Extend loplugin:redundantcast to some suspicious reinterpret_cast

Change-Id: I5534939bfbea67d216a17891722a683c53621d36
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/140303
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

compilerplugins/clang/redundantcast.cxx

@@ -682,6 +682,24 @@ bool RedundantCast::VisitCXXReinterpretCastExpr(
             return true;
         }
     }
+    if (auto const t1 = expr->getSubExpr()->getType()->getAs<clang::PointerType>()) {
+        if (auto const t2 = expr->getType()->getAs<clang::PointerType>()) {
+            if (auto const d1 = t1->getPointeeCXXRecordDecl()) {
+                if (auto const d2 = t2->getPointeeCXXRecordDecl()) {
+                    if (d1->hasDefinition() && d1->isDerivedFrom(d2)) {
+                        report(
+                            DiagnosticsEngine::Warning,
+                            "suspicious reinterpret_cast from derived %0 to base %1, maybe this was"
+                                " meant to be a static_cast",
+                            expr->getExprLoc())
+                            << expr->getSubExprAsWritten()->getType() << expr->getTypeAsWritten()
+                            << expr->getSourceRange();
+                        return true;
+                    }
+                }
+            }
+        }
+    }
     return true;
 }
 

compilerplugins/clang/test/redundantcast.cxx

@@ -339,6 +339,13 @@ void testReinterpretConstCast() {
     (void) reinterpret_cast<std::size_t>((const_cast<int const *>(&n))); // expected-error-re {{redundant const_cast from 'int *' to 'const int *' within reinterpret_cast to fundamental type 'std::size_t' (aka 'unsigned {{.+}}') [loplugin:redundantcast]}}
 }
 
+void testSuspiciousReinterpretCast() {
+    D * p;
+    // expected-error@+1 {{suspicious reinterpret_cast from derived 'D *' to base 'S *', maybe this was meant to be a static_cast [loplugin:redundantcast]}}
+    (void) reinterpret_cast<S *>(p);
+    (void) reinterpret_cast<sal_uIntPtr>(p); // expected no error
+}
+
 void testDynamicCast() {
 
     struct S1 { virtual ~S1(); };

sw/source/core/inc/frame.hxx

@@ -195,7 +195,7 @@ public:
     public:
         FrameAreaWriteAccess(SwFrameAreaDefinition& rTarget) : SwRect(rTarget.getFrameArea()), mrTarget(rTarget) {}
         ~FrameAreaWriteAccess();
-        void setSwRect(const SwRect& rNew) { *reinterpret_cast< SwRect* >(this) = rNew; }
+        void setSwRect(const SwRect& rNew) { *static_cast< SwRect* >(this) = rNew; }
     };
 
     // same helper for FramePrintArea
@@ -210,7 +210,7 @@ public:
     public:
         FramePrintAreaWriteAccess(SwFrameAreaDefinition& rTarget) : SwRect(rTarget.getFramePrintArea()), mrTarget(rTarget) {}
         ~FramePrintAreaWriteAccess();
-        void setSwRect(const SwRect& rNew) { *reinterpret_cast< SwRect* >(this) = rNew; }
+        void setSwRect(const SwRect& rNew) { *static_cast< SwRect* >(this) = rNew; }
     };
 
     // RotateFlyFrame3 - Support for Transformations