[clang-tidy] new check cppcoreguidelines-pro-bounds-pointer-arithmetic

Summary:
This check flags all usage of pointer arithmetic, because it could lead
to an
invalid pointer.
Subtraction of two pointers is not flagged by this check.

Pointers should only refer to single objects, and pointer arithmetic is
fragile and easy to get wrong. array_view is a bounds-checked, safe type
for accessing arrays of data.

This rule is part of the "Bounds safety" profile of the C++ Core
Guidelines, see
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#-bounds1-dont-use-pointer-arithmetic-use-array_view-instead

Depends on D13313

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D13311

llvm-svn: 250116

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

@@ -2,6 +2,7 @@ set(LLVM_LINK_COMPONENTS support)
 
 add_clang_library(clangTidyCppCoreGuidelinesModule
   CppCoreGuidelinesTidyModule.cpp
+  ProBoundsPointerArithmeticCheck.cpp
   ProTypeConstCastCheck.cpp
   ProTypeReinterpretCastCheck.cpp
   ProTypeStaticCastDowncastCheck.cpp

clang-tools-extra/clang-tidy/cppcoreguidelines/CppCoreGuidelinesTidyModule.cpp

@@ -10,6 +10,7 @@
 #include "../ClangTidy.h"
 #include "../ClangTidyModule.h"
 #include "../ClangTidyModuleRegistry.h"
+#include "ProBoundsPointerArithmeticCheck.h"
 #include "ProTypeConstCastCheck.h"
 #include "ProTypeReinterpretCastCheck.h"
 #include "ProTypeStaticCastDowncastCheck.h"
@@ -22,6 +23,8 @@ namespace cppcoreguidelines {
 class CppCoreGuidelinesModule : public ClangTidyModule {
 public:
   void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
+    CheckFactories.registerCheck<ProBoundsPointerArithmeticCheck>(
+        "cppcoreguidelines-pro-bounds-pointer-arithmetic");
     CheckFactories.registerCheck<ProTypeConstCastCheck>(
         "cppcoreguidelines-pro-type-const-cast");
     CheckFactories.registerCheck<ProTypeReinterpretCastCheck>(

clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsPointerArithmeticCheck.cpp

@@ -0,0 +1,53 @@
+//===--- ProBoundsPointerArithmeticCheck.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 "ProBoundsPointerArithmeticCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+
+void ProBoundsPointerArithmeticCheck::registerMatchers(MatchFinder *Finder) {
+  if (!getLangOpts().CPlusPlus)
+    return;
+
+  // Flag all operators +, -, +=, -=, ++, -- that result in a pointer
+  Finder->addMatcher(
+      binaryOperator(anyOf(hasOperatorName("+"), hasOperatorName("-"),
+                           hasOperatorName("+="), hasOperatorName("-=")),
+                     hasType(pointerType()))
+          .bind("expr"),
+      this);
+
+  Finder->addMatcher(
+      unaryOperator(anyOf(hasOperatorName("++"), hasOperatorName("--")),
+                    hasType(pointerType()))
+          .bind("expr"),
+      this);
+
+  // Array subscript on a pointer (not an array) is also pointer arithmetic
+  Finder->addMatcher(
+      arraySubscriptExpr(hasBase(ignoringImpCasts(anyOf(hasType(pointerType()),
+                                                        hasType(decayedType(hasDecayedType(pointerType())))))))
+          .bind("expr"),
+      this);
+}
+
+void
+ProBoundsPointerArithmeticCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *MatchedExpr = Result.Nodes.getNodeAs<Expr>("expr");
+
+  diag(MatchedExpr->getExprLoc(), "do not use pointer arithmetic");
+}
+
+} // namespace tidy
+} // namespace clang

clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsPointerArithmeticCheck.h

@@ -0,0 +1,34 @@
+//===--- ProBoundsPointerArithmeticCheck.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_CPPCOREGUIDELINES_PRO_BOUNDS_POINTER_ARITHMETIC_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_PRO_BOUNDS_POINTER_ARITHMETIC_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+
+/// Flags all kinds of pointer arithmetic that have result of pointer type, i.e.
+/// +, -, +=, -=, ++, --. In addition, the [] operator on pointers (not on arrays) is flagged.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/cppcoreguidelines-pro-bounds-pointer-arithmetic.html
+class ProBoundsPointerArithmeticCheck : public ClangTidyCheck {
+public:
+  ProBoundsPointerArithmeticCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CPPCOREGUIDELINES_PRO_BOUNDS_POINTER_ARITHMETIC_H

clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines-pro-bounds-pointer-arithmetic.rst

@@ -0,0 +1,10 @@
+cppcoreguidelines-pro-bounds-pointer-arithmetic
+===============================================
+
+This check flags all usage of pointer arithmetic, because it could lead to an invalid pointer.
+Subtraction of two pointers is not flagged by this check.
+
+Pointers should only refer to single objects, and pointer arithmetic is fragile and easy to get wrong. array_view is a bounds-checked, safe type for accessing arrays of data.
+
+This rule is part of the "Bounds safety" profile of the C++ Core Guidelines, see
+https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#-bounds1-dont-use-pointer-arithmetic-use-array_view-instead

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

@@ -4,6 +4,7 @@ List of clang-tidy Checks
 .. toctree::
    cert-setlongjmp
    cert-variadic-function-def
+   cppcoreguidelines-pro-bounds-pointer-arithmetic
    cppcoreguidelines-pro-type-const-cast
    cppcoreguidelines-pro-type-reinterpret-cast
    cppcoreguidelines-pro-type-static-cast-downcast

clang-tools-extra/test/clang-tidy/cppcoreguidelines-pro-bounds-pointer-arithmetic.cpp

@@ -0,0 +1,87 @@
+// RUN: %python %S/check_clang_tidy.py %s cppcoreguidelines-pro-bounds-pointer-arithmetic %t
+
+enum E {
+  ENUM_LITERAL = 1
+};
+
+int i = 4;
+int j = 1;
+int *p = 0;
+int *q = 0;
+
+void fail() {
+  q = p + 4;
+  // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: do not use pointer arithmetic [cppcoreguidelines-pro-bounds-pointer-arithmetic]
+  p = q + i;
+  // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: do not use pointer arithmetic
+  p = q + ENUM_LITERAL;
+  // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: do not use pointer arithmetic
+
+  q = p - 1;
+  // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: do not use pointer arithmetic
+  p = q - i;
+  // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: do not use pointer arithmetic
+  p = q - ENUM_LITERAL;
+  // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: do not use pointer arithmetic
+
+  p += 4;
+  // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: do not use pointer arithmetic
+  p += i;
+  // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: do not use pointer arithmetic
+  p += ENUM_LITERAL;
+  // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: do not use pointer arithmetic
+
+  q -= 1;
+  // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: do not use pointer arithmetic
+  q -= i;
+  // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: do not use pointer arithmetic
+  q -= ENUM_LITERAL;
+  // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: do not use pointer arithmetic
+
+  p++;
+  // CHECK-MESSAGES: :[[@LINE-1]]:4: warning: do not use pointer arithmetic
+  ++p;
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: do not use pointer arithmetic
+
+  p--;
+  // CHECK-MESSAGES: :[[@LINE-1]]:4: warning: do not use pointer arithmetic
+  --p;
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: do not use pointer arithmetic
+
+  i = p[1];
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: do not use pointer arithmetic
+}
+
+struct S {
+  operator int() const;
+};
+
+void f(S &s) {
+  int *i;
+  i = i + s;
+  // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: do not use pointer arithmetic
+}
+
+void f2(int i[]) {
+  i[1] = 0;
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: do not use pointer arithmetic
+}
+
+void okay() {
+  int a[3];
+  i = a[2]; // OK, access to array
+
+  p = q;
+  p = &i;
+
+  i++;
+  ++i;
+  i--;
+  --i;
+  i += 1;
+  i -= 1;
+  i = j + 1;
+  i = j - 1;
+
+  auto diff = p - q; // OK, result is arithmetic
+}