src: lazily load internalBinding('uv') and build the errmap lazily

This removes the `internalBinding('uv')` call from the normal
bootstrap for now, and avoids building `errmap` by default which
expands to a lot of calls into V8.

PR-URL: https://github.com/nodejs/node/pull/25143
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

lib/internal/errors.js

@@ -15,11 +15,6 @@ const kInfo = Symbol('info');
 const messages = new Map();
 const codes = {};
 
-const {
-  errmap,
-  UV_EAI_NODATA,
-  UV_EAI_NONAME
-} = internalBinding('uv');
 const { kMaxLength } = internalBinding('buffer');
 const { defineProperty } = Object;
 
@@ -237,6 +232,24 @@ function getMessage(key, args) {
   return util.format.apply(null, args);
 }
 
+let uvBinding;
+
+function lazyUv() {
+  if (!uvBinding) {
+    uvBinding = internalBinding('uv');
+  }
+  return uvBinding;
+}
+
+function lazyErrmapGet(name) {
+  uvBinding = lazyUv();
+  if (!uvBinding.errmap) {
+    uvBinding.errmap = uvBinding.getErrorMap();
+  }
+  return uvBinding.errmap.get(name);
+}
+
+
 /**
  * This creates an error compatible with errors produced in the C++
  * function UVException using a context object with data assembled in C++.
@@ -247,7 +260,7 @@ function getMessage(key, args) {
  * @returns {Error}
  */
 function uvException(ctx) {
-  const [ code, uvmsg ] = errmap.get(ctx.errno);
+  const [ code, uvmsg ] = lazyErrmapGet(ctx.errno);
   let message = `${code}: ${ctx.message || uvmsg}, ${ctx.syscall}`;
 
   let path;
@@ -303,7 +316,7 @@ function uvException(ctx) {
  * @returns {Error}
  */
 function uvExceptionWithHostPort(err, syscall, address, port) {
-  const [ code, uvmsg ] = errmap.get(err);
+  const [ code, uvmsg ] = lazyErrmapGet(err);
   const message = `${syscall} ${code}: ${uvmsg}`;
   let details = '';
 
@@ -421,7 +434,7 @@ function dnsException(code, syscall, hostname) {
   if (typeof code === 'number') {
     // FIXME(bnoordhuis) Remove this backwards compatibility nonsense and pass
     // the true error to the user. ENOTFOUND is not even a proper POSIX error!
-    if (code === UV_EAI_NODATA || code === UV_EAI_NONAME) {
+    if (code === lazyUv().UV_EAI_NODATA || code === lazyUv().UV_EAI_NONAME) {
       code = 'ENOTFOUND'; // Fabricated error name.
     } else {
       code = lazyInternalUtil().getSystemErrorName(code);

lib/internal/util.js

@@ -16,8 +16,6 @@ const {
   isNativeError
 } = require('internal/util/types');
 
-const { errmap } = internalBinding('uv');
-
 const noCrypto = !process.versions.openssl;
 
 const experimentalWarnings = new Set();
@@ -250,8 +248,19 @@ function getConstructorOf(obj) {
   return null;
 }
 
+let uvBinding;
+function lazyErrmapGet(name) {
+  if (!uvBinding) {
+    uvBinding = internalBinding('uv');
+  }
+  if (!uvBinding.errmap) {
+    uvBinding.errmap = uvBinding.getErrorMap();
+  }
+  return uvBinding.errmap.get(name);
+}
+
 function getSystemErrorName(err) {
-  const entry = errmap.get(err);
+  const entry = lazyErrmapGet(err);
   return entry ? entry[0] : `Unknown system error ${err}`;
 }
 

src/uv.cc

@@ -25,20 +25,39 @@
 #include "env-inl.h"
 
 namespace node {
+
+namespace per_process {
+struct UVError {
+  int value;
+  const char* name;
+  const char* message;
+};
+
+// We only expand the macro once here to reduce the amount of code
+// generated.
+static const struct UVError uv_errors_map[] = {
+#define V(name, message) {UV_##name, #name, message},
+    UV_ERRNO_MAP(V)
+#undef V
+};
+}  // namespace per_process
+
 namespace {
 
 using v8::Array;
 using v8::Context;
+using v8::DontDelete;
 using v8::FunctionCallbackInfo;
 using v8::Integer;
 using v8::Isolate;
 using v8::Local;
 using v8::Map;
 using v8::Object;
+using v8::PropertyAttribute;
+using v8::ReadOnly;
 using v8::String;
 using v8::Value;
 
-
 void ErrName(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
   if (env->options()->pending_deprecation && env->EmitErrNameWarning()) {
@@ -57,6 +76,29 @@ void ErrName(const FunctionCallbackInfo<Value>& args) {
   args.GetReturnValue().Set(OneByteString(env->isolate(), name));
 }
 
+void GetErrMap(const FunctionCallbackInfo<Value>& args) {
+  Environment* env = Environment::GetCurrent(args);
+  Isolate* isolate = env->isolate();
+  Local<Context> context = env->context();
+
+  Local<Map> err_map = Map::New(isolate);
+
+  size_t errors_len = arraysize(per_process::uv_errors_map);
+  for (size_t i = 0; i < errors_len; ++i) {
+    const auto& error = per_process::uv_errors_map[i];
+    Local<Value> arr[] = {OneByteString(isolate, error.name),
+                          OneByteString(isolate, error.message)};
+    if (err_map
+            ->Set(context,
+                  Integer::New(isolate, error.value),
+                  Array::New(isolate, arr, arraysize(arr)))
+            .IsEmpty()) {
+      return;
+    }
+  }
+
+  args.GetReturnValue().Set(err_map);
+}
 
 void Initialize(Local<Object> target,
                 Local<Value> unused,
@@ -70,28 +112,21 @@ void Initialize(Local<Object> target,
                   ->GetFunction(env->context())
                   .ToLocalChecked()).FromJust();
 
-#define V(name, _) NODE_DEFINE_CONSTANT(target, UV_##name);
-  UV_ERRNO_MAP(V)
-#undef V
+  // TODO(joyeecheung): This should be deprecated in user land in favor of
+  // `util.getSystemErrorName(err)`.
+  PropertyAttribute attributes =
+      static_cast<PropertyAttribute>(ReadOnly | DontDelete);
+  size_t errors_len = arraysize(per_process::uv_errors_map);
+  const std::string prefix = "UV_";
+  for (size_t i = 0; i < errors_len; ++i) {
+    const auto& error = per_process::uv_errors_map[i];
+    const std::string prefixed_name = prefix + error.name;
+    Local<String> name = OneByteString(isolate, prefixed_name.c_str());
+    Local<Integer> value = Integer::New(isolate, error.value);
+    target->DefineOwnProperty(context, name, value, attributes).FromJust();
+  }
 
-  Local<Map> err_map = Map::New(isolate);
-
-#define V(name, msg) do {                                                     \
-  Local<Value> arr[] = {                                                      \
-    OneByteString(isolate, #name),                                            \
-    OneByteString(isolate, msg)                                               \
-  };                                                                          \
-  if (err_map->Set(context,                                                   \
-                   Integer::New(isolate, UV_##name),                          \
-                   Array::New(isolate, arr, arraysize(arr))).IsEmpty()) {     \
-    return;                                                                   \
-  }                                                                           \
-} while (0);
-  UV_ERRNO_MAP(V)
-#undef V
-
-  target->Set(context, FIXED_ONE_BYTE_STRING(isolate, "errmap"),
-              err_map).FromJust();
+  env->SetMethod(target, "getErrorMap", GetErrMap);
 }
 
 }  // anonymous namespace