1 files changed, 45 insertions, 5 deletions
diff --git a/ext/wasm/api/sqlite3-api-glue.c-pp.js b/ext/wasm/api/sqlite3-api-glue.c-pp.js
index 680218370..a40b83282 100644
--- a/ext/wasm/api/sqlite3-api-glue.c-pp.js
+++ b/ext/wasm/api/sqlite3-api-glue.c-pp.js
@@ -228,13 +228,49 @@ globalThis.sqlite3ApiBootstrap.initializers.push(function(sqlite3){
       }),
       '*'
     ]],
+    /**
+       We do not have a way to automatically clean up destructors
+       which are automatically converted from JS functions via the
+       final argument to sqlite3_set_auxdata(). Because of that,
+       automatic function conversion is not supported for this
+       function.  Clients should use wasm.installFunction() to create
+       such callbacks, then pass that pointer to
+       sqlite3_set_auxdata(). Relying on automated conversions here
+       would lead to leaks of JS/WASM proxy functions because
+       sqlite3_set_auxdata() is frequently called in UDFs.
+
+       The sqlite3.oo1.DB class's onclose handlers can be used for this
+       purpose. For example:
+
+       const pAuxDtor = wasm.installFunction('v(p)', function(ptr){
+         //free ptr
+       });
+       myDb.onclose = {
+         after: ()=>{
+           wasm.uninstallFunction(pAuxDtor);
+         }
+       };
+
+       Then pass pAuxDtor as the final argument to appropriate
+       sqlite3_set_auxdata() calls.
+
+       Note that versions prior to 3.49.0 ostensibly had automatic
+       function conversion here but a typo prevented it from
+       working.  Rather than fix it, it was removed because testing the
+       fix brought the huge potential for memory leaks to the
+       forefront.
+    */
     ["sqlite3_set_auxdata", undefined, [
       "sqlite3_context*", "int", "*",
-      new wasm.xWrap.FuncPtrAdapter({
-        name: 'xDestroyAuxData',
-        signature: 'v(*)',
-        contextKey: (argv, argIndex)=>argv[0/* sqlite3_context* */]
-      })
+      true
+        ? "*"
+        : new wasm.xWrap.FuncPtrAdapter({
+          /* If we can find a way to automate their cleanup, JS functions can
+             be auto-converted with this. */
+          name: 'xDestroyAuxData',
+          signature: 'v(p)',
+          contextKey: (argv, argIndex)=>argv[0/* sqlite3_context* */]
+        })
     ]],
     ["sqlite3_shutdown", undefined],
     ["sqlite3_sourceid", "string"],
@@ -1047,6 +1083,10 @@ globalThis.sqlite3ApiBootstrap.initializers.push(function(sqlite3){
       'sqlite3_set_authorizer',
       'sqlite3_trace_v2',
       'sqlite3_update_hook'
+      /*
+        We do not yet have a way to clean up automatically-converted
+        sqlite3_set_auxdata() finalizers.
+      */
     ]) {
       const x = wasm.exports[name];
       if( !x ){