[clang] [-Wunsafe-buffer-usage] Add fixits for array to pointer assignment (PR #81343)

[Artem Dergachev via cfe-commits]

================
@@ -848,6 +852,60 @@ class PointerAssignmentGadget : public FixableGadget {
   }
 };
 
+/// An assignment expression of the form:
+///  \code
+///  ptr = array;
+///  \endcode
+/// where `p` is a pointer and `array` is a constant size array.
+class CArrayToPtrAssignmentGadget : public FixableGadget {
+private:
+  static constexpr const char *const PointerAssignLHSTag = "ptrLHS";
+  static constexpr const char *const PointerAssignRHSTag = "ptrRHS";
+  const DeclRefExpr *PtrLHS; // the LHS pointer expression in `PA`
+  const DeclRefExpr *PtrRHS; // the RHS pointer expression in `PA`
+
+public:
+  CArrayToPtrAssignmentGadget(const MatchFinder::MatchResult &Result)
+      : FixableGadget(Kind::CArrayToPtrAssignment),
+        PtrLHS(Result.Nodes.getNodeAs<DeclRefExpr>(PointerAssignLHSTag)),
+        PtrRHS(Result.Nodes.getNodeAs<DeclRefExpr>(PointerAssignRHSTag)) {}
+
+  static bool classof(const Gadget *G) {
+    return G->getKind() == Kind::CArrayToPtrAssignment;
+  }
+
+  static Matcher matcher() {
+    auto PtrAssignExpr = binaryOperator(
+        allOf(hasOperatorName("="),
+              hasRHS(ignoringParenImpCasts(
+                  declRefExpr(hasType(hasCanonicalType(constantArrayType())),
+                              toSupportedVariable())
+                      .bind(PointerAssignRHSTag))),
+              hasLHS(declRefExpr(hasPointerType(), toSupportedVariable())
+                         .bind(PointerAssignLHSTag))));
+
+    return stmt(isInUnspecifiedUntypedContext(PtrAssignExpr));
+  }
+
+  virtual std::optional<FixItList>
+  getFixits(const FixitStrategy &S) const override;
+
+  virtual const Stmt *getBaseStmt() const override {
+    // FIXME: This should be the binary operator, assuming that this method
+    // makes sense at all on a FixableGadget.
+    return PtrLHS;
+  }
+
+  virtual DeclUseList getClaimedVarUseSites() const override {
+    return DeclUseList{PtrLHS, PtrRHS};
+  }
+
+  virtual std::optional<std::pair<const VarDecl *, const VarDecl *>>
+  getStrategyImplications() const override {
+    return {};
+  }
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haoNoQ wrote:

This is probably the default behavior 🤔

https://github.com/llvm/llvm-project/pull/81343