do while(false) pattern [duplicate]

Answer 1

It turns a block into a single statement. If you just use a block (i.e. code enclosed in {}) strange things can happen, for example

#define STUFF() \
  { do_something(); do_something_else(); }

if (cond)
    STUFF();
else
    //...

the extra semi-colon breaks the syntax. The do {} while(false) instead is a single statement.

You can find more about this and other macro tricks here.