src: introduce USE() for silencing compiler warnings

PR-URL: https://github.com/nodejs/node/pull/17333
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

3 files changed, 16 insertions, 17 deletions

diff --git a/src/async_wrap.cc b/src/async_wrap.cc
index 80543ecc66..3f77169321 100644
--- a/src/async_wrap.cc
+++ b/src/async_wrap.cc
@@ -169,8 +169,7 @@ void AsyncWrap::EmitPromiseResolve(Environment* env, double async_id) {
   Local<Value> async_id_value = Number::New(env->isolate(), async_id);
   Local<Function> fn = env->async_hooks_promise_resolve_function();
   FatalTryCatch try_catch(env);
-  fn->Call(env->context(), Undefined(env->isolate()), 1, &async_id_value)
-      .FromMaybe(Local<Value>());
+  USE(fn->Call(env->context(), Undefined(env->isolate()), 1, &async_id_value));
 }
 
 
@@ -198,8 +197,7 @@ void AsyncWrap::EmitBefore(Environment* env, double async_id) {
   Local<Value> async_id_value = Number::New(env->isolate(), async_id);
   Local<Function> fn = env->async_hooks_before_function();
   FatalTryCatch try_catch(env);
-  fn->Call(env->context(), Undefined(env->isolate()), 1, &async_id_value)
-      .FromMaybe(Local<Value>());
+  USE(fn->Call(env->context(), Undefined(env->isolate()), 1, &async_id_value));
 }
 
 
@@ -229,8 +227,7 @@ void AsyncWrap::EmitAfter(Environment* env, double async_id) {
   Local<Value> async_id_value = Number::New(env->isolate(), async_id);
   Local<Function> fn = env->async_hooks_after_function();
   FatalTryCatch try_catch(env);
-  fn->Call(env->context(), Undefined(env->isolate()), 1, &async_id_value)
-      .FromMaybe(Local<Value>());
+  USE(fn->Call(env->context(), Undefined(env->isolate()), 1, &async_id_value));
 }
 
 class PromiseWrap : public AsyncWrap {
@@ -731,8 +728,7 @@ void AsyncWrap::EmitAsyncInit(Environment* env,
   };
 
   FatalTryCatch try_catch(env);
-  init_fn->Call(env->context(), object, arraysize(argv), argv)
-      .FromMaybe(Local<Value>());
+  USE(init_fn->Call(env->context(), object, arraysize(argv), argv));
 }
 
 
diff --git a/src/node_crypto.cc b/src/node_crypto.cc
index 1b3e5004f7..23dd4a21b8 100644
--- a/src/node_crypto.cc
+++ b/src/node_crypto.cc
@@ -1820,7 +1820,7 @@ static Local<Object> X509ToObject(Environment* env, X509* cert) {
               String::NewFromUtf8(env->isolate(), mem->data,
                                   String::kNormalString, mem->length));
   }
-  (void) BIO_reset(bio);
+  USE(BIO_reset(bio));
 
   X509_NAME* issuer_name = X509_get_issuer_name(cert);
   if (X509_NAME_print_ex(bio, issuer_name, 0, X509_NAME_FLAGS) > 0) {
@@ -1829,7 +1829,7 @@ static Local<Object> X509ToObject(Environment* env, X509* cert) {
               String::NewFromUtf8(env->isolate(), mem->data,
                                   String::kNormalString, mem->length));
   }
-  (void) BIO_reset(bio);
+  USE(BIO_reset(bio));
 
   int nids[] = { NID_subject_alt_name, NID_info_access };
   Local<String> keys[] = { env->subjectaltname_string(),
@@ -1856,7 +1856,7 @@ static Local<Object> X509ToObject(Environment* env, X509* cert) {
               String::NewFromUtf8(env->isolate(), mem->data,
                                   String::kNormalString, mem->length));
 
-    (void) BIO_reset(bio);
+    USE(BIO_reset(bio));
   }
 
   EVP_PKEY* pkey = X509_get_pubkey(cert);
@@ -1873,7 +1873,7 @@ static Local<Object> X509ToObject(Environment* env, X509* cert) {
     info->Set(env->modulus_string(),
               String::NewFromUtf8(env->isolate(), mem->data,
                                   String::kNormalString, mem->length));
-    (void) BIO_reset(bio);
+    USE(BIO_reset(bio));
 
     uint64_t exponent_word = static_cast<uint64_t>(BN_get_word(e));
     uint32_t lo = static_cast<uint32_t>(exponent_word);
@@ -1887,7 +1887,7 @@ static Local<Object> X509ToObject(Environment* env, X509* cert) {
     info->Set(env->exponent_string(),
               String::NewFromUtf8(env->isolate(), mem->data,
                                   String::kNormalString, mem->length));
-    (void) BIO_reset(bio);
+    USE(BIO_reset(bio));
   }
 
   if (pkey != nullptr) {
@@ -1904,7 +1904,7 @@ static Local<Object> X509ToObject(Environment* env, X509* cert) {
   info->Set(env->valid_from_string(),
             String::NewFromUtf8(env->isolate(), mem->data,
                                 String::kNormalString, mem->length));
-  (void) BIO_reset(bio);
+  USE(BIO_reset(bio));
 
   ASN1_TIME_print(bio, X509_get_notAfter(cert));
   BIO_get_mem_ptr(bio, &mem);
@@ -2882,7 +2882,7 @@ int Connection::HandleBIOError(BIO *bio, const char* func, int rv) {
     return rv;
 
   int retry = BIO_should_retry(bio);
-  (void) retry;  // unused if !defined(SSL_PRINT_DEBUG)
+  USE(retry);  // unused if !defined(SSL_PRINT_DEBUG)
 
   if (BIO_should_write(bio)) {
     DEBUG_PRINT("[%p] BIO: %s want write. should retry %d\n",
@@ -5358,7 +5358,7 @@ void ECDH::SetPrivateKey(const FunctionCallbackInfo<Value>& args) {
   EC_KEY_set_public_key(ecdh->key_, nullptr);
 
   MarkPopErrorOnReturn mark_pop_error_on_return;
-  (void) &mark_pop_error_on_return;  // Silence compiler warning.
+  USE(&mark_pop_error_on_return);
 
   const BIGNUM* priv_key = EC_KEY_get0_private_key(ecdh->key_);
   CHECK_NE(priv_key, nullptr);
@@ -5421,7 +5421,7 @@ bool ECDH::IsKeyValidForCurve(const BIGNUM* private_key) {
 
 bool ECDH::IsKeyPairValid() {
   MarkPopErrorOnReturn mark_pop_error_on_return;
-  (void) &mark_pop_error_on_return;  // Silence compiler warning.
+  USE(&mark_pop_error_on_return);
   return 1 == EC_KEY_check_key(key_);
 }
 
diff --git a/src/util.h b/src/util.h
index 08308d837f..eb060a57b8 100644
--- a/src/util.h
+++ b/src/util.h
@@ -428,6 +428,9 @@ class BufferValue : public MaybeStackBuffer<char> {
   if (name##_length > 0)                                                      \
     CHECK_NE(name##_data, nullptr);
 
+// Use this when a variable or parameter is unused in order to explicitly
+// silence a compiler warning about that.
+template <typename T> inline void USE(T&&) {}
 
 }  // namespace node