Re: [Xen-devel] [PATCH] Use new Xen public header for product numbers and names

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Paul Durrant writes ("RE: [Xen-devel] [PATCH] Use new Xen public header for 
product numbers     and names"):
> Ok. I'll come up with something we can use to define an array and
> then we can iterate over that.

Great.


What do people think of this preprocessor approach, which I suggested
earlier:

  #define PVDRIVERS_LIST(EACH)                              \
    EACH(WINDOWS, 0x0001 /* Citrix */, "xensource-windows") \
    ...

That can be used to generate arrays, or switch statements, or
whatever.  For example in pvdrivers.h:

  #define PVDRIVERS_EACH_ENUM(name,num,string) \
      PVDRIVERS_ID_##name = num,
  enum {
      PVDRIVERS_LIST(PVDRIVERS_EACH_ENUM)
  };

and then in qemu:

  #define PVDRIVERS_EACH_SWITCH(name,num,string) \
     case PVDRIVERS_ID_##name:  product = string;  break;

  switch (id) {
  PVDRIVERS_LIST(PVDRIVERS_EACH_SWITCH)
  default:
    sprintf blah blah
  }


If the indirect macro trick is too abstruse it's also possible to do
this:

  #define PVDRIVERS_LIST                                              \
    PVDRIVERS_EACH(WINDOWS, 0x0001 /* Citrix */, "xensource-windows") \
    ...

That can be used to generate arrays, or switch statements, or
whatever.  For example in pvdrivers.h:

  #define PVDRIVERS_EACH(name,num,string) \
      PVDRIVERS_ID_##name = num,
  enum {
      PVDRIVERS_LIST
  };
  #undef PVDRIVERS_EACH

and then in qemu:

  #define PVDRIVERS_EACH(name,num,string) \
     case PVDRIVERS_ID_##name:  product = string;  break;

  switch (id) {
  PVDRIVERS_LIST
  default:
    sprintf blah blah
  }

  #undef PVDRIVERS_EACH


A #define containing an array initialiser is the other obvious
alternative although of course the macro-based approaches I sketch
above can be used to define arrays but not vice versa.


Ian.

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