Le 17/02/2011 19:29, Darren New nous fit lire :
> 
> Under what circumstances does it matter what order the members of a
> union are written in?  When does it make a difference as to which type
> inside the union is declared first?
> 
IBM extension: When you use zero-extent member in a union, it must be
the last "field".

e.g.

union Foo {
  int a;
  char b[0];
}

This syntax is supported by gcc too, but it does not care about the
order unless you want to initialise it. (for C99 and after)



typedef union {

  int a;
  long c;
  char b[0];

} Foo;

main()
{
	Foo k={257};
	printf("Hello %d %d\n",k.b[0],k.b[1]);
}


So, the first might not be always important (it is for initialisation at
declaration time), but the last would, on AIX at least.

Post a reply to this message