loplugin:redundantcast: redundant static_casts

Change-Id: I4d50b77745d68a23136221ef06f327137e89fa7e

3 files changed, 147 insertions, 0 deletions

diff --git a/compilerplugins/clang/check.cxx b/compilerplugins/clang/check.cxx
index af9532620920..33be502c3e1c 100644
--- a/compilerplugins/clang/check.cxx
+++ b/compilerplugins/clang/check.cxx
@@ -67,6 +67,15 @@ TypeCheck TypeCheck::Pointer() const {
     return TypeCheck();
 }
 
+TypeCheck TypeCheck::Typedef() const {
+    if (!type_.isNull()) {
+        if (auto const t = type_->getAs<clang::TypedefType>()) {
+            return TypeCheck(t->desugar());
+        }
+    }
+    return TypeCheck();
+}
+
 TypeCheck TypeCheck::NotSubstTemplateTypeParmType() const {
     return
         (!type_.isNull()
diff --git a/compilerplugins/clang/check.hxx b/compilerplugins/clang/check.hxx
index d69acc264243..0c2c1bb3031f 100644
--- a/compilerplugins/clang/check.hxx
+++ b/compilerplugins/clang/check.hxx
@@ -48,6 +48,11 @@ public:
     template<std::size_t N> inline ContextCheck Class(char const (& id)[N])
         const;
 
+    TypeCheck Typedef() const;
+
+    template<std::size_t N> inline ContextCheck Typedef(char const (& id)[N])
+        const;
+
     TypeCheck NotSubstTemplateTypeParmType() const;
 
 private:
@@ -152,6 +157,22 @@ template<std::size_t N> ContextCheck TypeCheck::Class(char const (& id)[N])
     return ContextCheck();
 }
 
+template<std::size_t N> ContextCheck TypeCheck::Typedef(char const (& id)[N])
+    const
+{
+    if (!type_.isNull()) {
+        if (auto const t = type_->getAs<clang::TypedefType>()) {
+            auto const d = t->getDecl();
+            auto const i = d->getIdentifier();
+            assert(i != nullptr);
+            if (i->isStr(id)) {
+                return ContextCheck(d->getDeclContext());
+            }
+        }
+    }
+    return ContextCheck();
+}
+
 template<std::size_t N> ContextCheck DeclCheck::Class(char const (& id)[N])
     const
 {
diff --git a/compilerplugins/clang/redundantcast.cxx b/compilerplugins/clang/redundantcast.cxx
index 53d4b5b1d9a5..5215b39b18e5 100644
--- a/compilerplugins/clang/redundantcast.cxx
+++ b/compilerplugins/clang/redundantcast.cxx
@@ -25,10 +25,83 @@
 
 #include "clang/Sema/Sema.h"
 
+#include "check.hxx"
 #include "plugin.hxx"
 
 namespace {
 
+// Work around <http://reviews.llvm.org/D22128>:
+//
+// SfxErrorHandler::GetClassString (svtools/source/misc/ehdl.cxx):
+//
+//   ErrorResource_Impl aEr(aId, (sal_uInt16)lClassId);
+//   if(aEr)
+//   {
+//       rStr = static_cast<ResString>(aEr).GetString();
+//   }
+//
+// expr->dump():
+//  CXXStaticCastExpr 0x2b74e8e657b8 'class ResString' static_cast<class ResString> <ConstructorConversion>
+//  `-CXXBindTemporaryExpr 0x2b74e8e65798 'class ResString' (CXXTemporary 0x2b74e8e65790)
+//    `-CXXConstructExpr 0x2b74e8e65758 'class ResString' 'void (class ResString &&) noexcept(false)' elidable
+//      `-MaterializeTemporaryExpr 0x2b74e8e65740 'class ResString' xvalue
+//        `-CXXBindTemporaryExpr 0x2b74e8e65720 'class ResString' (CXXTemporary 0x2b74e8e65718)
+//          `-ImplicitCastExpr 0x2b74e8e65700 'class ResString' <UserDefinedConversion>
+//            `-CXXMemberCallExpr 0x2b74e8e656d8 'class ResString'
+//              `-MemberExpr 0x2b74e8e656a0 '<bound member function type>' .operator ResString 0x2b74e8dc1f00
+//                `-DeclRefExpr 0x2b74e8e65648 'struct ErrorResource_Impl' lvalue Var 0x2b74e8e653b0 'aEr' 'struct ErrorResource_Impl'
+// expr->getSubExprAsWritten()->dump():
+//  MaterializeTemporaryExpr 0x2b74e8e65740 'class ResString' xvalue
+//  `-CXXBindTemporaryExpr 0x2b74e8e65720 'class ResString' (CXXTemporary 0x2b74e8e65718)
+//    `-ImplicitCastExpr 0x2b74e8e65700 'class ResString' <UserDefinedConversion>
+//      `-CXXMemberCallExpr 0x2b74e8e656d8 'class ResString'
+//        `-MemberExpr 0x2b74e8e656a0 '<bound member function type>' .operator ResString 0x2b74e8dc1f00
+//          `-DeclRefExpr 0x2b74e8e65648 'struct ErrorResource_Impl' lvalue Var 0x2b74e8e653b0 'aEr' 'struct ErrorResource_Impl'
+//
+// Copies code from Clang's lib/AST/Expr.cpp:
+namespace {
+  Expr *skipImplicitTemporary(Expr *expr) {
+    // Skip through reference binding to temporary.
+    if (MaterializeTemporaryExpr *Materialize
+                                  = dyn_cast<MaterializeTemporaryExpr>(expr))
+      expr = Materialize->GetTemporaryExpr();
+
+    // Skip any temporary bindings; they're implicit.
+    if (CXXBindTemporaryExpr *Binder = dyn_cast<CXXBindTemporaryExpr>(expr))
+      expr = Binder->getSubExpr();
+
+    return expr;
+  }
+}
+Expr *getSubExprAsWritten(CastExpr *This) {
+  Expr *SubExpr = nullptr;
+  CastExpr *E = This;
+  do {
+    SubExpr = skipImplicitTemporary(E->getSubExpr());
+
+    // Conversions by constructor and conversion functions have a
+    // subexpression describing the call; strip it off.
+    if (E->getCastKind() == CK_ConstructorConversion)
+      SubExpr =
+        skipImplicitTemporary(cast<CXXConstructExpr>(SubExpr)->getArg(0));
+    else if (E->getCastKind() == CK_UserDefinedConversion) {
+      assert((isa<CXXMemberCallExpr>(SubExpr) ||
+              isa<BlockExpr>(SubExpr)) &&
+             "Unexpected SubExpr for CK_UserDefinedConversion.");
+      if (isa<CXXMemberCallExpr>(SubExpr))
+        SubExpr = cast<CXXMemberCallExpr>(SubExpr)->getImplicitObjectArgument();
+    }
+
+    // If the subexpression we're left with is an implicit cast, look
+    // through that, too.
+  } while ((E = dyn_cast<ImplicitCastExpr>(SubExpr)));
+
+  return SubExpr;
+}
+const Expr *getSubExprAsWritten(const CastExpr *This) {
+  return getSubExprAsWritten(const_cast<CastExpr *>(This));
+}
+
 bool isVoidPointer(QualType type) {
     return type->isPointerType()
         && type->getAs<clang::PointerType>()->getPointeeType()->isVoidType();
@@ -49,6 +122,8 @@ public:
 
     bool VisitImplicitCastExpr(ImplicitCastExpr const * expr);
 
+    bool VisitCXXStaticCastExpr(CXXStaticCastExpr const * expr);
+
     bool VisitCXXReinterpretCastExpr(CXXReinterpretCastExpr const * expr);
 
     bool VisitCXXConstCastExpr(CXXConstCastExpr const * expr);
@@ -205,6 +280,48 @@ bool RedundantCast::VisitImplicitCastExpr(const ImplicitCastExpr * expr) {
     return true;
 }
 
+bool RedundantCast::VisitCXXStaticCastExpr(CXXStaticCastExpr const * expr) {
+    if (ignoreLocation(expr)) {
+        return true;
+    }
+    auto t1 = getSubExprAsWritten(expr)->getType();
+    auto t2 = expr->getTypeAsWritten();
+    if (t1.getCanonicalType() != t2.getCanonicalType()
+        || t1->isArithmeticType())
+    {
+        return true;
+    }
+    // Don't warn about
+    //
+    //   *pResult = static_cast<oslModule>(RTLD_DEFAULT);
+    //
+    // in osl_getModuleHandle (sal/osl/unx/module.cxx) (where oslModule is a
+    // typedef to void *):
+    if (loplugin::TypeCheck(t2).Typedef("oslModule").GlobalNamespace()
+        && !loplugin::TypeCheck(t1).Typedef())
+    {
+        return true;
+    }
+    // Dont't warn about
+    //
+    //   curl_easy_setopt(static_cast<CURL*>(pData),
+    //                    CURLOPT_HEADERFUNCTION,
+    //                    memory_write_dummy);
+    //
+    // in delete_CURL (ucb/source/ucp/ftp/ftploaderthread.cxx) (where CURL is a
+    // typedef to void):
+    if (loplugin::TypeCheck(t2).Pointer().Typedef("CURL").GlobalNamespace()
+        && !loplugin::TypeCheck(t1).Pointer().Typedef())
+    {
+        return true;
+    }
+    report(
+        DiagnosticsEngine::Warning,
+        "redundant static_cast from %0 to %1", expr->getExprLoc())
+        << t1 << t2 << expr->getSourceRange();
+    return true;
+}
+
 bool RedundantCast::VisitCXXReinterpretCastExpr(
     CXXReinterpretCastExpr const * expr)
 {