[clang-tools-extra] [clang-tidy] Add `bugprone-virtual-arithmetic` check (PR #91951)

[Julian Schmidt via cfe-commits]

================
@@ -0,0 +1,59 @@
+// RUN: %check_clang_tidy %s bugprone-virtual-arithmetic %t
+
+class Base {
+public:  
+  virtual ~Base() {}
+};
+
+class Derived : public Base {};
+
+void operators() {
+  Base *b = new Derived[10];
+
+  b += 1;
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: pointer arithmetic on class 'Base' that declares a virtual function, undefined behavior if the pointee is a different class [bugprone-virtual-arithmetic]
+
+  b = b + 1;
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: pointer arithmetic on class 'Base' that declares a virtual function, undefined behavior if the pointee is a different class [bugprone-virtual-arithmetic]
+
+  b++;
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: pointer arithmetic on class 'Base' that declares a virtual function, undefined behavior if the pointee is a different class [bugprone-virtual-arithmetic]
+
+  b[1];
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: pointer arithmetic on class 'Base' that declares a virtual function, undefined behavior if the pointee is a different class [bugprone-virtual-arithmetic]
+
+  delete[] static_cast<Derived*>(b);
+}
+
+void subclassWarnings() {
+  Base *b = new Base[10];
+
+  // False positive that's impossible to distinguish without
+  // path-sensitive analysis, but the code is bug-prone regardless.
+  b += 1;
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: pointer arithmetic on class 'Base' that declares a virtual function
+
+  delete[] b;
+
+  // Common false positive is a class that overrides all parent functions.
+  Derived *d = new Derived[10];
+
+  d += 1;
+  // no-warning
+
+  delete[] d;
+}
+
+template <typename T>
+void templateWarning(T *t) {
+  // FIXME: Show the location of the template instantiation in diagnostic.
+  t += 1;
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: pointer arithmetic on class 'Base' that declares a virtual function
+}
+
+void functionArgument(Base *b) {
+  b += 1;
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: pointer arithmetic on class 'Base' that declares a virtual function
+
+  templateWarning(b);
+}
----------------
5chmidti wrote:

Please add a newline to the end of the file.

https://github.com/llvm/llvm-project/pull/91951