Subj : Re: crash in JS_NewContext
To   : Weiyang Zhou
From : Brendan Eich
Date : Wed Sep 07 2005 11:53 am

Weiyang Zhou wrote:
> Hi,
> 
> We are porting SpiderMonkey to an embedded system running on a RISC 32bit 
> microprocessor.

What compiler are you using?

>     str = ALIGN(buf, JSString);

Could you please provide disassembly of the generated code for this line?

What you describe, especially the following, sounds like a compiler bug.

/be

>     {
> 
>         char buffer[256];
> 
>         sprintf(buffer, "%x %x %d %d %d\n", buf, str, ALIGNMENT(JSString), 
> sizeof(JSString), (jsuword)(buf) % ALIGNMENT(JSString));
> 
>         printf("%s", buffer);
> 
>     }
> .....
> 
> Then it won't crash during the initialization. You can see the debug code 
> doesn't do anything significant except it uses the stack. But it still 
> crashes when I start using JS_CompileScript.
> 
> With the above debug statements, I saw a difference between Windows and the 
> target device. In Windows, (jsuword)(buf) % ALIGNMENT(JSString) is 0, but on 
> the target device, (jsuword)(buf) % ALIGNMENT(JSString) is 4.  Will this 
> make the two macros in jsatom.c fail? ALIGNMENT(JSString) and 
> sizeof(JSString) are both 8 in the two enviroment.
> 
> #define ALIGNMENT(t)    JS_MAX(JSVAL_ALIGN, sizeof(t))
> #define ALIGN(b,t)      ((t*) &(b)[ALIGNMENT(t) - (jsuword)(b) % 
> ALIGNMENT(t)])
> 
> Also, can anyone explain the purpose of the ALIGN macro? Any help will be 
> appreciated. Thanks a lot.
> 
> 
> 
>

.