What's the relation between malloc diagnostics and malloc related environment variables?

Here there's a list of environment variables about the malloc package:

• MallocStackLogging
• MallocStackLoggingNoCompact
• MallocPreScribble
• MallocScribble
• MallocGuardEdges
• MallocDoNotProtectPrelude
• MallocDoNotProtectPostlude
• MallocCheckHeapStart
• MallocCheckHeapEach
• MallocCheckHeapSleep
• MallocCheckHeapAbort
• MallocBadFreeAbort

Also, when I open the Diagnostics section of my project from XCode 4, I see that under Memory Management, there are

• Enable Scribble
• Enable Guard Edges
• Enable Guard Malloc

So, I'm a little bit confused. Should these environme开发者_StackOverflow中文版nt variables be used in combination with the diagnostics settings, or are these diagnostics settings a shortcut for enabling the environment variables listed above?

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To my knowledge they're shortcuts to the most common options; to use the others you need to set with environment variables.