1 files changed, 95 insertions, 0 deletions
diff --git a/compilerplugins/clang/externvar.cxx b/compilerplugins/clang/externvar.cxx
new file mode 100644
index 000000000..05e9820d4
--- /dev/null
+++ b/compilerplugins/clang/externvar.cxx
@@ -0,0 +1,95 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * 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/.
+ */
+
+#ifndef LO_CLANG_SHARED_PLUGINS
+
+#include "check.hxx"
+#include "plugin.hxx"
+
+// Find variable declarations at namespace scope that need not have external
+// linkage.
+
+namespace {
+
+class ExternVar: public loplugin::FilteringPlugin<ExternVar>
+{
+public:
+    explicit ExternVar(loplugin::InstantiationData const & data): FilteringPlugin(data)
+    {}
+
+    void run() override
+    { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
+
+    bool VisitVarDecl(VarDecl const * decl) {
+        if (ignoreLocation(decl)) {
+            return true;
+        }
+        if (decl->isStaticDataMember()) {
+            return true;
+        }
+        if (!(decl->isFirstDecl()
+              && compiler.getSourceManager().isInMainFile(decl->getLocation())
+              && loplugin::hasExternalLinkage(decl)))
+        {
+            return true;
+        }
+        auto def = decl->getDefinition();
+        if (def == nullptr) {
+            // Code like
+            //
+            //   namespace { extern int v; }
+            //   int f() { return sizeof(v); }
+            //
+            // is already handled by Clang itself with an error "variable 'v' is
+            // not needed and will not be emitted"
+            return true;
+        }
+        if (loplugin::DeclCheck(def).Var("_pRawDllMain").GlobalNamespace()) {
+            return true;
+        }
+        SourceLocation argLoc;
+        if (compiler.getSourceManager().isMacroArgExpansion(def->getLocation(), &argLoc)
+            && (Lexer::getImmediateMacroName(
+                    argLoc, compiler.getSourceManager(), compiler.getLangOpts())
+                == "DEFINE_GUID"))
+        {
+            return true;
+        }
+        report(
+            DiagnosticsEngine::Warning,
+            "variable with external linkage not declared in an include file",
+            def->getLocation())
+            << def->getSourceRange();
+        report(
+            DiagnosticsEngine::Note,
+            ("should either have internal linkage or be declared in an include"
+             " file"),
+            def->getLocation())
+            << def->getSourceRange();
+        for (auto prev = def;;) {
+            prev = prev->getPreviousDecl();
+            if (prev == nullptr) {
+                break;
+            }
+            report(
+                DiagnosticsEngine::Note, "previously declared here",
+                prev->getLocation())
+                << prev->getSourceRange();
+        }
+        return true;
+    }
+};
+
+loplugin::Plugin::Registration<ExternVar> externvar("externvar");
+
+}
+
+#endif // LO_CLANG_SHARED_PLUGINS
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */