[cfe-commits] [PATCH] Thread-safety analysis: allow 'this' to be used as a valid lock expression

[Richard Smith]

Hi,

On Fri, January 13, 2012 22:39, Delesley Hutchins wrote:
> This patch modifies the thread safety analysis, so that 'this' can be
> used as a valid lock expression.

Using '0' to represent 'this' is a little subtle; I'd like to see a comment on
either MutexID or MutexID::DeclSeq calling this out. With that, LGTM.

One observation: this change breaks code which uses 'this->m' to name a mutex
which is a static data member (such a reference no longer matches against
naming the mutex as 'Class::m'). However, code which used 'p->m' was already
broken in this way, and the fix for that more general case should take care of
the 'this' case too, so I don't think that is an issue with this patch per se.
Testcases:

struct __attribute__((lockable)) S {
  static S *lock;
  static int n __attribute__((guarded_by(*lock)));
  int f() __attribute__((exclusive_locks_required(*this->lock))) {
    return n; // was accepted, now rejected
  }
  int g(S *p) __attribute__((exclusive_locks_required(*p->lock))) {
    return n; // rejected, should probably be accepted
  }
};

These may seem like strange ways to write such code, but the 'this->' form, at
least, might plausibly be used in templates.

- Richard