none*. And not cleaning up yourself also improves performance for short running apps.How so?
The libraries request memory from the kernel in pages (4k on i386, will vary on other architectures), they then run thier own heap management system within those pages. Some memory managers will return pagess to the OS when they become completely empty others will not. When the application quits the kernel cleans it up, every page it owns is reclaimed without having to even look at the memory manager structures inside.in other words freeing the memory you have allocated before quitting takes time and achives nothing usefull.