Re: Interpreter not building correct byte code

[David Jones <drj@...>]

On 22 Dec 2006, at 18:32, Tom Bates wrote:

> >> At the moment, the interpreter does not build correct code from  
> source
>
> >
>
> >What errors does the compiler give?
>
> 	
>
> Running on the prototype hardware (i.e.68331), the compiler/ 
> interpreter generates no errors, i.e. luaL_loadbuffer returns 0.  
> However, lua_pcall then either causes a fault or returns a bogus  
> error message like “attempt to perform arithmetic on a string  
> value”. To track this down, I worked my way down into the VM code  
> and found that the instructions there do not match what is  
> generated by the luac compiler running in Visual Studio 6 under  
> Windows 2000 Pro. The first few instructions look good, but the  
> rest is no good (e.g. no return instruction anywhere).

The bytecodes produced by luac are endian dependent (as well as  
dependent on word-width and floating point format).

An Intel PC is little-endian, a 68K is big-endian.  You can either  
swab offline, using Kein-Hong Man's ChunkSpy http://luaforge.net/ 
projects/chunkspy/ , or rewrite lundump.c to use the other (or  
either) endianness.  I think LHF posted a modified lundump.c to the  
list last year.

This useful fact about luac's bytecodes is documented in its manual:  
http://www.lua.org/manual/5.1/luac.html

I hope that helps.  Good look with re-alloc.

Cheers,
 drj