_Generic在C11中的语法和示例用法

我听说C11添加了泛型。我已经用Google搜索了一下，看了一些文章，了解到有一个新的关键字（_Generic）等等。但我似乎无法掌握所有内容。

它类似于C＃中的泛型或C ++中的模板吗？谁能给我关于C11泛型定义，其语法和简单示例用法示例的简短说明？

这是一个很好的介绍。这是概述：

通用选择是通过新关键字_Generic实现的。语法类似于类型的简单switch语句：_Generic( 'a', char: 1, int: 2, long: 3, default: 0) 取值为2（字符常量在C中为int）。

基本上，它的工作方式类似于的switch，其中标签是类型名称，将根据第一个表达式的类型（'a'上述）进行测试。结果成为评估的结果_Generic()。

我看到的最好的例子启发了以下（可运行的）示例，该示例为破解内省开辟了各种奇特的可能性...

#include <stdio.h>
#include <stddef.h>
#include <stdint.h>

#define typename(x) _Generic((x),        /* Get the name of a type */             \
                                                                                  \
        _Bool: "_Bool",                  unsigned char: "unsigned char",          \
         char: "char",                     signed char: "signed char",            \
    short int: "short int",         unsigned short int: "unsigned short int",     \
          int: "int",                     unsigned int: "unsigned int",           \
     long int: "long int",           unsigned long int: "unsigned long int",      \
long long int: "long long int", unsigned long long int: "unsigned long long int", \
        float: "float",                         double: "double",                 \
  long double: "long double",                   char *: "pointer to char",        \
       void *: "pointer to void",                int *: "pointer to int",         \
      default: "other")

#define fmt "%20s is '%s'\n"
int main() {

  size_t s; ptrdiff_t p; intmax_t i; int ai[3] = {0}; return printf( fmt fmt fmt fmt fmt fmt fmt fmt,

     "size_t", typename(s),               "ptrdiff_t", typename(p),     
   "intmax_t", typename(i),      "character constant", typename('0'),
 "0x7FFFFFFF", typename(0x7FFFFFFF),     "0xFFFFFFFF", typename(0xFFFFFFFF),
"0x7FFFFFFFU", typename(0x7FFFFFFFU),  "array of int", typename(ai));
}

                 ╔═══════════════╗ 
═════════════════╣ Amazeballs... ╠═════════════════════════════════════
                 ╚═══════════════╝ 
            size_t is 'unsigned long int'
         ptrdiff_t is 'long int'
          intmax_t is 'long int'
character constant is 'int'
        0x7FFFFFFF is 'int'
        0xFFFFFFFF is 'unsigned int'
       0x7FFFFFFFU is 'unsigned int'
      array of int is 'other'

我使用的是clion 1.2.4，而clion现在不支持c11，因此我在c99中使用以下代码而不是_Generic

#include <stdio.h>

int main(int argc, char **argv) {
    char *s;
    if (__builtin_types_compatible_p(__typeof__(s), long)) {
        puts("long");
    } else if (__builtin_types_compatible_p(__typeof__(s), char*)) {
        puts("str");
    }
    return (0);
};