Re: Microchip COFF file format changes for 8-bit tools

What does this mean to gputils/gpsim/sdcc?

----- Original Message ----- 
From: "James Grosbach" <[email protected]>
Newsgroups: gmane.comp.hardware.microcontrollers.gnupic
Sent: Tuesday, July 19, 2005 3:26 AM
Subject: Microchip COFF file format changes for 8-bit tools


> Hi folks,
> 
> I'd like to give you good folks a bit of a heads up that our COFF file
> format is changing with the forthcoming (v3.00) release of MPLAB C18.
> 
> This is all information which will be documented in the updated compiler
> User's Guide, but I figured a summary might be useful to you.
> 
> Specifically, the following changes are being made:
> 
> * Magic number
> Since the file format is changing, the magic number will change so the
> new and the old formats are distinguishable from one another. The magic
> number will be changed to 0x1240.
> 
> The floating point format used is inferable from the magic number. If
> the magic number is 0x1234, the floating point format is MCHP, else it
> is IEEE. This will still result in an incorrect assumption for v2.4x
> compilers, but that is an issue currently and not something a more
> involved design would solve. This is purely an inference MPLAB will make
> based on the magic number, but again, it may be useful information to
> know what's happening.
> 
> 
> * Symbol table type information
> The n_type field in the syment data structure will be widened from 16
> bits to 32 bits to provide for the additional content needed to encode
> for additional type information. This will widen all symbol table
> entries, including auxiliary entries, by 16 bits. All other symbol table
> entry structures will need 16 bits of padding added to the end of the
> structure.
> 
> For the n_type field, the base type and the derived type sub-fields will 
> each be expanded by one bit to encode additional information.
> 
> The additional base type values representable are:
> 16  T_LNGDOUBLE Long double floating point (unused by C18)
> 17  T_SLONG   Short long integer
> 18  T_USLONG  Unsigned short long integer
> 
> The derived type values will be:
> 1 DT_RAMPTR (was DT_PTR, now exclusively references data memory)
> 4 DT_ROMPTR Pointer to program memory
> 
> * Version information
> The vstamp field in the optional header is currently unused by Microchip
> applications and is reserved for version stamp information.
> This field will be used to specify version information for the
> generating application. For linked files, the version of the linker will
> be stored. 
> 
> The field will be widened from 16 bits to 32 bits.
> 
> Microchip version numbers are of the form XX.YY.ZZ. The version stamp
> will be derived as vstamp=XX*10000+YY*100+ZZ. A version stamp value of 
> zero indicates that a version number is not specified.
> 
> I hope this information will prove useful to you. If you have any
> questions, please feel free to contact me and I'll do my best to answer.
> I am subscribed to this mailing list, although I check it somewhat
> infrequently, so for any on-list questions I would greatly appreciate it
> if you would include my address as a CC to help make sure I don't miss
> it.
> 
> 
> Regards,
>  Jim Grosbach
> 
> -- 
> James Grosbach
> Principal Compiler Engineer
> Microchip Technology