From 068d4108e5ae41ca5bc2bcf22277e6235c6bdd0b Mon Sep 17 00:00:00 2001
From: Noel <noel.grandin@collabora.co.uk>
Date: Tue, 2 Feb 2021 09:41:52 +0200
Subject: loplugin:redundantcast catch more dynamic_cast

Change-Id: Ia28e58217cefa306567b53688d851fa210b7821c
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/110287
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
---
 compilerplugins/clang/redundantcast.cxx      | 37 +++++++++++++++++++++++-----
 compilerplugins/clang/test/redundantcast.cxx |  5 +++-
 2 files changed, 35 insertions(+), 7 deletions(-)

(limited to 'compilerplugins/clang')

diff --git a/compilerplugins/clang/redundantcast.cxx b/compilerplugins/clang/redundantcast.cxx
index bdac3f3bcc56..afc1cb414681 100644
--- a/compilerplugins/clang/redundantcast.cxx
+++ b/compilerplugins/clang/redundantcast.cxx
@@ -800,16 +800,41 @@ bool RedundantCast::VisitCXXDynamicCastExpr(CXXDynamicCastExpr const * expr) {
     if (ignoreLocation(expr)) {
         return true;
     }
-    // so far this only deals with dynamic casting from T to T
     auto const sub = compat::getSubExprAsWritten(expr);
     auto const t1 = expr->getTypeAsWritten();
     auto const t2 = sub->getType();
-    if (t1.getCanonicalType() != t2.getCanonicalType())
+    QualType qt1 = t1.getCanonicalType();
+    QualType qt2 = t2.getCanonicalType();
+    if (qt1 == qt2)
+    {
+        report(
+            DiagnosticsEngine::Warning,
+            "redundant dynamic cast from %0 to %1", expr->getExprLoc())
+            << t2 << t1 << expr->getSourceRange();
         return true;
-    report(
-        DiagnosticsEngine::Warning,
-        "redundant dynamic cast from %0 to %1", expr->getExprLoc())
-        << t2 << t1 << expr->getSourceRange();
+    }
+    if (qt1->isPointerType() && qt2->isPointerType())
+    {
+        // casting from 'T*' to 'const T*' is redundant, so compare without the qualifiers
+        qt1 = qt1->getPointeeType().getUnqualifiedType();
+        qt2 = qt2->getPointeeType().getUnqualifiedType();
+        if (qt1 == qt2)
+        {
+            report(
+                DiagnosticsEngine::Warning,
+                "redundant dynamic cast from %0 to %1", expr->getExprLoc())
+                << t2 << t1 << expr->getSourceRange();
+            return true;
+        }
+        if (qt1->getAsCXXRecordDecl() && qt2->getAsCXXRecordDecl()->isDerivedFrom(qt1->getAsCXXRecordDecl()))
+        {
+            report(
+                DiagnosticsEngine::Warning,
+                "redundant dynamic upcast from %0 to %1", expr->getExprLoc())
+                << t2 << t1 << expr->getSourceRange();
+            return true;
+        }
+    }
     return true;
 }
 
diff --git a/compilerplugins/clang/test/redundantcast.cxx b/compilerplugins/clang/test/redundantcast.cxx
index 03ce47796d65..97f4e6f73777 100644
--- a/compilerplugins/clang/test/redundantcast.cxx
+++ b/compilerplugins/clang/test/redundantcast.cxx
@@ -340,11 +340,14 @@ void testDynamicCast() {
 
     S1 * s1 = nullptr;
     S2 * s2 = nullptr;
+    S3 * s3 = nullptr;
 
     (void) dynamic_cast<S2 *>(s1);
-    (void) dynamic_cast<S1 *>(s2);
+    (void) dynamic_cast<S1 *>(s2); // expected-error {{redundant dynamic upcast from 'S2 *' to 'S1 *' [loplugin:redundantcast]}}
     (void) dynamic_cast<S2 *>(s2); // expected-error {{redundant dynamic cast from 'S2 *' to 'S2 *' [loplugin:redundantcast]}}
     (void) dynamic_cast<S3 *>(s2);
+    (void) dynamic_cast<const S2 *>(s2); // expected-error {{redundant dynamic cast from 'S2 *' to 'const S2 *' [loplugin:redundantcast]}}
+    (void) dynamic_cast<S1 *>(s3); // expected-error {{redundant dynamic upcast from 'S3 *' to 'S1 *' [loplugin:redundantcast]}}
 }
 
 void overload(int);
-- 
cgit