[clang] [analyzer] Trust base to derived casts for dynamic types (PR #69057)

[Balazs Benics via cfe-commits]

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@@ -0,0 +1,105 @@
+// RUN: %clang_analyze_cc1 %s -verify \
+// RUN:   -analyzer-checker=core \
+// RUN:   -analyzer-checker=alpha.security.taint.TaintPropagation \
+// RUN:   -analyzer-checker=debug.ExprInspection
+
+// See issue https://github.com/llvm/llvm-project/issues/62663
+
+template <typename T> void clang_analyzer_dump(T);
+void clang_analyzer_warnIfReached();
+void clang_analyzer_numTimesReached();
+void clang_analyzer_isTainted(int);
+
+extern int scanf(const char *format, ...);
+
+class ActionHandler {
+public:
+  virtual ~ActionHandler() = default;
+  virtual void onAction(int x, int &) {
+    clang_analyzer_dump(x + 1); // expected-warning {{101}}
+  }
+};
+
+class MyHandler final : public ActionHandler {
+public:
+  void onAction(int x, int &) override {
+    clang_analyzer_dump(x + 2); // expected-warning {{202}}
+  }
+};
+
+void trust_static_types(ActionHandler *p) {
+  // This variable will help to see if conservative call evaluation happened or not.
+  int invalidation_detector;
+
+  // At this point we don't know anything about the dynamic type of `*p`, thus the `onAction` call might be resolved to the default implementation, matching the static type.
+  invalidation_detector = 1000;
+  p->onAction(100, invalidation_detector);
+  clang_analyzer_dump(invalidation_detector);
+  // expected-warning at -1 {{1000}} on this path we trusted the type, and resolved the call to `ActionHandler::onAction(int, int&)`
+  // expected-warning at -2 {{conj}} on this path we conservatively evaluated the previous call
+
+  clang_analyzer_numTimesReached(); // expected-warning {{2}} we only have that 2 paths here
+  // 1) inlined `ActionHandler::onAction(int, int&)`
+  // 2) conservatively eval called
+
+  // Trust that the `*p` refers to an object with `MyHandler` static type (or to some other sub-class).
+  auto *q = static_cast<MyHandler *>(p);
+  (void)q; // Discard the result of the cast. We already learned the type `p` might refer to.
+
+  invalidation_detector = 2000;
+  p->onAction(200, invalidation_detector);
+  clang_analyzer_dump(invalidation_detector);
+  // expected-warning at -1 {{2000}} on this path we trusted the type, and resolved the call to `MyHandler::onAction(int, int&)`
+  // expected-warning at -2 {{conj}} on this path we conservatively evaluated the previous call
+
+  clang_analyzer_numTimesReached(); // expected-warning {{3}} we only have 3 paths here, not 4
+  // 1) inlined 2 different callees
+  // 2) inlined only 1st
+  // 3) non were inlined
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steakhal wrote:

Looks as I intended.

https://github.com/llvm/llvm-project/pull/69057