From a8bdb50a29062ee70c8667e4fd94dde47917f8fa Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Fri, 19 May 2023 12:19:00 -0700
Subject: [PATCH] Add useful error when symbol resolution fails

Currently if symbol resolution fails, we get:
```js
TypeError: Cannot read properties of undefined (reading 'apply')
```
It is very hard for newcomers to Emscripten to recognize this as a
symbol resolution error. Even for people experienced with this message,
it has the annoyance that it doesn't give any hint as to which symbol
went missing.

This adds a descriptive error message with the name of the missing
symbol.
---
 src/library_dylink.js | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/library_dylink.js b/src/library_dylink.js
index 7685f113c..4cfe137b2 100644
--- a/src/library_dylink.js
+++ b/src/library_dylink.js
@@ -709,6 +709,9 @@ var LibraryDylink = {
             var resolved;
             stubs[prop] = function() {
               resolved ||= resolveSymbol(prop);
+              if (!resolved) {
+                throw new Error(`Dynamic linking error: cannot resolve symbol ${prop}`);
+              }
               return resolved.apply(null, arguments);
             };
           }
-- 
2.25.1