The Boehm-Demers-Weiser conservative garbage collector can be used as a garbage collecting replacement for C malloc or C++ new. It allows you to allocate memory basically as you normally would, without explicitly deallocating memory that is no longer useful. The collector automatically recycles memory when it determines that it can no longer be otherwise accessed.
The collector is also used by a number of programming language implementations that either use C as intermediate code, want to facilitate easier interoperation with C libraries, or just prefer the simple collector interface.
Alternatively, the garbage collector may be used as a leak detector for C or C++ programs, though that is not its primary goal.
Empirically, this collector works with most unmodified C programs, simply by replacing malloc with GC_malloc calls, replacing realloc with GC_realloc calls, and removing free calls.