符号可见性与dllexport完全不同-主要原因是当您在Windows中的mingw/cygwin下编译.dll时，默认链接器的行为是选项-export-all-symbols-即默认情况下它将自动从您的.dll导出一切.

Symbol visibility is subtly different from dllexport - and the primary reason is that when you compile a .dll in Windows under mingw/cygwin, the default behaviour of the linker is the option -export-all-symbols - i.e. it will auto-export everything from your .dll by default.

您可以通过使用.def文件或将__declspec((dllexport))或__attribute((dllexport))放在 any 例程中来更改此行为(即，如果您指定要导出单个符号，则仅导出声明为已导出的符号).如果您的库中有很多符号，则可以在dll加载时显着提高性能.

You can change this behaviour by either using a .def file or putting either __declspec((dllexport)) or __attribute((dllexport)) on any routine (i.e. if you specify that a single symbol is to be exported then only the symbols that are declared exported are exported). This can have a significant performance improvement at dll load time if there are a lot of symbols in your library.

如果要使用等效的C++属性，请使用[[gnu::dllexport]]

If you want to use the equivalent C++ attribute, then you use [[gnu::dllexport]]

是的，请使用dllexport阻止.dll导出世界.

So yes, use dllexport to keep your .dll from exporting the world.

以类似的方式，您可以使用[[gnu:dllimport]]导入外部例程.

In a similar manner you can use [[gnu:dllimport]] for importing external routines.

在阅读文档时要小心；它的实际含义是，当您使用dllexport属性时，除非被覆盖，否则它还会触发visibility:default行为.

Careful while reading the documentation; what it actually says is that when you use the dllexport attribute, it also triggers the visibility:default behaviour unless it's overridden.