> 1.  What's up with the 512 byte header on Unix?  The code I 
> wrote to deal 
> with it was in routines that did checking, but not the main 
> routine that 
> actually reads and understands the image.  This makes me a bit 
> nervous.  The main code looks as if it automatically seeks 512 bytes 
> forward if it runs into trouble, and I guess the file is read 
> from this 
> offset.  Is that really all there is to it?  Obviously a 
> messup on this 
> could be catastrophic.
> 
> The unix code redefines sqImageFileStartLocation and claims this is 
> automatically used.  But the only caller I found (in 
> interp.c) uses it when 
> writing, not reading.  This is just as well, since it's hard 
> coded to 512, 
> while on Unix some files have the extra header and some 
> don't.  All this 
> left me with an uneasy feeling.

I vaguely remember a thread from a few years ago about supporting
self running images by adding #!/your/path/squeak.exe at offset 0.

-david