make test_webidl robust to stack start locations

tests/webidl/output.txt

@@ -49,9 +49,10 @@ caught: a JSImplementation must implement all functions, you forgot Child2JS::vi
 |hello|43|world|41|
 12.35
 a returned string
-C string address: "string A" 0xa30
-C string address: "string B" 0xa40
-C string address: "string A" 0xa30
+C string addresses: "string A" ? "string A"  =>  0
+C string addresses: "string B" ? "string B"  =>  0
+C string addresses: "string A" ? "string B"  =>  -1
+C string addresses: "string B" ? "string A"  =>  1
 10
 object
 10

tests/webidl/post.js

@@ -104,9 +104,10 @@ suser.PrintFloat(12.3456);
 TheModule.print(suser.returnAString());
 
 // Verify that subsequent calls with the same string value re-use the string storage.
-suser.PrintCStringAddress("string A");
-suser.PrintCStringAddress("string B");
-suser.PrintCStringAddress("string A");
+suser.CompareCStringAddress("string A", "string A");
+suser.CompareCStringAddress("string B", "string B");
+suser.CompareCStringAddress("string A", "string B");
+suser.CompareCStringAddress("string B", "string A");
 
 var bv = new TheModule.RefUser(10);
 var bv2 = new TheModule.RefUser(11);

tests/webidl/test.h

@@ -60,8 +60,8 @@ public:
   void PrintFloat(float f) { printf("%.2f\n", f); }
   const char* returnAString() { return "a returned string"; }
 
-  void PrintCStringAddress(const char* s) {
-    printf("C string address: \"%s\" %p\n", s, s);
+  void CompareCStringAddress(const char* s1, const char* s2) {
+    printf("C string addresses: \"%s\" ? \"%s\"  =>  %d\n", s1, s2, s1 < s2 ? -1 : (s1 == s2 ? 0 : 1));
   }
 };
 

tests/webidl/test.idl

@@ -52,7 +52,7 @@ interface StringUser {
   void Print(long anotherInteger, DOMString anotherString);
   void PrintFloat(float f);
   [Const] DOMString returnAString();
-  void PrintCStringAddress(DOMString str);
+  void CompareCStringAddress(DOMString str1, DOMString str2);
 };
 
 interface RefUser {