util: implement util.getSystemErrorName()

Reimplement uv.errname() as internal/util.getSystemErrorName() to avoid the memory leaks caused by unknown error codes and avoid calling into C++ for the error names. Also expose it as a public API for external use. Backport-PR-URL: #18916 PR-URL: #18186 Refs: http://docs.libuv.org/en/v1.x/errors.html#c.uv_err_name Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
nodejs · Feb 26, 2018 · 28fa906 · 28fa906
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diff --git a/doc/api/util.md b/doc/api/util.md
@@ -224,6 +224,25 @@ without any formatting.
 util.format('%% %s'); // '%% %s'
 ```
 
+## util.getSystemErrorName(err)
+<!-- YAML
+added: REPLACEME
+-->
+
+* `err` {number}
+* Returns: {string}
+
+Returns the string name for a numeric error code that comes from a Node.js API.
+The mapping between error codes and error names is platform-dependent.
+See [Common System Errors][] for the names of common errors.
+
+```js
+fs.access('file/that/does/not/exist', (err) => {
+  const name = util.getSystemErrorName(err.errno);
+  console.error(name);  // ENOENT
+});
+```
+
 ## util.inherits(constructor, superConstructor)
 <!-- YAML
 added: v0.3.0
@@ -1222,5 +1241,6 @@ Deprecated predecessor of `console.log`.
 [Customizing `util.inspect` colors]: #util_customizing_util_inspect_colors
 [Internationalization]: intl.html
 [WHATWG Encoding Standard]: https://encoding.spec.whatwg.org/
-[constructor]: https://developer.mozilla.org/en-US/JavaScript/Reference/Global_Objects/Object/constructor
+[Common System Errors]: errors.html#errors_common_system_errors
+[constructor]: https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/constructor
 [semantically incompatible]: https://github.com/nodejs/node/issues/4179
diff --git a/lib/child_process.js b/lib/child_process.js
@@ -22,14 +22,15 @@
 'use strict';
 
 const util = require('util');
-const { deprecate, convertToValidSignal } = require('internal/util');
+const {
+  deprecate, convertToValidSignal, getSystemErrorName
+} = require('internal/util');
 const { isUint8Array } = require('internal/util/types');
 const { createPromise,
         promiseResolve, promiseReject } = process.binding('util');
 const debug = util.debuglog('child_process');
 const { Buffer } = require('buffer');
 const { Pipe, constants: PipeConstants } = process.binding('pipe_wrap');
-const { errname } = process.binding('uv');
 const child_process = require('internal/child_process');
 const {
   _validateStdio,
@@ -271,7 +272,7 @@ exports.execFile = function(file /*, args, options, callback*/) {
     if (!ex) {
       ex = new Error('Command failed: ' + cmd + '\n' + stderr);
       ex.killed = child.killed || killed;
-      ex.code = code < 0 ? errname(code) : code;
+      ex.code = code < 0 ? getSystemErrorName(code) : code;
       ex.signal = signal;
     }
 

diff --git a/lib/internal/util.js b/lib/internal/util.js
@@ -3,8 +3,8 @@
 const errors = require('internal/errors');
 const binding = process.binding('util');
 const { signals } = process.binding('constants').os;
-
 const { createPromise, promiseResolve, promiseReject } = binding;
+const { errmap } = process.binding('uv');
 
 const kArrowMessagePrivateSymbolIndex = binding.arrow_message_private_symbol;
 const kDecoratedPrivateSymbolIndex = binding.decorated_private_symbol;
@@ -207,6 +207,16 @@ function getConstructorOf(obj) {
   return null;
 }
 
+function getSystemErrorName(err) {
+  if (typeof err !== 'number' || err >= 0 || !Number.isSafeInteger(err)) {
+    throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'err',
+                               'negative number');
+  }
+
+  const entry = errmap.get(err);
+  return entry ? entry[0] : `Unknown system error ${err}`;
+}
+
 const kCustomPromisifiedSymbol = Symbol('util.promisify.custom');
 const kCustomPromisifyArgsSymbol = Symbol('customPromisifyArgs');
 
@@ -297,6 +307,7 @@ module.exports = {
   emitExperimentalWarning,
   filterDuplicateStrings,
   getConstructorOf,
+  getSystemErrorName,
   isError,
   join,
   normalizeEncoding,

diff --git a/lib/util.js b/lib/util.js
@@ -25,8 +25,6 @@ const errors = require('internal/errors');
 const { TextDecoder, TextEncoder } = require('internal/encoding');
 const { isBuffer } = require('buffer').Buffer;
 
-const { errname } = process.binding('uv');
-
 const {
   getPromiseDetails,
   getProxyDetails,
@@ -56,6 +54,7 @@ const {
   customInspectSymbol,
   deprecate,
   getConstructorOf,
+  getSystemErrorName,
   isError,
   promisify,
   join,
@@ -992,11 +991,7 @@ function error(...args) {
 }
 
 function _errnoException(err, syscall, original) {
-  if (typeof err !== 'number' || err >= 0 || !Number.isSafeInteger(err)) {
-    throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'err',
-                               'negative number');
-  }
-  const name = errname(err);
+  const name = getSystemErrorName(err);
   var message = `${syscall} ${name}`;
   if (original)
     message += ` ${original}`;
@@ -1085,6 +1080,7 @@ module.exports = exports = {
   debuglog,
   deprecate,
   format,
+  getSystemErrorName,
   inherits,
   inspect,
   isArray: Array.isArray,

diff --git a/src/uv.cc b/src/uv.cc
@@ -39,6 +39,8 @@ using v8::String;
 using v8::Value;
 
 
+// TODO(joyeecheung): deprecate this function in favor of
+// lib/util.getSystemErrorName()
 void ErrName(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
   int err = args[0]->Int32Value();

diff --git a/test/parallel/test-child-process-execfile.js b/test/parallel/test-child-process-execfile.js
@@ -1,8 +1,9 @@
 'use strict';
+
 const common = require('../common');
 const assert = require('assert');
 const execFile = require('child_process').execFile;
-const uv = process.binding('uv');
+const { getSystemErrorName } = require('util');
 const fixtures = require('../common/fixtures');
 
 const fixture = fixtures.path('exit.js');
@@ -27,7 +28,7 @@ const execOpts = { encoding: 'utf8', shell: true };
   const code = -1;
   const callback = common.mustCall((err, stdout, stderr) => {
     assert.strictEqual(err.toString().trim(), errorString);
-    assert.strictEqual(err.code, uv.errname(code));
+    assert.strictEqual(err.code, getSystemErrorName(code));
     assert.strictEqual(err.killed, true);
     assert.strictEqual(err.signal, null);
     assert.strictEqual(err.cmd, process.execPath);

diff --git a/test/parallel/test-net-server-listen-handle.js b/test/parallel/test-net-server-listen-handle.js
@@ -4,7 +4,7 @@ const common = require('../common');
 const assert = require('assert');
 const net = require('net');
 const fs = require('fs');
-const uv = process.binding('uv');
+const { getSystemErrorName } = require('util');
 const { TCP, constants: TCPConstants } = process.binding('tcp_wrap');
 const { Pipe, constants: PipeConstants } = process.binding('pipe_wrap');
 
@@ -47,9 +47,10 @@ function randomHandle(type) {
     handleName = `pipe ${path}`;
   }
 
-  if (errno < 0) {  // uv.errname requires err < 0
-    assert(errno >= 0, `unable to bind ${handleName}: ${uv.errname(errno)}`);
+  if (errno < 0) {
+    assert.fail(`unable to bind ${handleName}: ${getSystemErrorName(errno)}`);
   }
+
   if (!common.isWindows) {  // fd doesn't work on windows
     // err >= 0 but fd = -1, should not happen
     assert.notStrictEqual(handle.fd, -1,

diff --git a/test/parallel/test-uv-errno.js b/test/parallel/test-uv-errno.js
@@ -2,27 +2,31 @@
 
 const common = require('../common');
 const assert = require('assert');
-const util = require('util');
-const uv = process.binding('uv');
+const {
+  getSystemErrorName,
+  _errnoException
+} = require('util');
 
+const uv = process.binding('uv');
 const keys = Object.keys(uv);
 
 keys.forEach((key) => {
   if (!key.startsWith('UV_'))
     return;
 
   assert.doesNotThrow(() => {
-    const err = util._errnoException(uv[key], 'test');
+    const err = _errnoException(uv[key], 'test');
     const name = uv.errname(uv[key]);
-    assert.strictEqual(err.code, err.errno);
+    assert.strictEqual(getSystemErrorName(uv[key]), name);
     assert.strictEqual(err.code, name);
+    assert.strictEqual(err.code, err.errno);
     assert.strictEqual(err.message, `test ${name}`);
   });
 });
 
 [0, 1, 'test', {}, [], Infinity, -Infinity, NaN].forEach((key) => {
   common.expectsError(
-    () => util._errnoException(key),
+    () => _errnoException(key),
     {
       code: 'ERR_INVALID_ARG_TYPE',
       type: TypeError,

diff --git a/test/sequential/test-async-wrap-getasyncid.js b/test/sequential/test-async-wrap-getasyncid.js
@@ -7,6 +7,7 @@ const net = require('net');
 const providers = Object.assign({}, process.binding('async_wrap').Providers);
 const fixtures = require('../common/fixtures');
 const tmpdir = require('../common/tmpdir');
+const { getSystemErrorName } = require('util');
 
 // Make sure that all Providers are tested.
 {
@@ -214,7 +215,7 @@ if (common.hasCrypto) { // eslint-disable-line crypto-check
       // Use a long string to make sure the write happens asynchronously.
       const err = handle.writeLatin1String(wreq, 'hi'.repeat(100000));
       if (err)
-        throw new Error(`write failed: ${process.binding('uv').errname(err)}`);
+        throw new Error(`write failed: ${getSystemErrorName(err)}`);
       testInitialized(wreq, 'WriteWrap');
     });
     req.address = common.localhostIPv4;