That’s the surest way to nerd snipe some people. This code doesn’t work, and yet it does. After reading the commit history, it in fact never worked, and yet it has been up until yesterday. What in the actual fuck.
int bar;
...
foo()
{
if(bar) {
doX();
else
doY();
}
}
doY() had been broken for years but nobody ever set bar to be true; doX() was nevertheless being called. Setting bar to zero caused the buggy doY() to happen. Setting bar to one seemed to work, but would occasionally segfault.
Then someone explicitly initialized bar and got a linker error. Turns out in ye olden days of C, before "extern" was a thing there was a feature where variables that were initialized in no more than one compilation unit would be all coalesced by the linker. Before doY was broken, someone defined a function named bar, which then caused bar to have a non-zero (i.e. true) value. Someone later added some broken feature to "doY" and it passed all the tests because changing doY() didn't have any effect.
Double fuckup if the thing is backups and your data is gone. Reason why we check not only "does the backup job finished" but also "does the size looks right", because backup with 0 files still returns OK...