Subj : Re: Project Settings:  Struct Member Alignment
To   : netscape.public.mozilla.jseng
From : John Bandhauer <jband_mozilla@rattlebrain.com>
Date : Thu Oct 16 2003 08:19 pm

Like brendan said, it might just work if you recompile the engine with 1 
byte packing. Might not.

However, (for the MS compiler, at least) you should be able to use 
'#pragma pack' blocks around the #includes of jJS headers in your code 
to tell the compiler that the JS structs expect 4 byte alignment - even 
if all your other structs are packed tighter. The compiler is supposed 
to be smart enough to know to do the right thing with any subsequent use 
of a struct type declared with a given packing.

Something like...

#pragma pack(push, 4)
#include "jsapi.h"
#pragma pack(pop)

Not that I've done that with SpiderMonkey, but I'd expect something like 
that to work :)

See: 
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccore98/HTML/_predir_pack.asp

John.

Brendan Eich wrote:

> Izman wrote:
> 
>> I am trying to implement the js engine into a project that must be 
>> compiled
>> with a struct member alignment of 1 byte.  The default struct member
>> alignment is 8 bytes for the js projects.  The original project will not
>> work properly with the js engine as is.  The js portion of the original
>> project works ok when I change the struct member alignment to 8 bytes
>> (matching the js engine) but then other parts of the project do not 
>> function
>> properly.  This issue has occurred with all versions of the js engine 
>> I have
>> downloaded (including the current one).  My questions are:
>>
>> Will the js projects compile and function normally if I change the js
>> project settings to a struct member alignment of 1 byte?
>>
> 
> I don't know.   You'd have to test.  I would be interested in your 
> results, but you will have to be willing to debug, give crash stack 
> traces, etc.
> 
>>  If I cannot change
>> the struct member alignment of the js projects to 1 byte, is there a 
>> proper
>> method of implementing the engine into a project that must be compiled 
>> with
>> a struct member alignment of 1 byte and what is that method?
>>  
>>
> 
> I have non-specific memories of people doing that (on Mac OS 9 or older, 
> with CodeWarrior).  Anyone else?
> 
> /be
> 
>> Thank you in advance for any help that is provided.
>>
>> Izman
>>
>>
>>  
>>
>

.