Delphi7 call C DLL suggest AV errors-CodePudding

 unit Unit1; 

Interface 

USES the 
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, 
StdCtrls; 

Type 
TForm1=class (TForm) 
For: TButton; 
Edit1: TEdit; 
Edit2: TEdit; 
Edit3: TEdit; 
Label1: TLabel; 
Label2: TLabel; 
Procedure Button1Click (Sender: TObject); 
Private 
{Private declarations} 
Public 
{Public declarations} 
end; 

The function to the Add (a: Integer; B: Integer) : Integer; Stdcall; External 'Dll1. DLL'; 

Var 
Form1: TForm1; 

Implementation 

{$R *. DFM} 

Procedure TForm1. Button1Click (Sender: TObject); 
The begin 
Edit1. Text:=IntToStr (Add (3, 6));//this is why the failure? 

//Edit3. Text:=IntToStr (Add (StrToInt (Edit1. Text), StrToInt (Edit2. Text)));//this success 
end; 

End.

The code above
Is the simple addition, don't know why the first kind of writing is wrong, the second will have no matter son, bosses, please explain, thanks

//PCH. H: is this the precompiled header files, 
//the files listed below are compiled only once, and improve the performance of the future generation to generate, 
//this will also affect the performance of IntelliSense, including code completion and many browsing, 
//but if any of the files listed here in the generated between the update, all of them will be recompiled, 
//do not add to frequently updated files here, this will enable performance advantage is invalid, 

# # ifndef PCH_H 
# define PCH_H 

Extern "C" _declspec (dllexport) int the Add (int a, int b); 
Extern "C" _declspec (dllexport) int Sub (int a, int b); 

//add to precompiled header here 
# include "framework. H" 

# endif//PCH_H

//PCH. CPP: with the precompiled header corresponding source file 

# include "PCH. H" 

//when using precompiled header, you need to use the source files, compiling to succeed, 
Int the Add (int a, int b) 
{
return a + b; 
} 

Int Sub (int a, int b) 
{
Return a - b; 
}

CodePudding user response:

Know why, the c + + default cdecl calling way, keyword cdecl in Delphi call also use to call
The function to the Add (a: Integer; B: Integer) : Integer; Cdecl; External 'Dll1. DLL';

Or changing the c + + to stdcall calling way line

Reference:
https://www.cnblogs.com/jiftle/p/8451336.html
https://blog.csdn.net/sss_369/article/details/87473329

CodePudding user response:

Top you ~

CodePudding user response:

So,