[Bug c++/79950] G++ cannot detect simple off by one error in STL classes

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79950

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The two cases are not equivalent, because the bounds of a[10] are known at
compile-time, but v.size() is not. The only way to know v.size() is with a
run-time check, which has a non-zero cost.