analyze: initial implementation of NON_NULL static analysis #1081
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fw-immunant
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This adds a very basic static analysis for
NON_NULLwithin the currentdataflowframework. It starts by optimistically assuming that all pointers areNON_NULL, and removes the permission from pointers into which aptr::null()or equivalent might flow. This branch just implements the static analysis, not rewriting.I'm actually not a huge fan of this design - I think we'd probably get much better results with a path-sensitive analysis that can handle common patterns from C like
if !p.is_null() { let q = (&p).field; /* use q... */ }by detecting null checks in the CFG. But the simple path-insensitive version is sufficient for now, and gives us somewhere to plug in the dynamic analysis results.