Efficient linked list in C++?

Question

This document says std::list is inefficient:

std::list is an extremely inefficient class that is rarely useful. It performs a heap allocation

Answer 1

The requirement of not invalidating iterators except the one on a node being deleted is forbidding to every container that doesn't allocate individual nodes and is much different from e.g. list or map.
However, I've found that in almost every case when I thought that this was necessary, it turned out with a little discipline I could just as well do without. You might want to verify if you can, you would benefit greatly.

While std::list is indeed the "correct" thing if you need something like a list (for CS class, mostly), the statement that it is almost always the wrong choice is, unluckily, exactly right. While the O(1) claim is entirely true, it's nevertheless abysmal in relation to how actual computer hardware works, which gives it a huge constant factor. Note that not only are the objects that you iterate randomly placed, but the nodes that you maintain are, too (yes, you can somehow work around that with an allocator, but that is not the point). On the average, you have two one guaranteed cache misses for anything you do, plus up to two one dynamic allocations for mutating operations (one for the object, and another one for the node).

Edit: As pointed out by @ratchetfreak below, implementations of std::list commonly collapse the object and node allocation into one memory block as an optimization (akin to what e.g. make_shared does), which makes the average case somewhat less catastrophic (one allocation per mutation and one guaranteed cache miss instead of two).
A new, different consideration in this case might be that doing so may not be entirely trouble-free either. Postfixing the object with two pointers means reversing the direction while dereference which may interfere with auto prefetch.
Prefixing the object with the pointers, on the other hand, means you push the object back by two pointers' size, which will mean as much as 16 bytes on a 64-bit system (that might split a mid-sized object over cache line boundaries every time). Also, there's to consider that std::list cannot afford to break e.g. SSE code solely because it adds a clandestine offset as special surprise (so for example the xor-trick would likely not be applicable for reducing the two-pointer footprint). There would likely have to be some amount of "safe" padding to make sure objects added to a list still work the way they should.
I am unable to tell whether these are actual performance problems or merely distrust and fear from my side, but I believe it's fair to say that there may be more snakes hiding in the grass than one expects.

It's not for no reason that high-profile C++ experts (Stroustrup, notably) recommend using std::vector unless you have a really good reason not to.

Like many people before, I've tried to be smart about using (or inventing) something better than std::vector for one or the other particular, specialized problem where it seems you can do better, but it turns out that simply using std::vector is still almost always the best, or second best option (if std::vector happens to be not-the-best, std::deque is usually what you need instead).
You have way fewer allocations than with any other approach, way less memory fragmentation, way fewer indirections, and a much more favorable memory access pattern. And guess what, it's readily available and just works.
The fact that every now and then inserts require a copy of all elements is (usually) a total non-issue. You think it is, but it's not. It happens rarely and it is a copy of a linear block of memory, which is exactly what processors are good at (as opposed to many double-indirections and random jumps over memory).

If the requirement not to invalidate iterators is really an absolute must, you could for example pair a std::vector of objects with a dynamic bitset or, for lack of something better, a std::vector. Then use reserve() appropriately so reallocations do not happen. When deleting an element, do not remove it but only mark it as deleted in the bitmap (call the destructor by hand). At appropriate times, when you know that it's OK to invalidate iterators, call a "vacuum cleaner" function that compacts both the bit vector and the object vector. There, all unforeseeable iterator invalidations gone.

Yes, that requires maintaining one extra "element was deleted" bit, which is annoying. But a std::list must maintain two pointers as well, in additon to the actual object, and it must do allocations. With the vector (or two vectors), access is still very efficient, as it happens in a cache-friendly way. Iterating, even when checking for deleted nodes, still means you move linearly or almost-linearly over memory.