Replace macros with C++17 features (see issue #3362)

- Convert ALLOW_UNUSED_LOCAL to [[maybe_unused]]
- Convert WARN_UNUSED_RESULT to [[nodiscard]]

include/base/cef_callback_helpers.h

@@ -52,7 +52,6 @@
 
 #include "include/base/cef_bind.h"
 #include "include/base/cef_callback.h"
-#include "include/base/cef_compiler_specific.h"
 #include "include/base/cef_logging.h"
 
 namespace base {
@@ -184,7 +183,7 @@ class ScopedClosureRunner {
   void ReplaceClosure(OnceClosure closure);
 
   // Releases the Closure without calling.
-  OnceClosure Release() WARN_UNUSED_RESULT;
+  [[nodiscard]] OnceClosure Release();
 
  private:
   OnceClosure closure_;

include/base/cef_callback_list.h

@@ -98,7 +98,6 @@
 #include "include/base/cef_bind.h"
 #include "include/base/cef_callback.h"
 #include "include/base/cef_callback_helpers.h"
-#include "include/base/cef_compiler_specific.h"
 #include "include/base/cef_logging.h"
 #include "include/base/cef_weak_ptr.h"
 
@@ -191,7 +190,7 @@ class CallbackListBase {
 
   // Registers |cb| for future notifications. Returns a CallbackListSubscription
   // whose destruction will cancel |cb|.
-  CallbackListSubscription Add(CallbackType cb) WARN_UNUSED_RESULT {
+  [[nodiscard]] CallbackListSubscription Add(CallbackType cb) {
     DCHECK(!cb.is_null());
     return CallbackListSubscription(base::BindOnce(
         &CallbackListBase::CancelCallback, weak_ptr_factory_.GetWeakPtr(),

include/base/cef_compiler_specific.h

@@ -386,26 +386,4 @@ inline constexpr bool AnalyzerAssumeTrue(bool arg) {
 #endif
 
 #endif  // !USING_CHROMIUM_INCLUDES
-
-// Annotate a function indicating the caller must examine the return value.
-// Use like:
-//   int foo() WARN_UNUSED_RESULT;
-// To explicitly ignore a result, use std::ignore from <tuple>.
-// Alternately use `[[nodiscard]]` with code that supports C++17.
-#undef WARN_UNUSED_RESULT
-#if defined(COMPILER_GCC) || defined(__clang__)
-#define WARN_UNUSED_RESULT __attribute__((warn_unused_result))
-#else
-#define WARN_UNUSED_RESULT
-#endif
-
-// Annotate a variable indicating it's ok if the variable is not used.
-// (Typically used to silence a compiler warning when the assignment
-// is important for some other reason.)
-// Use like:
-//   int x = ...;
-//   ALLOW_UNUSED_LOCAL(x);
-// Alternately use `[[maybe_unused]]` with code that supports C++17.
-#define ALLOW_UNUSED_LOCAL(x) (void)x
-
 #endif  // CEF_INCLUDE_BASE_CEF_COMPILER_SPECIFIC_H_

include/base/cef_scoped_refptr.h

@@ -46,7 +46,6 @@
 #include <type_traits>
 #include <utility>
 
-#include "include/base/cef_compiler_specific.h"
 #include "include/base/cef_logging.h"
 
 template <class T>
@@ -289,7 +288,7 @@ class TRIVIAL_ABI scoped_refptr {
 
   // Returns the owned pointer (if any), releasing ownership to the caller. The
   // caller is responsible for managing the lifetime of the reference.
-  T* release() WARN_UNUSED_RESULT;
+  [[nodiscard]] T* release();
 
   void swap(scoped_refptr& r) noexcept { std::swap(ptr_, r.ptr_); }
 

include/base/cef_scoped_typeref_mac.h

@@ -74,16 +74,15 @@
 // If the Chromium implementation diverges the below implementation should be
 // updated to match.
 
-#include "include/base/cef_compiler_specific.h"
 #include "include/base/cef_logging.h"
 #include "include/base/internal/cef_scoped_policy.h"
 
 namespace base {
 
-template<typename T>
+template <typename T>
 struct ScopedTypeRefTraits;
 
-template<typename T, typename Traits = ScopedTypeRefTraits<T>>
+template <typename T, typename Traits = ScopedTypeRefTraits<T>>
 class ScopedTypeRef {
  public:
   using element_type = T;
@@ -96,8 +95,7 @@ class ScopedTypeRef {
       object_ = Traits::Retain(object_);
   }
 
-  ScopedTypeRef(const ScopedTypeRef<T, Traits>& that)
-      : object_(that.object_) {
+  ScopedTypeRef(const ScopedTypeRef<T, Traits>& that) : object_(that.object_) {
     if (object_)
       object_ = Traits::Retain(object_);
   }
@@ -127,7 +125,7 @@ class ScopedTypeRef {
   // This is to be used only to take ownership of objects that are created
   // by pass-by-pointer create functions. To enforce this, require that the
   // object be reset to NULL before this may be used.
-  element_type* InitializeInto() WARN_UNUSED_RESULT {
+  [[nodiscard]] element_type* InitializeInto() {
     DCHECK(!object_);
     return &object_;
   }
@@ -163,7 +161,7 @@ class ScopedTypeRef {
   // ScopedTypeRef<>::release() is like std::unique_ptr<>::release.  It is NOT
   // a wrapper for Release().  To force a ScopedTypeRef<> object to call
   // Release(), use ScopedTypeRef<>::reset().
-  element_type release() WARN_UNUSED_RESULT {
+  [[nodiscard]] element_type release() {
     element_type temp = object_;
     object_ = Traits::InvalidValue();
     return temp;