D has an optional Garbage Collector. It is optional in that it can be disable or its function calls can be stubbed out. However many language features expect a garbage collector and should be avoid while it is disabled.
- Do not resize arrays, including concatenation.
- Do not use the associative arrays.
- Do not make use of closures.
- Do not use 'new' to create objects.
- Phobos and Tango generally assume a usable GC.
Garbage Collection Workgroup for progress on improving the GC performance.