do while(false) pattern [duplicate]

Answer 1

It looks to me like it is only used for scoping rules, so that Lock<MutualExclusion> falls out of scope at the end of the block.

If that's the reason for it, then it's completely unnecesarry:

// some other code...
string s = "oh hai";
{
  Lock<MutualExclusion> lock(logMutex);
  // MAGIC HAPPENS
}
s = "oh bai";