可以在C ++中使用可移植的方式使用命名属性来初始化POD结构吗？

struct A {
  unsigned int x;
};

// GCC: error: expected primary-expression before \'.\' token
A a = {
  .x = 0xdeadbeef;
};

// Clang: error: use of GNU old-style field designator extension [-Werror,-Wgnu-designator]
A a = {
  x : 0xdeadbeef;
};

A a = { 42 };

#if THIS_IS_GCC
  #define INIT_ATTR(x,y) x : y;
#elif THIS_IS_LLVM
  #define INIT_ATTR(x,y) .x=y;
#else
  #error Can\'t do it :/
#endif

A a = {
  INIT_ATTR(x,0xdeadbeef)
};

A a;
a.x = y;