GCC声明：typedef __pid_t pid_t？ [英] GCC declarations: typedef __pid_t pid_t?

问题描述

我对（例如）pid_t的声明感到困惑。 __pid_t是什么意思？它是在别处定义的另一种类型吗如果是，在哪里？为什么我的types.h在ubuntu 13.04 64bit中定义了pid_t就像这样：

  #ifndef __pid_t_defined 
 typedef __pid_t pid_t; 
 #define __pid_t_defined 
 #endif 
  

而不是像

  typedef int pid_t; 
  

我看到一些网站拥有types.h头文件，并且声明是最后一种方式。这是一个：
http://www.sde.cs.titech.ac.jp/~gondow /dwarf2-xml/HTML-rxref/app/gcc-3.3.2/lib/gcc-lib/sparc-sun-solaris2.8/3.3.2/include/sys/types.h.html

更新：

好的，我发现pid_t是__pid_t，它是__PID_T_TYPE，它是__S32_TYPE这是一个int。我现在的问题是这是为什么？ POSIX只声明pid_t必须是一个有符号的整数，所以为什么声明在头文件中输入太深？

解决方案

好的，我发现__pid_t表示这个问题的答案：

/ p>

QUOTE

  typedef __pid_t pid_t; 
 ... 
＃define __STD_TYPE typedef 
 __STD_TYPE __PID_T_TYPE __pid_t; / *进程标识的类型。 * / 
 ... 
 #define __PID_T_TYPE __S32_TYPE 
 ... 
 #define __S32_TYPE int 
  

UNQUOTE

所以pid_t是__pid_t，它是一个__PID_T_TYPE，它是一个__S32_TYPE，它是一个int。

I am confused about the declaration of (for example) pid_t. What does __pid_t mean? Is it another type defined elsewhere? If yes, where? Why is my types.h in ubuntu 13.04 64bit defining pid_t like:

#ifndef __pid_t_defined
typedef __pid_t pid_t;
#define __pid_t_defined
#endif

and not something like

typedef int pid_t;

I saw some websites that have types.h headers with the declaration done the last way. This is one: http://www.sde.cs.titech.ac.jp/~gondow/dwarf2-xml/HTML-rxref/app/gcc-3.3.2/lib/gcc-lib/sparc-sun-solaris2.8/3.3.2/include/sys/types.h.html

UPDATE:

Ok I found out that a pid_t is an __pid_t which is an __PID_T_TYPE which is which is an __S32_TYPE which is an int. My question now is why is this? POSIX only states that pid_t has to be a signed integer, so why make the declaration enter soo deep in header files?

解决方案

Ok I found what the __pid_t means on the answer to this question: Why PID of a process is represented by opaque data type?

QUOTE

typedef __pid_t pid_t;
...
# define __STD_TYPE     typedef
__STD_TYPE __PID_T_TYPE __pid_t;    /* Type of process identifications.  */
...
#define __PID_T_TYPE        __S32_TYPE
...
#define __S32_TYPE      int

UNQUOTE

So pid_t is an __pid_t which is an __PID_T_TYPE which is which is an __S32_TYPE which is an int.

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