在Visual Studio中编译gcc代码会导致错误C3646：'__attribute__'：未知重写说明符 [英] Compiling gcc code in Visual Studio causes error C3646: '__attribute__': unknown override specifier

问题描述

错误C3646：'__attribute__'：未知的重写说明符

代码：

  LEMUR_PREALIGN char _stack [sizeof（_Type）* _Count] LEMUR_POSTALIGN; 
  

完成错误：

<1> c：\program files\indri\indri 5.9\include\indri\greedy_vector（52）：error C3646：'__attribute__'：未知覆盖说明符

其他信息：我正在尝试在Visual Studio项目中使用indri.lib。

解决方案

__属性__ 命令是gcc的编译器特定命令。它用于此文件的第52行与 （（align））命令，其中：

指定指定类型变量的最小对齐（以字节为单位）

Visual studio实际上有一个类似的对齐命令： align 。但有两个问题：
$ b

1. __ declspec（align（＃））不会支持默认行为： __ attribute__（（aligned））
   

   将一个类型与您正在编译的目标机器的最大有用对齐关联
   

   
   
   

   
   
   2. __ declspec（align（＃））是一个前缀。 __属性__（（aligned（＃）））是后缀。这意味着您的实际代码需要在展示位置上有所不同：
   
   

   struct S {short f [3 ]。 } __attribute__（（aligned））; // gcc对齐定义
__declspec（align（16））strict S {short f [3]; }; // MSVC alignment

   
   
   

   这里的要点是你可能会更好 #ifdef __ attribute__（（aligned））并烹饪您自己的 __ declspec（align（＃））。

   
   
   

   更多信息请参阅： GCC vs MSVC class packing and alignment
   
   

   ---

   
   
   

   经过对lemur_platform的更多研究。看起来代码已经完成了所有上述工作！您会注意到 #define LEMUR_POSTALIGN __attribute__（（aligned））被封装在 #ifndef WIN32 中。所以你需要做的是在你的Visual Studio项目中定义 WIN32 ！

   
   

   I am getting the following error:

   error C3646: '__attribute__': unknown override specifier

   Code:

   LEMUR_PREALIGN char _stack[ sizeof(_Type) * _Count ] LEMUR_POSTALIGN;
   

   Complete error:

   1>c:\program files\indri\indri 5.9\include\indri\greedy_vector(52): error C3646: '__attribute__': unknown override specifier

   Additional info: I am trying to use indri.lib in Visual Studio project.

   解决方案

   The __attribute__ command is a compiler specific command to gcc. And it is used on line 52 of this file with the ((align)) command, which:

   Specifies a minimum alignment (in bytes) for variables of the specified type

   Visual studio does in fact have a similar alignment command: align. But there are two problems:

   1. __declspec(align(#)) does not support the defaulted: __attribute__ ((aligned)) behavior which will:

   Align a type to the maximum useful alignment for the target machine you are compiling for

   2. __declspec(align(#)) is a prefix. __attribute__((aligned(#))) is a suffix. This means that your actual code would need to differ on the placement:

   struct S { short f[3]; } __attribute__ ((aligned)); // gcc alignment definition __declspec(align(16)) strict S { short f[3]; }; // MSVC alignment

   The point here is you'd probably be better off #ifdefing by compiler any line that uses __attribute__ ((aligned)) and cooking your own __declspec(align(#)).

   For more info see: GCC vs MSVC class packing and alignment

   ---

   After a bit more study into lemur_platform.h it looks like the code has already done all the above work for you! You'll notice that #define LEMUR_POSTALIGN __attribute__ ((aligned)) is wrapped in an #ifndef WIN32. So what you need to do is define WIN32 in your Visual Studio project!

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