[clang-tidy] Add terminating continue check

Patch by: Daniel Kolozsvari!

Differential Revision: https://reviews.llvm.org/D33844

llvm-svn: 332223

clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp

@@ -40,6 +40,7 @@
 #include "SuspiciousSemicolonCheck.h"
 #include "SuspiciousStringCompareCheck.h"
 #include "SwappedArgumentsCheck.h"
+#include "TerminatingContinueCheck.h"
 #include "ThrowKeywordMissingCheck.h"
 #include "UndefinedMemoryManipulationCheck.h"
 #include "UndelegatedConstructorCheck.h"
@@ -115,6 +116,8 @@ class BugproneModule : public ClangTidyModule {
         "bugprone-suspicious-string-compare");
     CheckFactories.registerCheck<SwappedArgumentsCheck>(
         "bugprone-swapped-arguments");
+    CheckFactories.registerCheck<TerminatingContinueCheck>(
+        "bugprone-terminating-continue");
     CheckFactories.registerCheck<ThrowKeywordMissingCheck>(
         "bugprone-throw-keyword-missing");
     CheckFactories.registerCheck<UndefinedMemoryManipulationCheck>(

clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt

@@ -32,6 +32,7 @@ add_clang_library(clangTidyBugproneModule
   SuspiciousSemicolonCheck.cpp
   SuspiciousStringCompareCheck.cpp
   SwappedArgumentsCheck.cpp
+  TerminatingContinueCheck.cpp
   ThrowKeywordMissingCheck.cpp
   UndefinedMemoryManipulationCheck.cpp
   UndelegatedConstructorCheck.cpp

clang-tools-extra/clang-tidy/bugprone/TerminatingContinueCheck.cpp

@@ -0,0 +1,49 @@
+//===--- TerminatingContinueCheck.cpp - clang-tidy-------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "TerminatingContinueCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+#include "clang/Tooling/FixIt.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace bugprone {
+
+void TerminatingContinueCheck::registerMatchers(MatchFinder *Finder) {
+  const auto doWithFalse =
+      doStmt(hasCondition(ignoringImpCasts(
+                 anyOf(cxxBoolLiteral(equals(false)), integerLiteral(equals(0)),
+                       cxxNullPtrLiteralExpr(), gnuNullExpr()))),
+             equalsBoundNode("closestLoop"));
+
+  Finder->addMatcher(
+      continueStmt(hasAncestor(stmt(anyOf(forStmt(), whileStmt(),
+                                          cxxForRangeStmt(), doStmt()))
+                                   .bind("closestLoop")),
+                   hasAncestor(doWithFalse))
+          .bind("continue"),
+      this);
+}
+
+void TerminatingContinueCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *ContStmt = Result.Nodes.getNodeAs<ContinueStmt>("continue");
+
+  auto Diag =
+      diag(ContStmt->getLocStart(),
+           "'continue' in loop with false condition is equivalent to 'break'")
+      << tooling::fixit::createReplacement(*ContStmt, "break");
+}
+
+} // namespace bugprone
+} // namespace tidy
+} // namespace clang

clang-tools-extra/clang-tidy/bugprone/TerminatingContinueCheck.h

@@ -0,0 +1,36 @@
+//===--- TerminatingContinueCheck.h - clang-tidy-----------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_TERMINATINGCONTINUECHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_TERMINATINGCONTINUECHECK_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace bugprone {
+
+/// Checks if a 'continue' statement terminates the loop (i.e. the loop has
+///	a condition which always evaluates to false).
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/bugprone-terminating-continue.html
+class TerminatingContinueCheck : public ClangTidyCheck {
+public:
+  TerminatingContinueCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace bugprone
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_TERMINATINGCONTINUECHECK_H

clang-tools-extra/docs/ReleaseNotes.rst

@@ -146,6 +146,11 @@ Improvements to clang-tidy
   Warns or suggests alternatives if SIMD intrinsics are used which can be replaced by
   ``std::experimental::simd`` operations.
 
+- New :doc:`bugprone-terminating-continue
+  <clang-tidy/checks/bugprone-terminating-continue>` check
+
+  Checks if a ``continue`` statement terminates the loop.
+
 - New :doc:`zircon-temporary-objects
   <clang-tidy/checks/zircon-temporary-objects>` check.
 

clang-tools-extra/docs/clang-tidy/checks/bugprone-terminating-continue.rst

@@ -0,0 +1,17 @@
+.. title:: clang-tidy - bugprone-terminating-continue
+
+bugprone-terminating-continue
+=============================
+
+Detects `do while` loops with a condition always evaluating to false that
+have a `continue` statement, as this `continue` terminates the loop
+effectively.
+
+.. code-block:: c++
+
+  void f() {
+  do {
+  	// some code
+    continue; // terminating continue
+    // some other code
+  } while(false);

clang-tools-extra/docs/clang-tidy/checks/list.rst

@@ -49,6 +49,7 @@ Clang-Tidy Checks
    bugprone-suspicious-semicolon
    bugprone-suspicious-string-compare
    bugprone-swapped-arguments
+   bugprone-terminating-continue
    bugprone-throw-keyword-missing
    bugprone-undefined-memory-manipulation
    bugprone-undelegated-constructor

clang-tools-extra/test/clang-tidy/bugprone-terminating-continue.cpp

@@ -0,0 +1,65 @@
+// RUN: %check_clang_tidy %s bugprone-terminating-continue %t
+
+void f() {
+  do {
+    continue;
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'continue' in loop with false condition is equivalent to 'break' [bugprone-terminating-continue]
+    // CHECK-FIXES: break;
+  } while(false);
+
+  do {
+    continue;
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'continue' in loop with false condition is equivalent to 'break' [bugprone-terminating-continue]
+    // CHECK-FIXES: break;
+  } while(0);
+
+  do {
+    continue;
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'continue' in loop with false condition is equivalent to 'break' [bugprone-terminating-continue]
+    // CHECK-FIXES: break;
+  } while(nullptr);
+
+  do {
+    continue;
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'continue' in loop with false condition is equivalent to 'break' [bugprone-terminating-continue]
+    // CHECK-FIXES: break;
+  } while(__null);
+
+
+  do {
+    int x = 1;
+    if (x > 0) continue;
+    // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: 'continue' in loop with false condition is equivalent to 'break' [bugprone-terminating-continue]
+    // CHECK-FIXES: if (x > 0) break;
+  } while (false);
+}
+
+void g() {
+  do {
+    do {
+      continue;
+      int x = 1;
+    } while (1 == 1);
+  } while (false);
+
+  do {
+    for (int i = 0; i < 1; ++i) {
+      continue;
+      int x = 1;
+    }
+  } while (false);
+
+  do {
+    while (true) {
+      continue;
+      int x = 1;
+    }
+  } while (false);
+
+  int v[] = {1,2,3,34};
+  do {
+    for (int n : v) {
+      if (n>2) continue;
+    }
+  } while (false);
+}