`ReadOfUninitializedMemory`: Improve overall precision and recall

[knewbury01]

Affected rules

• RULE-11-6-2
• RULE-9-1
• A8-5-0
• EXP33-C
• EXP53-CPP

Description

this query makes use of approximations that underrepresent uninitialized variables and over represent definition locations. it is in the idea of only reporting cases where results are more certain, however a potential audit version of the query could be constructed that improves the potential case detection and catch some FPs and FNs that are currently not detected.

work has been done on this effort in this branch.

this improved query has benefits of:

• reuses more existing modelling
• models allocated objects in a way that reuses more out of the box library as well
• increases cases handled that involved subobjects (both potential field analysis and also array analysis)

the current improved query needs more effort on:

• still uses some approximations around field initialization (see below comment for one such improvement/but still heurisitic)
• determination on if array subobject cases should be included or not (see below comment as well for potential adjustment to align omission more with current version of query)

Example

one FP case within the unit test that will be improved is:

int *p1 = new int;
  *p1 = 0; // COMPLIANT[FALSE_POSITIVE] -- this is not found bc this is not an
           // lvalue access
  use(p1); // COMPLIANT[FALSE_POSITIVE] -- the pointee of p1 has been
           // initialized

these cases will no longer be found with the improved version of the query

one FN case within the unit test that will be improved is:

  S s1;
  S s2 = {1};

  auto i1 = s1.m1; // NON_COMPLIANT[FALSE_NEGATIVE] - rule currently is not
                   // field sensitive

this cases will be found with the improved version of the query

the examples given are run with the optional additions listed below in the comment

[knewbury01]

an alternative implementation of getInitializerExpr is:

  Expr getInitializerExpr() {
    result = this.getRootIdentity().(LocalVariable).getInitializer().getExpr()
    or
    result = this.getRootIdentity().(AllocatedObjectIdentity) and
    exists(this.getRootIdentity().(NewOrNewArrayExpr).getAChild())
  }

the reasoning here is that subobjects may wish to entirely rely on whether their root object was initialized or not.
the current branch version only deals with conditions where the subobject is the rootobject

another consideration is within the UninitializedSubobject implementation
if one wishes to align it with the current rule that disregards an array that isnt assigned via pointer then the following change needs to be made:
not this.getType().getUnspecifiedType() instanceof ArrayType -> not this.getRootIdentity().getType().getUnspecifiedType() instanceof ArrayType