Re: Unhealthy commit e3340714c8 Style: clarify "do nothing" macro with {};

[Graham Percival]

On Thu, Oct 7, 2010 at 8:36 PM, David Kastrup <address@hidden> wrote:
>
> -#define ASSERT_LIVE_IS_ALLOWED()
> +#define ASSERT_LIVE_IS_ALLOWED() {};
>
> The problem is that the replaced statement defines
> ASSERT_LIVE_IS_ALLOWED() as being 1, while the second defines it as {};.

> That is a particular bad idea for things like
>
> if (condition) ASSERT_LIVE_IS_ALLOWED(); else ...

My understanding was that this is a debugging construct which is only
used as a function call.  I mean, the "non-else" definition of
ASSERT_LIVE would also run into problems in that construct:

#ifndef NDEBUG
#define ASSERT_LIVE_IS_ALLOWED()     \
  static bool passed_here_once;\
  if (parsed_objects_should_be_dead && !passed_here_once) { \
    ::programming_error (string ("Parsed object should be dead: ")  +
__PRETTY_FUNCTION__ ); \
    passed_here_once = true;\
  }
#else
#define ASSERT_LIVE_IS_ALLOWED() {};
#endif

in that the macro might look like a single statement, but it gets
expanded into two.  (is it worth enclosing the non-else definition
with a { } to avoid this?)


> So either ASSERT_LIVE_IS_ALLOWED() should be explicitly defined as 1.

I'm fine with that change, if it makes sense given the non-else
definition.  I'm kind-of out of my depth here.

Cheers,
- Graham