Eclipse Luna CDT: What is a header variant?

问题

I am having difficulty getting the Eclipse Indexer (Codan) to recognize certain data declarations in header files. There is a new preference to Index all header variants, but little explanation as to what this means. Enabling the preference seems to fix the problem. But I still would like to know what the preference does exactly.

回答1:

Let's say you have header a.h like this:

#pragma once

#ifndef SYMBOL
#define SYMBOL int
#endif

struct S
{
  SYMBOL sym;
};

And now if you include your header like this:

struct UserSymbol
{
  int i, j, k;
};

#define SYMBOL UserSymbol

#include "a.h"

S var;

int main()
{
  var.sym.i = 123;
  return 0;
}

then Eclipse CDT may not to recognize sym.i.

You may have more complex examples with deeper nested inclusions or so on.

EDIT:

But if you include the a.h to the "Index all variants of specific headers" list or check "Index all header variants" Eclipse will build several variants of the a.h indexes and will "know" that you have defined the your specific SYMBOL.

来源：https://stackoverflow.com/questions/27217857/eclipse-luna-cdt-what-is-a-header-variant