What data structures and algorithms are not implementable in C? (stackoverflow.com)

What sprang to my mind is Jensen's Device: http://en.wikipedia.org/wiki/Jensen%27s_Device . This is a clever and little-known trick, that depends on pass-by-name semantics.

You cannot use negative structure displacements.

x86 and most architectures have negative displacements available.

In C, you cannot point to 128 bytes after the start and use negative byte displacements. Instead you must use DWORD displacements.

My compiler supports negative structure displacements.

    class MyStudent
    {
      $=-128;
      U8 name[120];
      U8 Address[120];
      U8 city[120];
    }

Name and address and city are byte displacements.