[fpc-devel] Comparison FPC 2.6.2 - Delphi 7

[Hans-Peter Diettrich]

Henry Vermaak schrieb:

> I'm trying to ascertain if this is even possible (the c-style,
> file-at-a-time compilation, using make to handle multiple processes).
> Do you think it's possible, then?

Yes and no. It would mean to create kind of header files for the Pascal 
units, usable to compile the units independently. No problem at a first 
glance, the Interface is the equivalent of an C header file, and the 
Uses lists are equivalent to further #includes. One of the remaining 
problems are the lost unit qualifiers, so that external references in 
the object files cannot be safely resolved.

But in fact above is what FPC already does! When it encounters a Uses 
list, it loads the according PPU or, if not available or outdated, 
compiles the requested unit. Thus the PPU files already *are* the 
equivalent of the C header files. Plus the bonus that every "header" has 
to be loaded only once, not for every single module to be compiled by an 
C compiler.

The problem IMO is the long list of units waiting for their dependencies 
loaded, before the first unit can be compiled at all (top-down). More 
efficient were bottom-up compilation, starting with the units with only 
few dependencies, so that compilation could start while the disk is 
stressed by loading all other PPU files, required for the compilation of 
units with more dependencies.

DoDi