create clang plugin to warn about C-style casts

We don't like C-style casts in our nice C++ code

Change-Id: I94e7ec90de9275cd6e20c4146d4f3a74bed93c9d
Reviewed-on: https://gerrit.libreoffice.org/10367
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>
Tested-by: Norbert Thiebaud <nthiebaud@gmail.com>

1 files changed, 88 insertions, 0 deletions

diff --git a/compilerplugins/clang/cstylecast.cxx b/compilerplugins/clang/cstylecast.cxx
new file mode 100644
index 000000000000..5183e26ff27e
--- /dev/null
+++ b/compilerplugins/clang/cstylecast.cxx
@@ -0,0 +1,88 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include <string>
+#include "plugin.hxx"
+#include "compat.hxx"
+
+//
+// We don't like using C-style casts in C++ code
+//
+
+namespace {
+
+class CStyleCast:
+    public RecursiveASTVisitor<CStyleCast>, public loplugin::Plugin
+{
+public:
+    explicit CStyleCast(InstantiationData const & data): Plugin(data) {}
+
+    virtual void run() override { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
+
+    bool VisitCStyleCastExpr(const CStyleCastExpr * expr);
+};
+
+static const char * recommendedFix(clang::CastKind ck) {
+    switch(ck) {
+        case CK_IntegralToPointer: return "reinterpret_cast";
+        case CK_PointerToIntegral: return "reinterpret_cast";
+        case CK_BaseToDerived: return "static_cast";
+        default: return "???";
+    }
+}
+
+bool CStyleCast::VisitCStyleCastExpr(const CStyleCastExpr * expr) {
+    if (ignoreLocation(expr)) {
+        return true;
+    }
+    // casting to void is typically used when a parameter or field is only used in
+    // debug mode, and we want to eliminate an "unused" warning
+    if( expr->getCastKind() == CK_ToVoid ) {
+        return true;
+    }
+    // ignore integral-type conversions for now, there is unsufficient agreement about
+    // the merits of C++ style casting in this case
+    if( expr->getCastKind() == CK_IntegralCast ) {
+        return true;
+    }
+    if( expr->getCastKind() == CK_NoOp ) {
+        return true;
+    }
+    // ignore pointer-type conversions for now
+    if( expr->getCastKind() == CK_BitCast ) {
+        return true;
+    }
+    SourceLocation spellingLocation = compiler.getSourceManager().getSpellingLoc(
+                              expr->getLocStart());
+    StringRef filename = compiler.getSourceManager().getFilename(spellingLocation);
+    // ignore C code
+    if ( filename.endswith(".h") || filename.endswith(".c") ) {
+        return true;
+    }
+    if ( compat::isInMainFile(compiler.getSourceManager(), spellingLocation)
+        ? (filename.startswith(SRCDIR "/sal")) // sal has tons of weird stuff going on that I don't understand enough to fix
+        : (filename.startswith(SRCDIR "/include/tools/solar.h")) ) {
+        return true;
+    }
+    report(
+        DiagnosticsEngine::Warning,
+        "c-style cast, type=%0, from=%1, recommendedFix=%2",
+        expr->getSourceRange().getBegin())
+      << expr->getCastKind()
+      << expr->getSubExprAsWritten()->getType()
+      << recommendedFix(expr->getCastKind())
+      << expr->getSourceRange();
+    return true;
+}
+
+loplugin::Plugin::Registration< CStyleCast > X("cstylecast");
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */