From e08c008b5dea01a4f836188799e6cc6bfcbefde1 Mon Sep 17 00:00:00 2001
From: Anna Henningsen <anna@addaleax.net>
Date: Fri, 18 Oct 2019 17:05:35 +0200
Subject: [PATCH] cli: add --trace-uncaught flag

Add a flag that makes Node.js print the stack trace at the
time of *throwing* uncaught exceptions, rather than at the
creation of the `Error` object, if there is any.

This is disabled by default because it affects GC behavior.

PR-URL: https://github.com/nodejs/node/pull/30025
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
---
 doc/api/cli.md                                      | 13 +++++++++++++
 doc/node.1                                          | 12 ++++++++++++
 src/node.cc                                         |  2 ++
 src/node_errors.cc                                  | 13 +++++++++++++
 src/node_options.cc                                 |  4 ++++
 src/node_options.h                                  |  1 +
 test/message/eval_messages.out                      |  2 ++
 test/message/stdin_messages.out                     |  2 ++
 test/message/throw_error_with_getter_throw.out      |  1 +
 .../message/throw_error_with_getter_throw_traced.js | 11 +++++++++++
 .../throw_error_with_getter_throw_traced.out        | 12 ++++++++++++
 test/message/throw_null.out                         |  1 +
 test/message/throw_null_traced.js                   |  6 ++++++
 test/message/throw_null_traced.out                  | 12 ++++++++++++
 test/message/throw_undefined.out                    |  1 +
 test/message/throw_undefined_traced.js              |  6 ++++++
 test/message/throw_undefined_traced.out             | 12 ++++++++++++
 17 files changed, 111 insertions(+)
 create mode 100644 test/message/throw_error_with_getter_throw_traced.js
 create mode 100644 test/message/throw_error_with_getter_throw_traced.out
 create mode 100644 test/message/throw_null_traced.js
 create mode 100644 test/message/throw_null_traced.out
 create mode 100644 test/message/throw_undefined_traced.js
 create mode 100644 test/message/throw_undefined_traced.out

diff --git a/doc/api/cli.md b/doc/api/cli.md
index 4c7aeca7943142..e0e23c4d2c7873 100644
--- a/doc/api/cli.md
+++ b/doc/api/cli.md
@@ -775,6 +775,18 @@ added: v12.2.0
 Prints TLS packet trace information to `stderr`. This can be used to debug TLS
 connection problems.
 
+### `--trace-uncaught`
+<!-- YAML
+added: REPLACEME
+-->
+
+Print stack traces for uncaught exceptions; usually, the stack trace associated
+with the creation of an `Error` is printed, whereas this makes Node.js also
+print the stack trace associated with throwing the value (which does not need
+to be an `Error` instance).
+
+Enabling this option may affect garbage collection behavior negatively.
+
 ### `--trace-warnings`
 <!-- YAML
 added: v6.0.0
@@ -1089,6 +1101,7 @@ Node.js options that are allowed are:
 * `--trace-events-enabled`
 * `--trace-sync-io`
 * `--trace-tls`
+* `--trace-uncaught`
 * `--trace-warnings`
 * `--track-heap-objects`
 * `--unhandled-rejections`
diff --git a/doc/node.1 b/doc/node.1
index cc2726bf2fe2ad..a41c94d1a06dcc 100644
--- a/doc/node.1
+++ b/doc/node.1
@@ -346,6 +346,18 @@ Print a stack trace whenever synchronous I/O is detected after the first turn of
 .It Fl -trace-tls
 Prints TLS packet trace information to stderr.
 .
+.It Fl -trace-uncaught
+Print stack traces for uncaught exceptions; usually, the stack trace associated
+with the creation of an
+.Sy Error
+is printed, whereas this makes Node.js also
+print the stack trace associated with throwing the value (which does not need
+to be an
+.Sy Error
+instance).
+.Pp
+Enabling this option may affect garbage collection behavior negatively.
+.
 .It Fl -trace-warnings
 Print stack traces for process warnings (including deprecations).
 .
diff --git a/src/node.cc b/src/node.cc
index 8a3b1855bc35cb..2a80c46a575acf 100644
--- a/src/node.cc
+++ b/src/node.cc
@@ -232,6 +232,8 @@ int Environment::InitializeInspector(
 void Environment::InitializeDiagnostics() {
   isolate_->GetHeapProfiler()->AddBuildEmbedderGraphCallback(
       Environment::BuildEmbedderGraph, this);
+  if (options_->trace_uncaught)
+    isolate_->SetCaptureStackTraceForUncaughtExceptions(true);
 
 #if defined HAVE_DTRACE || defined HAVE_ETW
   InitDTrace(this);
diff --git a/src/node_errors.cc b/src/node_errors.cc
index 3dad079bb97f52..e094fe4681fc56 100644
--- a/src/node_errors.cc
+++ b/src/node_errors.cc
@@ -380,6 +380,19 @@ static void ReportFatalException(Environment* env,
             "%s\n%s: %s\n", *arrow_string, *name_string, *message_string);
       }
     }
+
+    if (!env->options()->trace_uncaught) {
+      PrintErrorString("(Use `node --trace-uncaught ...` to show "
+                       "where the exception was thrown)\n");
+    }
+  }
+
+  if (env->options()->trace_uncaught) {
+    Local<StackTrace> trace = message->GetStackTrace();
+    if (!trace.IsEmpty()) {
+      PrintErrorString("Thrown at:\n");
+      PrintStackTrace(env->isolate(), trace);
+    }
   }
 
   fflush(stderr);
diff --git a/src/node_options.cc b/src/node_options.cc
index c9aec4250c3ee8..9bbe08ee9e7fae 100644
--- a/src/node_options.cc
+++ b/src/node_options.cc
@@ -494,6 +494,10 @@ EnvironmentOptionsParser::EnvironmentOptionsParser() {
             "prints TLS packet trace information to stderr",
             &EnvironmentOptions::trace_tls,
             kAllowedInEnvironment);
+  AddOption("--trace-uncaught",
+            "show stack traces for the `throw` behind uncaught exceptions",
+            &EnvironmentOptions::trace_uncaught,
+            kAllowedInEnvironment);
   AddOption("--trace-warnings",
             "show stack traces on process warnings",
             &EnvironmentOptions::trace_warnings,
diff --git a/src/node_options.h b/src/node_options.h
index c2a37db73d2edf..59eddbbaa86a9c 100644
--- a/src/node_options.h
+++ b/src/node_options.h
@@ -142,6 +142,7 @@ class EnvironmentOptions : public Options {
   bool trace_deprecation = false;
   bool trace_sync_io = false;
   bool trace_tls = false;
+  bool trace_uncaught = false;
   bool trace_warnings = false;
   std::string unhandled_rejections;
   std::string userland_loader;
diff --git a/test/message/eval_messages.out b/test/message/eval_messages.out
index 0d2e68f3d79b04..8840633959a18b 100644
--- a/test/message/eval_messages.out
+++ b/test/message/eval_messages.out
@@ -55,9 +55,11 @@ ReferenceError: y is not defined
 var ______________________________________________; throw 10
                                                     ^
 10
+(Use `node --trace-uncaught ...` to show where the exception was thrown)
 
 [eval]:1
 var ______________________________________________; throw 10
                                                     ^
 10
+(Use `node --trace-uncaught ...` to show where the exception was thrown)
 done
diff --git a/test/message/stdin_messages.out b/test/message/stdin_messages.out
index dd75d0389a890e..72edb0b00b28cd 100644
--- a/test/message/stdin_messages.out
+++ b/test/message/stdin_messages.out
@@ -67,9 +67,11 @@ ReferenceError: y is not defined
 let ______________________________________________; throw 10
                                                     ^
 10
+(Use `node --trace-uncaught ...` to show where the exception was thrown)
 
 [stdin]:1
 let ______________________________________________; throw 10
                                                     ^
 10
+(Use `node --trace-uncaught ...` to show where the exception was thrown)
 done
diff --git a/test/message/throw_error_with_getter_throw.out b/test/message/throw_error_with_getter_throw.out
index 62d546d0bce862..5daf35aad44ce3 100644
--- a/test/message/throw_error_with_getter_throw.out
+++ b/test/message/throw_error_with_getter_throw.out
@@ -3,3 +3,4 @@
 throw {  // eslint-disable-line no-throw-literal
 ^
 [object Object]
+(Use `node --trace-uncaught ...` to show where the exception was thrown)
diff --git a/test/message/throw_error_with_getter_throw_traced.js b/test/message/throw_error_with_getter_throw_traced.js
new file mode 100644
index 00000000000000..609bd9caf83fe2
--- /dev/null
+++ b/test/message/throw_error_with_getter_throw_traced.js
@@ -0,0 +1,11 @@
+// Flags: --trace-uncaught
+'use strict';
+require('../common');
+throw {  // eslint-disable-line no-throw-literal
+  get stack() {
+    throw new Error('weird throw but ok');
+  },
+  get name() {
+    throw new Error('weird throw but ok');
+  },
+};
diff --git a/test/message/throw_error_with_getter_throw_traced.out b/test/message/throw_error_with_getter_throw_traced.out
new file mode 100644
index 00000000000000..5ea6aa8e269662
--- /dev/null
+++ b/test/message/throw_error_with_getter_throw_traced.out
@@ -0,0 +1,12 @@
+
+*:4
+throw {  // eslint-disable-line no-throw-literal
+^
+[object Object]
+Thrown at:
+    at *throw_error_with_getter_throw_traced.js:*:*
+    at Module._compile (internal/modules/cjs/loader.js:*:*)
+    at Module._extensions..js (internal/modules/cjs/loader.js:*:*)
+    at Module.load (internal/modules/cjs/loader.js:*:*)
+    at Module._load (internal/modules/cjs/loader.js:*:*)
+    at Module.runMain (internal/modules/cjs/loader.js:*:*)
diff --git a/test/message/throw_null.out b/test/message/throw_null.out
index c013c24d24d707..db6cc3edf583ef 100644
--- a/test/message/throw_null.out
+++ b/test/message/throw_null.out
@@ -3,3 +3,4 @@
 throw null;
 ^
 null
+(Use `node --trace-uncaught ...` to show where the exception was thrown)
diff --git a/test/message/throw_null_traced.js b/test/message/throw_null_traced.js
new file mode 100644
index 00000000000000..fee8928f887403
--- /dev/null
+++ b/test/message/throw_null_traced.js
@@ -0,0 +1,6 @@
+// Flags: --trace-uncaught
+'use strict';
+require('../common');
+
+// eslint-disable-next-line no-throw-literal
+throw null;
diff --git a/test/message/throw_null_traced.out b/test/message/throw_null_traced.out
new file mode 100644
index 00000000000000..44bc34dcbd7434
--- /dev/null
+++ b/test/message/throw_null_traced.out
@@ -0,0 +1,12 @@
+
+*test*message*throw_null_traced.js:*
+throw null;
+^
+null
+Thrown at:
+    at *throw_null_traced.js:*:*
+    at Module._compile (internal/modules/cjs/loader.js:*:*)
+    at Module._extensions..js (internal/modules/cjs/loader.js:*:*)
+    at Module.load (internal/modules/cjs/loader.js:*:*)
+    at Module._load (internal/modules/cjs/loader.js:*:*)
+    at Module.runMain (internal/modules/cjs/loader.js:*:*)
diff --git a/test/message/throw_undefined.out b/test/message/throw_undefined.out
index 5c633caa2ec69d..016eb8ffd95e33 100644
--- a/test/message/throw_undefined.out
+++ b/test/message/throw_undefined.out
@@ -3,3 +3,4 @@
 throw undefined;
 ^
 undefined
+(Use `node --trace-uncaught ...` to show where the exception was thrown)
diff --git a/test/message/throw_undefined_traced.js b/test/message/throw_undefined_traced.js
new file mode 100644
index 00000000000000..f6ded43378dc91
--- /dev/null
+++ b/test/message/throw_undefined_traced.js
@@ -0,0 +1,6 @@
+// Flags: --trace-uncaught
+'use strict';
+require('../common');
+
+// eslint-disable-next-line no-throw-literal
+throw undefined;
diff --git a/test/message/throw_undefined_traced.out b/test/message/throw_undefined_traced.out
new file mode 100644
index 00000000000000..070e9a1ec1c104
--- /dev/null
+++ b/test/message/throw_undefined_traced.out
@@ -0,0 +1,12 @@
+
+*test*message*throw_undefined_traced.js:*
+throw undefined;
+^
+undefined
+Thrown at:
+    at *throw_undefined_traced.js:*:*
+    at Module._compile (internal/modules/cjs/loader.js:*:*)
+    at Module._extensions..js (internal/modules/cjs/loader.js:*:*)
+    at Module.load (internal/modules/cjs/loader.js:*:*)
+    at Module._load (internal/modules/cjs/loader.js:*:*)
+    at Module.runMain (internal/modules/cjs/loader.js:*:*)