Revert. IF is a macro, if is a conditional statement. Furthermore, casting to an unsigned 32 bit integer on a 64 bit machine causes the the x<0 to always be false. But since there is a comma, the "bad integer" was evaluating to a nonzero address and so the conditional was always true and the empty statement would be executed. That is wrong.

stepmania/src/lua-5.1/src/lundump.c

@@ -67,7 +67,7 @@ static int LoadInt(LoadState* S)
  LoadVar(S,x);
  if (S->flip)
   x = Swap32(x);
- if ((uint32_t)x<0, "bad integer");
+ IF ((int32_t)x<0, "bad integer");
  return x;
 }