Subj : Re: (SpiderMonkey Question) Help calling script functions from C
To   : zaphod <zaphodthefirst@hotmail.com>
From : Brendan Eich <brendan@meer.net>
Date : Thu Oct 02 2003 08:40 pm

zaphod wrote:

> > Here is the code (this snippet has been pruned down,
> in the real code I check all of the return values from
> the JS_* functions and am sure that the runtime,
> context and global object are created properly.
> 
> char * script =
> "  var save;                        \n"
> "                                   \n"
> "  function setvalue(val) {         \n"
> "    save = val;                    \n"
> "  }                                \n"
> "                                   \n"
> "  function getvalue() {            \n"
> "    return save;                   \n"
> "  }                                \n"
> ;


Aside: better form is const char script[] = "..." -- you don't want a 
non-const pointer to non-const chars, you want a (constant by 
definition) array named script of const chars.

> 
> JSClass globalclass;
> 
> void MyFillClass(JSClass * jsclass, char * name)
> {
>   memset(jsclass, 0, sizeof(*jsclass));
>   jsclass->name = name;
>   jsclass->addProperty  = JS_PropertyStub;
>   jsclass->delProperty  = JS_PropertyStub;
>   jsclass->getProperty  = JS_PropertyStub;
>   jsclass->setProperty  = JS_PropertyStub;
>   jsclass->enumerate    = JS_EnumerateStub;
>   jsclass->resolve      = JS_ResolveStub;
>   jsclass->convert      = JS_ConvertStub;
>   jsclass->finalize     = JS_FinalizeStub;
> }


Trim this further by static initialization of globalclass.  No need for 
MyFillClass.


>   JS_InitStandardClasses(context, global);
>   JS_CompileScript(context, global, script, (uintN)strlen(script), "static", 0);


Here is your problem.

Just compiling script has no effect on global (passing global when 
pre-compiling, however, does help the compiler to optimize for the case 
when you then execute script using global as its scope chain).  You must 
execute after compiling.  Use JS_EvaluateScript to compile and execute.


>   
>   {
>     char * str;
>     
>     jsval argv[2];
>     jsval retv;
>     
>     JSIdArray * arr = JS_Enumerate(context, object);
>     printf("global object has %d properties", arr->length);
>     
>     str = (char *)JS_malloc(context, strlen("Hello World !") + 1);
>     strcpy(str, "Hello World !");
>     
>     argv[0] = STRING_TO_JSVAL(JS_NewString(context, str, strlen(str)));


Use JS_NewStringCopyZ to combine the JS_malloc and JS_NewString calls 
and error checking logic.

/be

.