为什么Ada在从Rust接口调用时会卡在adainit上？

Question

快乐案例

我已经成功地在Ada中编译了一个最小的hello world窗口DLL，并通过FFI接口使用了它：

package MY_FFI is
    procedure Hello_World
        with
            Export => True,
            Convention => C,
            External_Name => "hello_world";
end MY_FFI;

package body MY_FFI is
    procedure Hello_World is
    begin
        Ada.Text_IO.Put_Line("Hello world!");
    end Send_Request;
end MY_FFI;

#[link(name = "my_ffi")]
extern "C" {
    #[link_name = "hello_world"]
    fn ada_hello_world();
    fn my_ffiinit(); // same as adainit just renamed by gprbuild
    fn my_ffifinal(); // same as adafinal just renamed by gprbuild
}

pub fn initialize_my_ffi() {
    unsafe {
        println!("step 1");
        my_ffiinit();
        println!("step 2");
        ada_hello_world();
        println!("step 3");
    }
}

其结果是：

step 1
step 2
Hello world!
step 3

真实问题

当我的Ada库变得更复杂并且需要以下额外的系统DLL时：

• libgnarl-7.dll
• libgnat-7.dll
• libgcc_s_seh-1.dll (明明POSIX)
• libwinpthreadthread-1.dll (明明POSIX)

我无法准确地挑出需要这些额外DLL的代码，但是一旦代码变得足够复杂到需要这些DLL，它就会在my_ffiinit函数的生锈处停下来，只输出：

step 1

同样的代码在x64 Linux上也能工作。另外，对其他Linux平台(powerpc、arm64)也进行交叉编译。

当我使用Library_Auto_Init="true"时，wine64输出：

0009:err:module:LdrInitializeThunk "libmy_ffi.dll" failed to initialize, aborting
0009:err:module:LdrInitializeThunk Initializing dlls for L"Z:\\test.exe" failed, status 20474343

主要项目探地雷达：

with "/opt/libA/a_lib.gpr";
with "/opt/libB/b_lib.gpr";

library project MY_FFI is
  for Languages    use ("Ada");
  for Library_Name use "my_ffi";
  for Library_Kind use "dynamic";
  for Library_Standalone use "encapsulated";
  for Source_Dirs  use ("src/**");
  for Library_Interface use (
    "my_ffi",
  );

  type Target_Type is ("windows64", "windows32", "linux64", "armhf", "powerpc", "arm64");
  Target : Target_Type := external ("target", "linux64");
  for Library_Dir use "lib/" & external ("target", "linux64");
  for Object_Dir   use  "obj/" & external ("target", "linux64");
end MY_FFI;

预编译共享库A的探地雷达

library project a_lib is
  for Languages    use ("Ada");
  for Library_Name use "a";
  for Library_Kind use "dynamic";
  for Source_Dirs  use ("src/**");

  type Target_Type is ("windows64", "windows32", "linux64", "armhf", "powerpc", "arm64");
  Target : Target_Type := external ("target", "linux64");
  for Library_Dir use "lib/" & external ("target", "linux64");
  for Object_Dir   use  "obj/" & external ("target", "linux64");

  package Naming is
      for Spec_Suffix ("ada") use ".ads";
      for Body_Suffix ("ada") use ".adb";
      for Separate_Suffix use ".adb";
      for Casing use "MixedCase";
      for Dot_Replacement use "-";
   end Naming;

  package Compiler is
    for Default_Switches ("ada") use ("-fPIC");
  end Compiler;

  for Externally_Built use "true";
end a_lib;

从资料来源汇编的B库探地雷达：

library project b_lib is
   for Source_Dirs use ("src");
   for Library_Name use "b";
   for Library_Dir use "lib";
   for Object_Dir use "obj";
   for Languages use ("Ada");

   package Compiler is
      for Switches ("ada") use ("-O2", "-ffunction-sections", "-gnatQ", "-fdata-sections", "-fPIC", "-gnatf", "-gnatwa");
   end Compiler;

   package Builder is
      for Switches ("ada") use ("-j0", "-k", "-s");
   end Builder;

   type Target_Type is ("windows64", "windows32", "linux64", "armhf", "powerpc", "arm64");
   Target : Target_Type := external ("target", "linux64");
   for Library_Dir use "lib/" & external ("target", "linux64");
   for Object_Dir   use  "obj/" & external ("target", "linux64");
end b_lib;

Answer 1

问题是在主项目配置文件中使用for Library_Standalone use "encapsulated";，当将其替换为默认值standard项目编译失败时，会出现以下错误：

shared library project "my_ffi" cannot import static library project "b"

一旦将行for Library_Kind use "relocatable";添加到库B项目配置中，编译错误就会消失，libmy_ffi.dll就会成功编译。更重要的是，当它从Rust调用时，产生的DLL可以正常工作。

仍未回答的怪癖：

• 为什么这对Linux平台来说不成问题呢？
• 为什么在编译项目时gprbuild不强制执行或警告唯一的静态策略

Answer 2

对Ada不太了解，但它不是有自己的ABI吗？这个文档建议您需要用Convention => C标记一个函数，以便从C调用它，类似于在Rust中使用extern "C"的方式。

Answer 3

会不会是在DLL:s中在库级别上创建任务？这是行不通的，因为动态库中的init代码在Windows上是严格单线程的。