new loplugin buriedassign

Change-Id: If6dd8033daf2103a81c3a7c3a44cf1e38d0a3744
Reviewed-on: https://gerrit.libreoffice.org/63466
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

2 files changed, 306 insertions, 0 deletions

diff --git a/compilerplugins/clang/buriedassign.cxx b/compilerplugins/clang/buriedassign.cxx
new file mode 100644
index 000000000000..8d0e6cc79e59
--- /dev/null
+++ b/compilerplugins/clang/buriedassign.cxx
@@ -0,0 +1,226 @@
+/* -*- 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 <cassert>
+#include <string>
+#include <iostream>
+#include <unordered_map>
+#include <unordered_set>
+
+#include "plugin.hxx"
+#include "check.hxx"
+#include "clang/AST/CXXInheritance.h"
+#include "clang/AST/StmtVisitor.h"
+
+/**
+  TODO deal with C++ operator overload assign
+*/
+
+namespace
+{
+//static bool startswith(const std::string& rStr, const char* pSubStr) {
+//    return rStr.compare(0, strlen(pSubStr), pSubStr) == 0;
+//}
+class BuriedAssign : public loplugin::FilteringPlugin<BuriedAssign>
+{
+public:
+    explicit BuriedAssign(loplugin::InstantiationData const& data)
+        : FilteringPlugin(data)
+    {
+    }
+
+    virtual void run() override
+    {
+        std::string fn(handler.getMainFileName());
+        loplugin::normalizeDotDotInFilePath(fn);
+        // getParentStmt appears not to be working very well here
+        if (fn == SRCDIR "/stoc/source/inspect/introspection.cxx"
+            || fn == SRCDIR "/stoc/source/corereflection/criface.cxx")
+            return;
+        // calling an acquire via function pointer
+        if (fn == SRCDIR "/cppu/source/uno/lbenv.cxx"
+            || fn == SRCDIR "cppu/source/typelib/static_types.cxx")
+            return;
+        // false+, not sure why
+        if (fn == SRCDIR "/vcl/source/window/menu.cxx")
+            return;
+        TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+    bool VisitBinaryOperator(BinaryOperator const*);
+    bool VisitCXXOperatorCallExpr(CXXOperatorCallExpr const*);
+
+private:
+    void checkExpr(Expr const*);
+};
+
+static bool isAssignmentOp(clang::BinaryOperatorKind op)
+{
+    // We ignore BO_ShrAssign i.e. >>= because we use that everywhere for
+    // extracting data from css::uno::Any
+    return op == BO_Assign || op == BO_MulAssign || op == BO_DivAssign || op == BO_RemAssign
+           || op == BO_AddAssign || op == BO_SubAssign || op == BO_ShlAssign || op == BO_AndAssign
+           || op == BO_XorAssign || op == BO_OrAssign;
+}
+
+static bool isAssignmentOp(clang::OverloadedOperatorKind Opc)
+{
+    // Same logic as CXXOperatorCallExpr::isAssignmentOp(), which our supported clang
+    // doesn't have yet.
+    // Except that we ignore OO_GreaterGreaterEqual i.e. >>= because we use that everywhere for
+    // extracting data from css::uno::Any
+    return Opc == OO_Equal || Opc == OO_StarEqual || Opc == OO_SlashEqual || Opc == OO_PercentEqual
+           || Opc == OO_PlusEqual || Opc == OO_MinusEqual || Opc == OO_LessLessEqual
+           || Opc == OO_AmpEqual || Opc == OO_CaretEqual || Opc == OO_PipeEqual;
+}
+
+bool BuriedAssign::VisitBinaryOperator(BinaryOperator const* binaryOp)
+{
+    if (ignoreLocation(binaryOp))
+        return true;
+
+    if (!isAssignmentOp(binaryOp->getOpcode()))
+        return true;
+
+    checkExpr(binaryOp);
+    return true;
+}
+
+bool BuriedAssign::VisitCXXOperatorCallExpr(CXXOperatorCallExpr const* cxxOper)
+{
+    if (ignoreLocation(cxxOper))
+        return true;
+    if (!isAssignmentOp(cxxOper->getOperator()))
+        return true;
+    checkExpr(cxxOper);
+    return true;
+}
+
+void BuriedAssign::checkExpr(Expr const* binaryOp)
+{
+    if (compiler.getSourceManager().isMacroBodyExpansion(compat::getBeginLoc(binaryOp)))
+        return;
+    if (compiler.getSourceManager().isMacroArgExpansion(compat::getBeginLoc(binaryOp)))
+        return;
+
+    /**
+    Note: I tried writing this plugin without getParentStmt, but in order to make that work, I had to
+    hack things like TraverseWhileStmt to call TraverseStmt on the child nodes myself, so I could know whether I was inside the body or the condition.
+    But I could not get that to work, so switched to this approach.
+    */
+
+    // look up past the temporary nodes
+    Stmt const* child = binaryOp;
+    Stmt const* parent = getParentStmt(binaryOp);
+    while (true)
+    {
+        // This part is not ideal, but getParentStmt() appears to fail us in some cases, notably when the assignment
+        // is inside a decl like:
+        //     int x = a = 1;
+        if (!parent)
+            return;
+        if (!(isa<MaterializeTemporaryExpr>(parent) || isa<CXXBindTemporaryExpr>(parent)
+              || isa<ImplicitCastExpr>(parent) || isa<CXXConstructExpr>(parent)
+              || isa<ParenExpr>(parent) || isa<ExprWithCleanups>(parent)))
+            break;
+        child = parent;
+        parent = getParentStmt(parent);
+    }
+
+    if (isa<CompoundStmt>(parent))
+        return;
+    // ignore chained assignment like "a = b = 1;"
+    if (auto cxxOper = dyn_cast<CXXOperatorCallExpr>(parent))
+    {
+        if (cxxOper->getOperator() == OO_Equal)
+            return;
+    }
+    // ignore chained assignment like "a = b = 1;"
+    if (auto parentBinOp = dyn_cast<BinaryOperator>(parent))
+    {
+        if (parentBinOp->getOpcode() == BO_Assign)
+            return;
+    }
+    // ignore chained assignment like "int a = b = 1;"
+    if (isa<DeclStmt>(parent))
+        return;
+
+    if (isa<CaseStmt>(parent) || isa<DefaultStmt>(parent) || isa<LabelStmt>(parent)
+        || isa<ForStmt>(parent) || isa<CXXForRangeStmt>(parent) || isa<IfStmt>(parent)
+        || isa<DoStmt>(parent) || isa<WhileStmt>(parent) || isa<ReturnStmt>(parent))
+        return;
+
+    // now check for the statements where we don't care at all if we see a buried assignment
+    while (true)
+    {
+        if (isa<CompoundStmt>(parent))
+            break;
+        if (isa<CaseStmt>(parent) || isa<DefaultStmt>(parent) || isa<LabelStmt>(parent))
+            return;
+        // Ignore assign in these statements, just seems to be part of the "natural" idiom of C/C++
+        // TODO: perhaps include ReturnStmt?
+        if (auto forStmt = dyn_cast<ForStmt>(parent))
+        {
+            if (child == forStmt->getBody())
+                break;
+            return;
+        }
+        if (auto forRangeStmt = dyn_cast<CXXForRangeStmt>(parent))
+        {
+            if (child == forRangeStmt->getBody())
+                break;
+            return;
+        }
+        if (auto ifStmt = dyn_cast<IfStmt>(parent))
+        {
+            if (child == ifStmt->getCond())
+                return;
+        }
+        if (auto doStmt = dyn_cast<DoStmt>(parent))
+        {
+            if (child == doStmt->getCond())
+                return;
+        }
+        if (auto whileStmt = dyn_cast<WhileStmt>(parent))
+        {
+            if (child == whileStmt->getBody())
+                break;
+            return;
+        }
+        if (isa<ReturnStmt>(parent))
+            return;
+        // This appears to be a valid way of making it obvious that we need to call acquire when assigning such ref-counted
+        // stuff e.g.
+        //     rtl_uString_acquire( a = b );
+        if (auto callExpr = dyn_cast<CallExpr>(parent))
+        {
+            if (callExpr->getDirectCallee() && callExpr->getDirectCallee()->getIdentifier())
+            {
+                auto name = callExpr->getDirectCallee()->getName();
+                if (name == "rtl_uString_acquire" || name == "_acquire"
+                    || name == "typelib_typedescriptionreference_acquire")
+                    return;
+            }
+        }
+        child = parent;
+        parent = getParentStmt(parent);
+        if (!parent)
+            break;
+    }
+
+    report(DiagnosticsEngine::Warning, "buried assignment, very hard to read",
+           compat::getBeginLoc(binaryOp))
+        << binaryOp->getSourceRange();
+}
+
+// off by default because it uses getParentStmt so it's more expensive to run
+loplugin::Plugin::Registration<BuriedAssign> X("buriedassign", false);
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/compilerplugins/clang/test/buriedassign.cxx b/compilerplugins/clang/test/buriedassign.cxx
new file mode 100644
index 000000000000..7e41a83ccaa5
--- /dev/null
+++ b/compilerplugins/clang/test/buriedassign.cxx
@@ -0,0 +1,80 @@
+/* -*- 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/.
+ */
+
+#include <map>
+#include <rtl/ustring.hxx>
+
+namespace test1
+{
+int foo(int);
+
+void main()
+{
+    int x = 1;
+    foo(x = 2); // expected-error {{buried assignment, very hard to read [loplugin:buriedassign]}}
+    int y = x = 1; // no warning expected
+    (void)y;
+    int z = foo(
+        x = 1); // expected-error {{buried assignment, very hard to read [loplugin:buriedassign]}}
+    (void)z;
+    switch (x = 1)
+    { // expected-error@-1 {{buried assignment, very hard to read [loplugin:buriedassign]}}
+    }
+    std::map<int, int> map1;
+    map1[x = 1]
+        = 1; // expected-error@-1 {{buried assignment, very hard to read [loplugin:buriedassign]}}
+}
+}
+
+namespace test2
+{
+struct MyInt
+{
+    int x;
+    MyInt(int i)
+        : x(i)
+    {
+    }
+    MyInt& operator=(MyInt const&) = default;
+    MyInt& operator=(int) { return *this; }
+    bool operator<(MyInt const& other) const { return x < other.x; }
+};
+
+MyInt foo(MyInt);
+
+void main()
+{
+    MyInt x = 1;
+    foo(x = 2); // expected-error {{buried assignment, very hard to read [loplugin:buriedassign]}}
+    MyInt y = x = 1; // no warning expected
+    (void)y;
+    MyInt z = foo(
+        x = 1); // expected-error {{buried assignment, very hard to read [loplugin:buriedassign]}}
+    (void)z;
+    z = x; // no warning expected
+    std::map<MyInt, int> map1;
+    map1[x = 1]
+        = 1; // expected-error@-1 {{buried assignment, very hard to read [loplugin:buriedassign]}}
+}
+}
+
+namespace test3
+{
+void main(OUString sUserAutoCorrFile, OUString sExt)
+{
+    OUString sRet;
+    if (sUserAutoCorrFile == "xxx")
+        sRet = sUserAutoCorrFile; // no warning expected
+    if (sUserAutoCorrFile == "yyy")
+        (sRet = sUserAutoCorrFile)
+            += sExt; // expected-error@-1 {{buried assignment, very hard to read [loplugin:buriedassign]}}
+}
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */