DllMain/DllMainCRTStartup 不在 DLL 中执行

Question

使用 gnat 构建的 DLL 中的初始化代码在导入时不会自动运行ning。我做了一个 MCVE，包括：

division.ads

with System;
with Interfaces.C;

package Division is
   --Neither of these work
   procedure DllMainCRTStartup ;
   pragma Export (StdCall, DllMainCRTStartup , "DllMainCRTStartup"); --Edited as noticed by Brian
   -- procedure DllMain
   -- pragma Export (StdCall, DllMain , "DllMain ");

   function Div (A : in INTEGER; B : in INTEGER) return INTEGER;
   pragma Export (C, Div, "MyDivision");

   -- --If I put this, it does not compile... maybe a wrong linkage option set?
   -- procedure AdaInit; 
   -- pragma Import (C, AdaInit, "adainit");
end Division;

division.adb

with text_io;

package body Division is
   procedure DllMainCRTStartup  is begin --DllMain or DllMainCRTStartup
      text_io.put("INIT CODE YEAH!!!*************!"); --This does not execute :(
      --AdaInit;
   end DllMainCRTStartup ;

   function Div(A : in INTEGER; B : in INTEGER) return INTEGER is
      X : INTEGER := A/B;
   begin
      return X;
   end Div;
end Division;

和 gpr:

library project Proj_Name is
  for Library_Name use "math";
  for Object_Dir use "obj";
  for Source_Dirs use ("src");
  for Library_Dir use "lib";
  for Library_Interface use ("Division");
  for Library_Kind use "dynamic";
  for Library_Options use ("-LC:\GNAT15\lib\gcc\i686-pc-mingw32.9.3\adalib",
                           "-LC:\GNAT15\lib\gcc\i686-pc-mingw32.9.3\adalib\libgnat");
end Proj_Name;

我正在使用 ctypes 测试来自 python 的 dll。我用 ctypes.CDLL 导入它，我可以使用 MyDivision。然而，初始化代码在导入dll时不会运行，因为text_io没有被执行。

另一方面，如果我将 AdaInit 过程添加到代码中，我在编译时会得到类似这样的结果：

undefined reference to `adainit'

非常感谢！

Answer 1

我不确定你是怎么知道初始化代码不是运行?

我在 macOS 上运行ning，但 Ada 方面应该是相似的。我写这个包 spec/body 作为你的更简单的版本：

package Division is

   function Div (A : in INTEGER; B : in INTEGER) return INTEGER;
   pragma Export (C, Div, "MyDivision");

end Division;

with Ada.Text_IO;
package body Division is

   function Div(A : in INTEGER; B : in INTEGER) return INTEGER is
      X : INTEGER := A/B;
   begin
      return X;
   end Div;

   procedure Test_For_Elaboration is
   begin
      Ada.Text_IO.Put_Line ("hello world!");
   end Test_For_Elaboration;

begin
   Test_For_Elaboration;
end Division;

有了这个更简单的 GPR

library project Proj_Name is
  for Library_Name use "math";
  for Object_Dir use "obj";
  for Source_Dirs use ("src");
  for Library_Dir use "lib";
  for Library_Interface use ("Division");
  for Library_Kind use "dynamic";
end Proj_Name;

并使用此 C 代码进行测试：

#include <stdio.h>

extern int MyDivision(int, int);

int main()
{
  printf("42 / 2 => %d\n", MyDivision(42, 2));
  return 0;
}

结果是

$ ./caller 
hello world!
42 / 2 => 21

很明显，对我来说，库的阐述是调用的，我什么都不用做。

原因是您在项目文件中指定了 Library_Interface，这意味着您正在构建一个 stand-alone library，

is a library that contains the necessary code to elaborate the Ada units that are included in the library. A stand-alone library is a convenient way to add an Ada subsystem to a more global system whose main is not in Ada since it makes the elaboration of the Ada part mostly transparent.

您可以指定一个不自动初始化的独立动态库，使用

for Library_Auto_Init use "false";

这种情况需要自己调用库的初始化过程；它叫做 {library-name}init（在你的例子中，mathinit）。但是你需要从你的主程序中调用它；它需要在 C

中声明

extern void mathinit();

DllMain/DllMainCRTStartup 不在 DLL 中执行

DllMain/DllMainCRTStartup does not execute in DLL

dll

ada

gnat