Success with embedding ESR52 spidermonkey

In case anyone else follows my particular path (going from ESR45 to 
ESR52)  Thanks to Steve Fink and #JSAPI personage ptomato-M

The biggest problem with doing this is the source code is the only 
up-to-date documentation.  That's an ongoing Spidermonkey issue.

But the changes from JS45->JS52 are smaller than the last upgrade from 
JS38->JS45 which had some drastic and mystifying API changes that took a 
lot more support on the IRC to resolve.

Necessary changes. These might be a subset of what you'll need to do:

1. JSRuntime is no more.

2. JSClass has changed. The initialization is roughly like this below. 
Basically the array of class functions is moved out of the JSClass into 
a separate JSClassOps structure.

JSClass ScriptData::global_class = {
-    "global", JSCLASS_GLOBAL_FLAGS,
-    0,                                      // JSPropertyOp        
addProperty;
-    0,                                      // JSDeletePropertyOp  
delProperty;
-    0,                                      // JSPropertyOp        
getProperty;
-    0,                                      // JSStrictPropertyOp  
setProperty;
-    0,                                      // JSEnumerateOp       
enumerate;
-    0,                                      // JSResolveOp         resolve;
-    0,                                      // JSConvertOp         convert;
-    0,                                      // FinalizeOpType      
finalize;
-    0,                                      // JSNative            call;
-    0,                                      // JSHasInstanceOp     
hasInstance;
-    0,                                      // JSNative            
construct;
-    JS_GlobalObjectTraceHook,      // JSTraceOp           trace
-};
-
+static const JSClassOps global_ops = {
+    /* Function pointer members (may be null). */
+    nullptr,                              // JSAddPropertyOp addProperty;
+    nullptr,                              // JSDeletePropertyOp 
delProperty;
+    nullptr,                              // JSGetterOp getProperty;
+    nullptr,                              // JSSetterOp setProperty;
+    nullptr,                              // JSEnumerateOp enumerate;
+    nullptr,                              // JSResolveOp resolve;
+    nullptr,                              // JSMayResolveOp mayResolve;
+    nullptr,                              // FinalizeOp finalize;
+    nullptr,                              // JSNative call;
+    nullptr,                              // JSHasInstanceOp hasInstance;
+    nullptr,                              // JSNative construct;
+    JS_GlobalObjectTraceHook,      // JSTraceOp           trace;
+};
+/* The class of the global object. */
+JSClass ScriptData::global_class = {
+    "global",
+    JSCLASS_GLOBAL_FLAGS,
+    &global_ops
+};
+

3. JS_NewContext no longer takes the runtime argument, and the size 
argument is what the old JSRuntime init takes, e.g.
-        context = JS_NewContext(runtime, 8192);
+        context = JS_NewContext(8L * 1024L * 1024L);

4. Add JS::InitSelfHostedCode(context) after context initialization.

5. JS_SetErrorReporter is replaced by JS::SetWarningReporter.

6. JS::RootedString no longer allows JSRuntime as first argument, the 
signature with a JSContext as first argument is used instead.

7. JSWarningReporter function signature is changed:

-void ScriptData::spidercode_error(JSContext *cx, const char *message,
-            JSErrorReport* what) {
+void ScriptData::spidercode_error(JSContext *cx,JSErrorReport* what) {

And insted of the 'message' parameter, use what->message()

8. Classes with FinalizeOp member need to specify either 
JSCLASS_FOREGROUND_FINALIZE or JS_BACKGROUND_FINALIZE in the JSClass 
flags field.


9. Linking: There's an ongoing problem related to static linking, the 
ever-popular MOZ_GLUE_IN_PROGRAM bug.  There are various fixes proposed 
for that if you look in Bugzilla@Mozilla which AFAIK don't end up in any 
release yet.

I fixed it by force-loading all of the mozglue library on link:
-  -lmozglue
+  -Wl,--whole-archive -lmozglue -Wl,--no-whole-archive

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