Default mode does not illustrate a spectre attack sometimes

[profolsen]

the if on line 31 succeeds if x is negative. This is a problem if the compiler puts secret at a lower address than array1, which is the case on my Mac (the offset calculation in main will make malicious_x and therefore x negative). In this case, the program doesn't actually demonstrate a spectre attack. The fix would be to check that x is both greater than or equal to zero and less than array1_size. I'm not sure how to do that without causing branching (I guess that using && must cause branching because of short-circuiting and will mess up branch prediction. Would something like "...int test = x < array1_size; test &= x >= 0; if(test) ..." work?).