[clang] [clang][StaticAnalyzer] Adding getentropy to CStringChecker. (PR #83675)

[Balazs Benics via cfe-commits]

================
@@ -2516,6 +2518,47 @@ void CStringChecker::evalSprintfCommon(CheckerContext &C, const CallEvent &Call,
   C.addTransition(State);
 }
 
+void CStringChecker::evalGetentropy(CheckerContext &C,
+                                    const CallEvent &Call) const {
+  DestinationArgExpr Buffer = {{Call.getArgExpr(0), 0}};
+  SizeArgExpr Size = {{Call.getArgExpr(1), 1}};
+  ProgramStateRef State = C.getState();
+  constexpr int BufferMaxSize = 256;
+
+  SVal SizeVal = C.getSVal(Size.Expression);
+  QualType SizeTy = Size.Expression->getType();
+
+  ProgramStateRef StateZeroSize, StateNonZeroSize;
+  std::tie(StateZeroSize, StateNonZeroSize) =
+      assumeZero(C, State, SizeVal, SizeTy);
+
+  SVal Buff = C.getSVal(Buffer.Expression);
+  State = checkNonNull(C, StateNonZeroSize, Buffer, Buff);
----------------
steakhal wrote:

`StateNonZeroSize` might be null here; see my previous comment.

https://github.com/llvm/llvm-project/pull/83675