,0，width，height）; 
 glMatrixMode（GL_PROJECTION）; 
 glLoadIdentity（）; //加载投影矩阵
 if（flip）{
 gluOrtho2D（0，width，height，0）; 
} else {
 gluOrtho2D（0，width，0，height）; 
} 
} 
 void end_framebuffer（）{
 glPopAttrib（）; 
 glBindFramebufferEXT（GL_FRAMEBUFFER_EXT，0）; 
 glMatrixMode（GL_PROJECTION）; 
 glLoadIdentity（）; //加载投影矩阵
 gluOrtho2D（0,1280,720,0）; //设置一个正交视图
} 
 void add_lines（bool antialias，vector< vector< double>> coordinate，double w，double r，double g，double b，double a）{
 glDisable（GL_TEXTURE_2D）; 
 if（antialias）{
 glEnable（GL_LINE_SMOOTH）; //启用线条平滑。 
} 
 glColor4d（r，g，b，a）; 
 glLineWidth（w）; 
 glBegin（GL_LINE_STRIP）; 
 for（int x = 0; x< coordinates.size（）; x ++）{
 glVertex2d（coordinates [x] [0]，coordinates [x] [1]）; 
} 
 glEnd（）; 
 if（antialias）{
 glDisable（GL_LINE_SMOOTH）; //禁用线条平滑。 
} 
 glEnable（GL_TEXTURE_2D）; 
} 
  

我将它编译为：

g ++ -dynamiclib CPPEXTSCALELIB.cp -framework opengl -arch i386 -o CPPEXTSCALELIB.dylib

以下是用...表示不相关部分的Python代码。

  ... 
 from ctypes import * 
 ... 
 cscalelib = CDLL （os.path.dirname（sys.argv [0]）+/CPPEXTSCALELIB.dylib）
 ... 
 def setup_framebuffer（surface，flip = False）：
 #Create texture如果尚未完成，
如果surface.texture为None：
 create_texture（surface）
 #Render子级父级
如果surface.frame_buffer为None：
 surface.frame_buffer = glGenFramebuffersEXT（1）
 cscalelib.setup_framebuffer（flip，surface.frame_buffer，surface.texture，surface._scale [0]，surface._scale [1]）$ ​​b $ b ... 
 < 
 
解决方案
 >这个问题很可能是因为你正在使用C ++，因此也是e函数名称将被改变并使用C ++调用约定。如果使用 externC声明函数，那么它应该以可从C代码（以及来自Python的CTypes模块）调用的方式导出。
 
I have made a C++ library and have built a .dylib dynamic library from it. However when I load it with ctypes, it fails. Something doesn't seem to have linked properly. I have no idea why. The error (The relevant part):
    cscalelib.setup_framebuffer(flip,surface.frame_buffer,surface.texture,surface._scale[0],surface._scale[1])
  File "/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/ctypes/__init__.py", line 325, in __getattr__
    func = self.__getitem__(name)
  File "/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/ctypes/__init__.py", line 330, in __getitem__
    func = self._FuncPtr((name_or_ordinal, self))
AttributeError: dlsym(0x56ecd0, setup_framebuffer): symbol not found
Here's the C++ code which is still in progress but should work with what I have so far.
#include <OpenGL/gl.h>
#include <OpenGL/glu.h>
#include <vector.h>

void setup_framebuffer(bool flip,GLuint frame_buffer_id,GLuint texture_id,int width,int height){
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, frame_buffer_id);
    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, texture_id, 0);
    glPushAttrib(GL_VIEWPORT_BIT);
    glViewport(0,0,width,height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity(); //Load the projection matrix
    if (flip){
        gluOrtho2D(0,width,height,0);
    }else{
        gluOrtho2D(0,width,0,height);
    }
}
void end_framebuffer(){
    glPopAttrib();
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity(); //Load the projection matrix
    gluOrtho2D(0,1280,720,0); //Set an orthorgraphic view
}
void add_lines(bool antialias,vector< vector<double> > coordinates,double w,double r,double g, double b,double a){
    glDisable(GL_TEXTURE_2D);
    if (antialias){
        glEnable(GL_LINE_SMOOTH); //Enable line smoothing.
    }
    glColor4d(r,g,b,a);
    glLineWidth(w);
    glBegin(GL_LINE_STRIP);
    for (int x = 0; x < coordinates.size(); x++) {
        glVertex2d(coordinates[x][0],coordinates[x][1]);
    }
    glEnd();
    if (antialias){
        glDisable(GL_LINE_SMOOTH); //Disable line smoothing.
    }
    glEnable(GL_TEXTURE_2D);
}
I compiled it with:

g++ -dynamiclib CPPEXTSCALELIB.cp -framework opengl -arch i386 -o CPPEXTSCALELIB.dylib

Here's the Python code with "..." to represent irrelevant parts.
...
from ctypes import *
...
cscalelib = CDLL(os.path.dirname(sys.argv[0]) + "/CPPEXTSCALELIB.dylib")
...
def setup_framebuffer(surface,flip=False):
    #Create texture if not done already
    if surface.texture is None:
        create_texture(surface)
    #Render child to parent
    if surface.frame_buffer is None:
        surface.frame_buffer = glGenFramebuffersEXT(1)
    cscalelib.setup_framebuffer(flip,surface.frame_buffer,surface.texture,surface._scale[0],surface._scale[1])
...
Thank you.
解决方案
The problem is most likely the fact that you are using C++, and hence the function name will be mangled and use C++ calling conventions. If you declare the function with extern "C" then it should be exported in such a way as to callable from C code (and from Python's CTypes module).

                        
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