Subj : Re: Bug with MSVC Linker
To   : netscape.public.mozilla.jseng
From : Phil Schwartau <pschwartau@netscape.com>
Date : Wed Mar 19 2003 01:31 pm

 > ...and now to something completly different: the implementation of the
 > js_GetLocalVariable() function in jsinterp.c:551 was changed from RC4a to
 > RC5. The implementation is now just "return JS_TRUE".

You are right; the problem was noted and addressed in this bug:
http://bugzilla.mozilla.org/show_bug.cgi?id=151066#c7

The make system for Mozilla was changed to add the option /OPT:NOICF on Windows (meaning, "do NOT 
perform identical COMDAT folding")

We also updated the js.mak and Makefile.ref systems for building our standalone JS shell:
http://bugzilla.mozilla.org/show_bug.cgi?id=160592#c3

I think you're running into the same issue -
Phil


Michael Schneider wrote:
> Hey all!
> 
> After upgrading to SpiderMonkey 1.5 RC5 we had some big trouble. One of our
> products keept crashing when a script was compiled. Besides of that, we were
> only able to reproduce this error in a build without any debug symbols.
> After some serious bug-searching we found the following:
> 
> A very simple ( ;) ) script defining a global variable (outside of a
> function) crashes the engine:
> --8<-------8<-------8<---
> var xxx
> --8<-------8<-------8<---
> 
> The reason for this is as follows:
> - In jsparse.c on line 1916 the getters & setters are read
> getter = clasp->getProperty;
> setter = clasp->setProperty;
> 
> these pointers are used a bit later in a comparison on line 2045. by the
> way, the getters and setters of our global objects are JS_PropertyStub().
> this works just fine..
> 
> ...and now to something completly different: the implementation of the
> js_GetLocalVariable() function in jsinterp.c:551 was changed from RC4a to
> RC5. The implementation is now just "return JS_TRUE".
> 
> and here comes the problem: the MSVC linker notices that the
> JS_PropertyStub() and the js_GetLocalVariable() function have the same
> signature and do exactly the same -> the linker "optimizes" one of the
> implementations away (but only, if no symbols are used, because the symbols
> do make the difference ;)), leftover remains the other. But of course both
> methods have now the same address, what makes the comparison currentGetter
> == js_GetLocalVariable become true!!!
> 
> because we are not in a function, fun is NULL ->  the parser crashes in
> jsparse.c:2053 when dereferencing fun.
> 
> as quick workaround, we changed the implementation of js_getLocalVariable(),
> so that the linker (or the compiler first) won't "optimize" it:
> 
> JSBool js_GetLocalVariable(JSContext *cx, JSObject *obj, jsval id, jsval
> *vp)
> {
>     return cx != NULL ? JS_TRUE : JS_FALSE;
> }
> 
> another approach would be to add the additional check for fun != NULL, but
> I'm not sure if we would cover all possibilities with this fix.
> what do you suggest?
> 
> 
> 
> greets,
> 
> Mike
> 
> 
> 
>

.