The challenge suffers from what I call a “chain of blunders”, where one blunder leads to another. Here are the exact details, in the traditional format.
The first who got close to the true nature of this bug was reader Shlomo who commented directly on the post, but I held back his comment in order not to spoil the fun for others. (Unfortunately, I couldn’t tell him, because he used a bogus email address—boo!). Christian Hujer, hacker extraordinaire, gave the most precise and extensive account on LinkedIn. While many found the blunder in the Makefile (Joe Nelson was the first), it was apparently such a good smokescreen that many people didn’t look any further. To me, the root blunder that started the chain of blunders is in the C language itself, which should have never allowed implicit zero-initialization of constants in the first place (which was corrected in C++).
Some believed that the preincrement of the loop-counter was the culprit as it would skip the first prime, but that’s not the case. The expression after the second semicolon gets evaluated always at the end of the loop body:
|
1 2 3 4 5 |
for (...; ...; <e>) { <body> } |
is equivalent to
|
1 2 3 4 5 6 |
for (...; ...;) { <body> <e>; } |
Substitute ++i or i++ for <e> — there’s no difference!
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