Over the last few years I've repeatedly encountered an annoyance in my work projects. It's not a practical problem, you understand, merely a stylistic one. I mean, when the issue rears it's ugly head I pause, curse, write the code that works just fine but offends my sense of modern C++ idiom, and move on.
It's just that the issue lives rent-free in my head.
So here's the set up: I've spent the last six years upgrading my C++ skills to the "modern" era which means, amongst other things, preferring ranged for loops and routines from the algorithms header to explicit loops using indices, pointers or even iterators.1 Only my code has to interact with libraries and plugins written in C or exposing C-centric APIs, and those interactions often involve linked-lists. Which you can't put into ranged for loops or algorithms.
So, in my copious spare time, I set out to write a set of iterator templates that you can bolt-on to an arbitrary C linked list to support using modern C++ idioms with the list. That project is now approaching minimum-viable-product levels of completness, though there is a lot left to do.
1 That kind of preference is, of course, not absolute. Sometimes the old, explicit loops have some over-arching advantage and you use them without guilt.