RFR: 8334868: Ensure CheckUninstallModalHook is called in WPageDialogPeer._show

[Alexey Ivanov]

On Thu, 27 Jun 2024 11:26:24 GMT, Julian Waters <jwaters at openjdk.org> wrote:

> …I believe I was referring to the use of C++'s std::unique_ptr, which has the functionality for cleanup that we need.

Yes, `std::unique_ptr` could be useful for handling automatic deallocation of objects created with the `new` operator.

It won't help with releasing references to Java objects though.

> That is currently blocked by awt.dll not being allowed to use the C++ Standard Library, but if one looks at the current awt.dll with dumpbin, awt.dll is actually already is linked to msvcp.dll, meaning it already uses C++ Standard Library somehow (I don't know what exactly makes it dependent on msvcp.dll)

I remember STL has been banned from AWT code, yet I don't know the reasons for it. It could be to keep the size smaller.

I can see that `awt.dll` depends on `msvcp140.dll` and imports one function from it: `?_Xlength_error at std@@YAXPEBD at Z`. It doesn't look like the C++ Standard Library is used. I can't find where it comes from though… It could be worth getting rid of this dependency.

I built a small sample app which uses `std::unique_ptr` and `std::make_unique` and it does not depend on `msvcp140.dll` at all. This makes sense, template libraries are header-only and will become part of the executable (or the dynamic library).

The only references to `std` namespace that I found in client are in `ShellFolder.cpp` which uses `std::bad_alloc`, it uses this type in `catch` blocks and it may throw an object of this class.

So, it looks `awt.dll` doesn't use the C++ Standard Library.

However, using C++ objects with [RAII](https://en.wikipedia.org/wiki/Resource_acquisition_is_initialization) makes the code shorter and frees the programmer from repeating clean-up blocks¹.

Indeed, it's already used by C++ classes in AWT: [`JNILocalFrame`](https://github.com/openjdk/jdk/blob/79a23017fc7154738c375fbb12a997525c3bf9e7/src/java.desktop/windows/native/libawt/windows/awt_Toolkit.h#L64-L77) and [`CriticalSection`](https://github.com/openjdk/jdk/blob/79a23017fc7154738c375fbb12a997525c3bf9e7/src/java.desktop/windows/native/libawt/windows/awt_Toolkit.h#L85-L119) along with its `Lock` class inside.

¹ Repeated clean-up blocks can be seen in #18584 in nearly all the files.

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PR Comment: https://git.openjdk.org/jdk/pull/19867#issuecomment-2194603793