[fpc-devel] PPU version checking

[Hans-Peter Diettrich]

Tomas Hajny schrieb:
>> If you'd disable the check you would not be able to use e.g. a 2.4 unit
>> with 2.6, because the PPU format is different and thus you'd definitely
>> (not just perhaps!) get errors when the compiler reads the PPU file.
> 
> In other words: _If_ someone is motivated enough for such a task, it would
> be possible to create a convertor from one PPU version to another (and I
> don't mean a "convertor" only changing the version number but something
> that really loads the original format of the particular original version
> and stores the data in the new format with new version). I don't think any
> of the core developers would be interested in such a task (at least not
> just for fun because it would not be much fun most likely), but I don't
> want to talk for others.
> 
> Moreover, note that in addition to PPU version number you also have
> dependencies related changes in RTL and packages. In other words, you
> would need to convert the originally used compiled RTL+packages units this
> way together with your own (compiled) units in order to be able to use
> those units with the new compiler.

This is where a decompiler could help. It reconstructs the source code 
from the old PPU, which then can be adoptede and compiled with a newer 
version.

A PPU decompiler is somewhat easy to create, as is for object files of 
other OO languages, in contrast to an decompiler for executables of an 
unknown (or multiple) compilers. I wrote decompilers for many compilers, 
but never for Pascal because I wanted to protect the work of the users 
of this language.

DoDi