[Bug libstdc++/58338] New: Add noexcept to functions with a narrow contract

["glisse at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58338

            Bug ID: 58338
           Summary: Add noexcept to functions with a narrow contract
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: glisse at gcc dot gnu.org

Hello,

the standard only requires a noexcept specifier on functions with a wide
contract, to allow some debug implementations of functions with a narrow
contract. However, it also explicitly gives permission to strengthen the
exception specification of non-virtual functions. I believe libstdc++ should
add noexcept whereever it can, since this is supposed to help with performance.

Functions like vector::front seem like good candidates. I wouldn't mind if the
debug version had a different exception specification, but that doesn't even
seem necessary since libstdc++ aborts instead of throwing.

https://groups.google.com/a/isocpp.org/d/msg/std-discussion/lkRyImxouC0/kZpWqI0MjXsJ