kicad-developers team mailing list archive

[jp charras <jp.charras@xxxxxxxxxx>]

Le 01/05/2016 à 05:39, Chris Pavlina a écrit :
> I have a pretty specific question about some relatively old code that
> intersects with what I'm working on now. Dick was the original author, not sure
> if he'd remember... -
> 
> pcbnew/legacy_plugin.h:
> 33  #define FOOTPRINT_LIBRARY_HEADER       "PCBNEW-LibModule-V1"
> 34  #define FOOTPRINT_LIBRARY_HEADER_CNT   18
> 
> 
> FOOTPRINT_LIBRARY_HEADER_CNT is being used as a length in comparisons using
> strncmp(). The length does not match, however, as "PCBNEW-LibModule-V1" is 19
> characters long, not 18. At first I thought this was a simple mistake, and
> replaced FOOTPRINT_LIBRARY_HEADER_CNT with strlen(FOOTPRINT_LIBRARY_HEADER),
> which eliminates the possibility of a miscount (and for the micro-optimizers
> out there, all the compilers I've used optimize strlen(literal) ;).
> 
> But then it occurs to me that it *might* have been intentional, as comparing
> with a length of 18 will compare everything but the version number, which may
> have been desired.
> 
> Anyone willing to have a look at the code that uses this, and see what they
> think the intended use was? Has there ever been a V2?
> 

It *is* intentional.
PCBNEW-LibModule-V1 is the current identifier of legacy libraries.
PCBNEW-LibModule-Vnn was planned for future version.
Obviously, it did not happen because footprint libraries are no more files.

The first 18 letters are used to know if a file is a kicad footprint file or not.
Now, they are used to select the plugin, when trying to automatically select a plugin to import a
footprint file, and using strlen(FOOTPRINT_LIBRARY_HEADER) is not good in this case.

Be careful when changing code which read old files.
You easily can break compatibility of very old files (for instance 10 year old: you cannot be sure
the identifier is PCBNEW-LibModule-V1. It can be PCBNEW-LibModule-Version 1 of some other).
To change this kind of (good) code, you must have very good reasons.

-- 
Jean-Pierre CHARRAS