为什么我会得到"ImportError: dlopen(.)：符号未找到“这个错误？当我在python上导入库时

Question

我一直在用CFFI在我的python项目中使用一些C代码，但是当我试图构建并导入我构建的import _chebyshev_cffi库时，我会得到以下错误：

ImportError: dlopen(/Users/Username/Documents/code project/_chebyshev_cffi.cpython-35m-darwin.so, 2): Symbol not found: _elementary_clenshaw_step_real
Referenced from: /Users/Username/Documents/code project/_chebyshev_cffi.cpython-35m-darwin.so
Expected in: flat namespace

我不知道这里出了什么问题，我一直找不到关于这个错误的信息，我希望能提供任何帮助。我正在使用MacOS和anaconda发行版用于python，cffi似乎安装正确。

编辑:我可能应该补充一下，我实际上期望的函数在它之前不应该有下划线。应该是“elementary_clenshaw_step_real而不是_elementary_clenshaw_step_real”。下面是源代码：

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Created on Tue Sep  3 17:00:38 2019

@author: anonymous
"""

from cffi import FFI
ffibuilder = FFI()

ffibuilder.cdef("void elementary_clenshaw_step_real(const int dim_x, const char * restrict boundary_condition, const double * restrict wfc, const double * restrict psi, double * restrict psi_old, const double c_coef, const double one_or_two, const int add_real, const double tunneling, const double * restrict disorder);")
ffibuilder.cdef("void chebyshev_clenshaw_real(const int dim_x, const int max_order, const char * restrict boundary_condition, double * wfc, double * psi, double * psi_old, const double tunneling, const double * disorder, const double *tab_coef, const double g_times_delta_t, const double e0_times_delta_t);")

ffibuilder.set_source("_chebyshev_cffi",
r"""
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#ifdef __ICC
#include <mathimf.h>
#else
#include <math.h>
#endif
#include <complex.h>

void __inline elementary_clenshaw_step_real(const int dim_x, const char * restrict boundary_condition, const double * restrict wfc, const double * restrict psi, double * restrict psi_old, const double c_coef, const double one_or_two, const int add_real, const double tunneling, const double * restrict disorder)
{
  int i; 
  if (add_real) {
    if (strcmp(boundary_condition,"periodic") == 0) {
      psi_old[0]=one_or_two*(disorder[0]*psi[0]-tunneling*(psi[1]+psi[dim_x-1]))+c_coef*wfc[0]-psi_old[0];
      psi_old[dim_x]=one_or_two*(disorder[0]*psi[dim_x]-tunneling*(psi[dim_x+1]+psi[2*dim_x-1]))+c_coef*wfc[dim_x]-psi_old[dim_x];
      psi_old[dim_x-1]=one_or_two*(disorder[dim_x-1]*psi[dim_x-1]-tunneling*(psi[0]+psi[dim_x-2]))+c_coef*wfc[dim_x-1]-psi_old[dim_x-1] ;
      psi_old[2*dim_x-1]=one_or_two*(disorder[dim_x-1]*psi[2*dim_x-1]-tunneling*(psi[dim_x]+psi[2*dim_x-2]))+c_coef*wfc[2*dim_x-1]-psi_old[2*dim_x-1];
    } else {
      psi_old[0]=one_or_two*(disorder[0]*psi[0]-tunneling*psi[1])+c_coef*wfc[0]-psi_old[0];
      psi_old[dim_x]=one_or_two*(disorder[0]*psi[dim_x]-tunneling*psi[dim_x+1])+c_coef*wfc[dim_x]-psi_old[dim_x];
      psi_old[dim_x-1]=one_or_two*(disorder[dim_x-1]*psi[dim_x-1]-tunneling*psi[dim_x-2])+c_coef*wfc[dim_x-1]-psi_old[dim_x-1] ;
      psi_old[2*dim_x-1]=one_or_two*(disorder[dim_x-1]*psi[2*dim_x-1]-tunneling*psi[2*dim_x-2])+c_coef*wfc[2*dim_x-1]-psi_old[2*dim_x-1];
    }  
#ifdef __clang__
#else
#pragma GCC ivdep
#ifdef __ICC
#pragma distribute_point
#endif
#endif
    for (i=1;i<dim_x-1;i++) {   
      psi_old[i]=one_or_two*(disorder[i]*psi[i]-tunneling*(psi[i+1]+psi[i-1]))+c_coef*wfc[i]-psi_old[i];
    }
#ifdef __clang__    
#else
#pragma GCC ivdep
#ifdef __ICC
#pragma distribute_point
#endif
#endif
    for (i=dim_x+1;i<2*dim_x-1;i++) {         
      psi_old[i]=one_or_two*(disorder[i-dim_x]*psi[i]-tunneling*(psi[i+1]+psi[i-1]))+c_coef*wfc[i]-psi_old[i];
    }    
  } else { 
    if (strcmp(boundary_condition,"periodic") == 0) {
      psi_old[0]=one_or_two*(disorder[0]*psi[0]-tunneling*(psi[1]+psi[dim_x-1]))-c_coef*wfc[dim_x]-psi_old[0];
      psi_old[dim_x]=one_or_two*(disorder[0]*psi[dim_x]-tunneling*(psi[dim_x+1]+psi[2*dim_x-1]))+c_coef*wfc[0]-psi_old[dim_x];
      psi_old[dim_x-1]=one_or_two*(disorder[dim_x-1]*psi[dim_x-1]-tunneling*(psi[0]+psi[dim_x-2]))-c_coef*wfc[2*dim_x-1]-psi_old[dim_x-1] ;
      psi_old[2*dim_x-1]=one_or_two*(disorder[dim_x-1]*psi[2*dim_x-1]-tunneling*(psi[dim_x]+psi[2*dim_x-2]))+c_coef*wfc[dim_x-1]-psi_old[2*dim_x-1];
    } else {
      psi_old[0]=one_or_two*(disorder[0]*psi[0]-tunneling*psi[1])-c_coef*wfc[dim_x]-psi_old[0];
      psi_old[dim_x]=one_or_two*(disorder[0]*psi[dim_x]-tunneling*psi[dim_x+1])+c_coef*wfc[0]-psi_old[dim_x];
      psi_old[dim_x-1]=one_or_two*(disorder[dim_x-1]*psi[dim_x-1]-tunneling*psi[dim_x-2])-c_coef*wfc[2*dim_x-1]-psi_old[dim_x-1] ;
      psi_old[2*dim_x-1]=one_or_two*(disorder[dim_x-1]*psi[2*dim_x-1]-tunneling*psi[2*dim_x-2])+c_coef*wfc[dim_x-1]-psi_old[2*dim_x-1];      
    }  
#ifdef __clang__
#else
#pragma GCC ivdep
#ifdef __ICC
#pragma distribute_point
#endif
#endif    
    for (i=1;i<dim_x-1;i++) {   
      psi_old[i]=one_or_two*(disorder[i]*psi[i]-tunneling*(psi[i+1]+psi[i-1]))-c_coef*wfc[i+dim_x]-psi_old[i];
    }
#ifdef __clang__
#else    
#pragma GCC ivdep
#ifdef __ICC
#pragma distribute_point
#endif
#endif
    for (i=dim_x+1;i<2*dim_x-1;i++) {         
      psi_old[i]=one_or_two*(disorder[i-dim_x]*psi[i]-tunneling*(psi[i+1]+psi[i-1]))+c_coef*wfc[i-dim_x]-psi_old[i];
    }        
  }    
  return;
}  

void chebyshev_clenshaw_real(const int dim_x, const int max_order,  const char * restrict boundary_condition, double * restrict wfc, double * restrict psi, double * restrict psi_old, const double tunneling, const double * restrict disorder, const double * restrict tab_coef, const double g_times_delta_t, const double e0_times_delta_t)
{
  int i, order;
  double argument;
  double cos_phase;
  double sin_phase;
  for (i=0;i<2*dim_x;i++) {
    psi[i] = tab_coef[max_order] * wfc[i];
  }
  elementary_clenshaw_step_real(dim_x, boundary_condition, wfc, psi, psi_old, tab_coef[max_order-1], 2.0, 0, tunneling, disorder);
// WARNING: max_order MUST be an even number, otherwise disaster guaranteed  
  for (order=max_order-2;order>1;order-=2) {  
//    printf("order = %d %d %lf %lf\n",order,(order+1)%2,tab_coef[order],tunneling); 
    elementary_clenshaw_step_real(dim_x, boundary_condition, wfc, psi_old, psi, tab_coef[order], 2.0, 1, tunneling, disorder);
    elementary_clenshaw_step_real(dim_x, boundary_condition, wfc, psi, psi_old, tab_coef[order-1], 2.0, 0, tunneling, disorder);
  }
  elementary_clenshaw_step_real(dim_x, boundary_condition, wfc, psi_old, psi, tab_coef[0], 1.0, 1, tunneling, disorder);
// apply nonlinear shift
  if (g_times_delta_t==0.0) {
    cos_phase=cos(e0_times_delta_t);    
    sin_phase=sin(e0_times_delta_t);
#ifdef __clang__
#else
#pragma GCC ivdep
#endif
    for (i=0;i<dim_x;i++) {
      wfc[i] = psi[i]*cos_phase+psi[i+dim_x]*sin_phase;
      wfc[i+dim_x] = psi[i+dim_x]*cos_phase-psi[i]*sin_phase;
   }  
  } else {
#ifdef __clang__
#else
#pragma GCC ivdep
#endif
    for (i=0;i<dim_x;i++) {
      argument =  e0_times_delta_t+g_times_delta_t*(psi[i]*psi[i]+psi[i+dim_x]*psi[i+dim_x]);
      wfc[i] = psi[i]*cos(argument)+psi[i+dim_x]*sin(argument);
      wfc[i+dim_x] = psi[i+dim_x]*cos(argument)-psi[i]*sin(argument);
    }
  }  
  return;
} 


""")

if __name__ == "__main__":
  ffibuilder.compile(verbose=True)

Answer 1

问题是用void __inline声明函数。我不完全确定为什么，但它似乎是在“强制内联”(编译后没有身体)和“非静态”(因此具有外部符号)的同时实现的。这可能是造成问题的原因。如果您移除__inline或在void __inline前面添加static，那么事情就会如愿以偿。如果你问一个C型的问题，你可能会得到更多的信息。