Add an option to hicpp-signed-bitwise for positive integer literals.

This gives developers a way to deviate from the coding standard to reduce the
chattiness of the check.

clang-tools-extra/clang-tidy/hicpp/SignedBitwiseCheck.cpp

@@ -17,9 +17,24 @@ namespace clang {
 namespace tidy {
 namespace hicpp {
 
+SignedBitwiseCheck::SignedBitwiseCheck(StringRef Name,
+                                       ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      IgnorePositiveIntegerLiterals(
+          Options.get("IgnorePositiveIntegerLiterals", false)) {}
+
+void SignedBitwiseCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "IgnorePositiveIntegerLiterals",
+                IgnorePositiveIntegerLiterals);
+}
+
 void SignedBitwiseCheck::registerMatchers(MatchFinder *Finder) {
   const auto SignedIntegerOperand =
-      expr(ignoringImpCasts(hasType(isSignedInteger()))).bind("signed-operand");
+      (IgnorePositiveIntegerLiterals
+           ? expr(ignoringImpCasts(hasType(isSignedInteger())),
+                  unless(integerLiteral()))
+           : expr(ignoringImpCasts(hasType(isSignedInteger()))))
+          .bind("signed-operand");
 
   // The standard [bitmask.types] allows some integral types to be implemented
   // as signed types. Exclude these types from diagnosing for bitwise or(|) and

clang-tools-extra/clang-tidy/hicpp/SignedBitwiseCheck.h

@@ -22,10 +22,13 @@ namespace hicpp {
 /// http://clang.llvm.org/extra/clang-tidy/checks/hicpp-signed-bitwise.html
 class SignedBitwiseCheck : public ClangTidyCheck {
 public:
-  SignedBitwiseCheck(StringRef Name, ClangTidyContext *Context)
-      : ClangTidyCheck(Name, Context) {}
+  SignedBitwiseCheck(StringRef Name, ClangTidyContext *Context);
   void registerMatchers(ast_matchers::MatchFinder *Finder) override;
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+  void storeOptions(ClangTidyOptions::OptionMap &Options) override;
+
+private:
+  bool IgnorePositiveIntegerLiterals;
 };
 
 } // namespace hicpp

clang-tools-extra/docs/ReleaseNotes.rst

@@ -103,6 +103,11 @@ Improvements to clang-tidy
   Finds uses of deprecated Googletest APIs with names containing ``case`` and
   replaces them with equivalent APIs with ``suite``.
 
+- Improved :doc:`hicpp-signed-bitwise
+  <clang-tidy/checks/hicpp-signed-bitwise>` check.
+
+  The check now supports the ``IgnorePositiveIntegerLiterals`` option.
+
 - New :doc:`linuxkernel-must-use-errs
   <clang-tidy/checks/linuxkernel-must-use-errs>` check.
 

clang-tools-extra/docs/clang-tidy/checks/hicpp-signed-bitwise.rst

@@ -7,3 +7,11 @@ Finds uses of bitwise operations on signed integer types, which may lead to
 undefined or implementation defined behaviour.
 
 The according rule is defined in the `High Integrity C++ Standard, Section 5.6.1 <http://www.codingstandard.com/section/5-6-shift-operators/>`_.
+
+Options
+-------
+
+.. option:: IgnorePositiveIntegerLiterals
+
+   If this option is set to `true`, the check will not warn on bitwise operations with positive integer literals, e.g. `~0`, `2 << 1`, etc.
+   Default value is `false`.