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-rw-r--r--compilerplugins/clang/collapseif.cxx129
1 files changed, 129 insertions, 0 deletions
diff --git a/compilerplugins/clang/collapseif.cxx b/compilerplugins/clang/collapseif.cxx
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+++ b/compilerplugins/clang/collapseif.cxx
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+/* -*- 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"
+
+/**
+ Look for nested if statements with relatively small conditions, where they can be collapsed into
+ one if statement.
+*/
+namespace
+{
+class CollapseIf : public loplugin::FilteringPlugin<CollapseIf>
+{
+public:
+ explicit CollapseIf(loplugin::InstantiationData const& data)
+ : FilteringPlugin(data)
+ {
+ }
+
+ virtual void run() override { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
+
+ bool VisitIfStmt(IfStmt const*);
+
+private:
+ int getNoCharsInSourceCodeOfExpr(IfStmt const*);
+ bool containsComment(Stmt const* stmt);
+};
+
+bool CollapseIf::VisitIfStmt(IfStmt const* ifStmt)
+{
+ if (ignoreLocation(ifStmt))
+ return true;
+ if (ifStmt->getElse())
+ return true;
+
+ IfStmt const* secondIfStmt = nullptr;
+ if (auto compoundStmt = dyn_cast<CompoundStmt>(ifStmt->getThen()))
+ {
+ if (compoundStmt->size() != 1)
+ return true;
+ secondIfStmt = dyn_cast<IfStmt>(*compoundStmt->body_begin());
+ if (!secondIfStmt)
+ return true;
+ if (secondIfStmt->getElse())
+ return true;
+ }
+ else
+ {
+ secondIfStmt = dyn_cast<IfStmt>(ifStmt->getThen());
+ if (!secondIfStmt)
+ return true;
+ }
+
+ int noChars1 = getNoCharsInSourceCodeOfExpr(ifStmt);
+ int noChars2 = getNoCharsInSourceCodeOfExpr(secondIfStmt);
+ if (noChars1 + noChars2 > 40)
+ return true;
+
+ // Sometimes there is a comment between the first and second if, so
+ // merging them would make the comment more awkward to write.
+ if (containsComment(ifStmt))
+ return true;
+
+ report(DiagnosticsEngine::Warning, "nested if should be collapsed into one statement %0 %1",
+ ifStmt->getBeginLoc())
+ << noChars1 << noChars2 << ifStmt->getSourceRange();
+ return true;
+}
+
+int CollapseIf::getNoCharsInSourceCodeOfExpr(IfStmt const* ifStmt)
+{
+ // Measure the space between the "if" the beginning of the "then" block because
+ // measuring the size of the condition expression is unreliable, because clang
+ // does not report the location of the last token accurately.
+ SourceManager& SM = compiler.getSourceManager();
+ SourceLocation startLoc = ifStmt->getBeginLoc();
+ SourceLocation endLoc = ifStmt->getThen()->getBeginLoc();
+ char const* p1 = SM.getCharacterData(startLoc);
+ char const* p2 = SM.getCharacterData(endLoc);
+
+ int count = 0;
+ for (auto p = p1; p < p2; ++p)
+ if (*p != ' ')
+ ++count;
+
+ return count;
+}
+
+bool CollapseIf::containsComment(Stmt const* stmt)
+{
+ SourceManager& SM = compiler.getSourceManager();
+ auto range = stmt->getSourceRange();
+ SourceLocation startLoc = range.getBegin();
+ SourceLocation endLoc = range.getEnd();
+ char const* p1 = SM.getCharacterData(startLoc);
+ char const* p2 = SM.getCharacterData(endLoc);
+ p2 += Lexer::MeasureTokenLength(endLoc, SM, compiler.getLangOpts());
+
+ // check for comments
+ constexpr char const comment1[] = "/*";
+ constexpr char const comment2[] = "//";
+ if (std::search(p1, p2, comment1, comment1 + strlen(comment1)) != p2)
+ return true;
+ if (std::search(p1, p2, comment2, comment2 + strlen(comment2)) != p2)
+ return true;
+
+ return false;
+}
+
+/** Off by default because some places are a judgement call if it should be collapsed or not. */
+loplugin::Plugin::Registration<CollapseIf> X("collapseif", false);
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */