警告 C4090:“正在初始化":不同的“__unaligned"限定符 [英] warning C4090: 'initializing': different '__unaligned' qualifiers

问题描述

 void file_explore(std::wstring str) {
     ITEMIDLIST *pIDL = ILCreateFromPath(str.c_str());
     if ( NULL != pIDL ) {
         SHOpenFolderAndSelectItems(pIDL , 0 , 0 , 0);
         ILFree(pIDL);
     } else {
         std::wstring p = str.substr(0 , str.find_last_of('\\'));
         ShellExecute(NULL , L"explore" , p.c_str() , NULL , NULL , SW_SHOWNORMAL);
     }
 }    

以上编译 32 位时没有警告，但使用 64 位时我收到警告 c4090 但是文档:https://msdn.microsoft.com/en-us/library/k77bkb8d.aspx 声明这是交流错误，我将获得 C2440 for c++，但我正在使用 c++.

The above compiles without warning for 32bit but with 64bit I get warning c4090 however the docs: https://msdn.microsoft.com/en-us/library/k77bkb8d.aspx state that this is a c error and I will get C2440 for c++ yet I'm using c++.

抱怨的代码行是:

 ITEMIDLIST *pIDL = ILCreateFromPath(str.c_str());

如何解决 64 位版本的这个问题?

How to fix this issue for 64bit builds?

推荐答案

LPITEMIDLIST 被定义为 typedef ITEMIDLIST __unaligned *LPITEMIDLIST，所以接受结果为 ITEMIDLIST* 失去了 __unaligned 修饰符.我不确定这与 32 位和 64 位有何关系.

LPITEMIDLIST is defined as typedef ITEMIDLIST __unaligned *LPITEMIDLIST, so accepting the result as ITEMIDLIST * loses that __unaligned modifier. I am not sure how this relates to 32-bit versus 64-bit.

正如 Hans Passant 评论的那样，使用 typedef 解决了这个问题.就我而言，我使用的是 std::unique_ptr，它需要基类型而不是指针，所以我需要一个非指针 typedef.因为它可能对偶然发现这个答案的人有切切的兴趣，所以我将介绍我如何使用 std::unique_ptr 和 ILCreateFromPath，包括自定义删除者的乐趣:

As Hans Passant commented, using the typedef solves the issue. In my case, I'm using std::unique_ptr, which wants the base type rather than the pointer, so I needed a non-pointer typedef. Because it might be of tangential interest for people stumbling upon this answer, I'll put in how I am making use of a std::unique_ptr with ILCreateFromPath, including the custom deleter for fun:

auto deleter = [](LPITEMIDLIST ptr) { ILFree(ptr); };
using itemidlistptr_t = std::unique_ptr<
    std::remove_ptr_t<LPITEMIDLIST>, decltype(deleter)>;
auto dir = itemidlistptr_t(ILCreateFromPathW(folder.c_str()), deleter);

使用 std::remove_pointer_t 有点绕，但我喜欢这里而不是直接提到 __unaligned 自己.

Using std::remove_pointer_t is a bit roundabout, but I like it here rather than mentioning __unaligned myself directly.

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