在 Delphi 中使用 C++ .DLL 中的函数

Question

我正在尝试从 Delphi 中的“近似最近邻居”(ANN) 库中访问各种函数（实际上，它是 Lazarus/FreePascal，但这应该无关紧要）。

这是 C++ 中的减速：

#include <cstdlib>                      // C standard lib defs
#include <ANN/ANNx.h>                   // all ANN includes
#include <ANN/ANNperf.h>                // ANN performance 

using namespace std;                    // make std:: accessible
....
....
void annMaxPtsVisit(            // set limit on max. pts to visit in search
    int                 maxPts)         // the limit
{
    ANNmaxPtsVisited = maxPts;
}

这是我从 Lazarus 中访问 annMaxPtsVisit 函数的尝试（如果您不知道 Lazarus 是什么，请假装它的 delphi）：

unit unit1;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, StdCtrls;
type

  { TForm1 }

  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
    procedure annMaxPtsVisit(input:Integer); stdcall;
  private

    { private declarations }
  public
    { public declarations }

  end;

var
  Form1: TForm1;

implementation

{$R *.lfm}
{ TForm1 }
procedure TForm1.annMaxPtsVisit(input: Integer); stdcall; external 'ANN.dll' name 'annMaxPtsVisit';

procedure TForm1.Button1Click(Sender: TObject);
begin
           annMaxPtsVisit(10);
end;

end.

程序可以编译，但是当我尝试执行它时，我收到一条错误消息：

“无法在动态链接库ANN.dll中定位程序入口点anMaxPtsVisit”

如果有人能帮我解决这个问题，我将不胜感激。

以下是 DLL 的导出：

class ANNsampStat ann_average_err   
class ANNsampStat ann_rank_err  
const ANNbd_tree::`vftable' 
const ANNbruteForce::`vftable'  
const ANNkd_tree::`vftable' 
const ANNpointSet::`vftable'    
double * * __cdecl annAllocPts(int,int) 
double * __cdecl annAllocPt(int,double) 
double * __cdecl annCopyPt(int,double *)    
double __cdecl annDist(int,double *,double *)   
protected: void __thiscall ANNkd_tree::SkeletonTree(int,int,int,double * *,int *)   
public: __thiscall ANNbd_tree::ANNbd_tree(class ANNbd_tree const &) 
public: __thiscall ANNbd_tree::ANNbd_tree(class std::basic_istream<char,struct std::char_traits<char> > &)  
public: __thiscall ANNbd_tree::ANNbd_tree(double * *,int,int,int,enum ANNsplitRule,enum ANNshrinkRule)  
public: __thiscall ANNbd_tree::ANNbd_tree(int,int,int)  
public: __thiscall ANNbruteForce::ANNbruteForce(class ANNbruteForce const &)    
public: __thiscall ANNbruteForce::ANNbruteForce(double * *,int,int) 
public: __thiscall ANNkd_tree::ANNkd_tree(class ANNkd_tree const &) 
public: __thiscall ANNkd_tree::ANNkd_tree(class std::basic_istream<char,struct std::char_traits<char> > &)  
public: __thiscall ANNkd_tree::ANNkd_tree(double * *,int,int,int,enum ANNsplitRule) 
public: __thiscall ANNkd_tree::ANNkd_tree(int,int,int)  
public: __thiscall ANNpointSet::ANNpointSet(class ANNpointSet const &)  
public: __thiscall ANNpointSet::ANNpointSet(void)   
public: __thiscall ANNsampStat::ANNsampStat(void)   
public: class ANNbd_tree & __thiscall ANNbd_tree::operator=(class ANNbd_tree const &)   
public: class ANNbruteForce & __thiscall ANNbruteForce::operator=(class ANNbruteForce const &)  
public: class ANNkd_tree & __thiscall ANNkd_tree::operator=(class ANNkd_tree const &)   
public: class ANNpointSet & __thiscall ANNpointSet::operator=(class ANNpointSet const &)    
public: class ANNsampStat & __thiscall ANNsampStat::operator=(class ANNsampStat const &)    
public: double __thiscall ANNsampStat::max(void)    
public: double __thiscall ANNsampStat::mean(void)   
public: double __thiscall ANNsampStat::min(void)    
public: double __thiscall ANNsampStat::stdDev(void) 
public: int __thiscall ANNsampStat::samples(void)   
public: virtual __thiscall ANNbd_tree::~ANNbd_tree(void)    
public: virtual __thiscall ANNbruteForce::~ANNbruteForce(void)  
public: virtual __thiscall ANNkd_tree::~ANNkd_tree(void)    
public: virtual __thiscall ANNpointSet::~ANNpointSet(void)  
public: virtual double * * __thiscall ANNbruteForce::thePoints(void)    
public: virtual double * * __thiscall ANNkd_tree::thePoints(void)   
public: virtual int __thiscall ANNbruteForce::annkFRSearch(double *,double,int,int *,double *,double)   
public: virtual int __thiscall ANNbruteForce::nPoints(void) 
public: virtual int __thiscall ANNbruteForce::theDim(void)  
public: virtual int __thiscall ANNkd_tree::annkFRSearch(double *,double,int,int *,double *,double)  
public: virtual int __thiscall ANNkd_tree::nPoints(void)    
public: virtual int __thiscall ANNkd_tree::theDim(void) 
public: virtual void __thiscall ANNbruteForce::annkSearch(double *,int,int *,double *,double)   
public: virtual void __thiscall ANNkd_tree::annkSearch(double *,int,int *,double *,double)  
public: virtual void __thiscall ANNkd_tree::Dump(enum ANNbool,class std::basic_ostream<char,struct std::char_traits<char> > &)  
public: virtual void __thiscall ANNkd_tree::getStats(class ANNkdStats &)    
public: virtual void __thiscall ANNkd_tree::Print(enum ANNbool,class std::basic_ostream<char,struct std::char_traits<char> > &) 
public: void __thiscall ANNkd_tree::`default constructor closure'(void) 
public: void __thiscall ANNkd_tree::annkPriSearch(double *,int,int *,double *,double)   
public: void __thiscall ANNsampStat::operator+=(double) 
public: void __thiscall ANNsampStat::reset(void)    
void __cdecl annClose(void) 
void __cdecl annDeallocPt(double * &)   
void __cdecl annDeallocPts(double * * &)    
void __cdecl annMaxPtsVisit(int)    
void __cdecl annPrintStats(enum ANNbool)    
void __cdecl annResetCounts(void)   
void __cdecl annResetStats(int) 
void __cdecl annUpdateStats(void)   

Answer 1

也许按索引导入有效：

procedure annMaxPtsVisit(input: Integer); stdcall; external 'ANN.dll' index 39;

（这是通过Dependecy Walker得到的索引）

您可能需要更改为 cdecl 调用约定，具体取决于 DLL 的构建方式：

procedure annMaxPtsVisit(input: Integer); cdecl; external 'ANN.dll' index 39; // could work

编辑：看起来cdecl 是正确的做法，查看您添加的导出。

Edit2：Dependency walker 还显示修饰名称，正如 @user786653 所怀疑的那样。这似乎也有效：

procedure annMaxPtsVisit(input: Integer); cdecl; external 'ANN.dll' Name '?annMaxPtsVisit@@YAXH@Z';

不过看起来很丑。

Answer 2

首先将annMaxPtsVisit声明为普通过程，而不是TForm1方法：

procedure annMaxPtsVisit(input: Integer); stdcall; external 'ANN.dll';