Shriramana Sharma wrote: > I learnt from the good people on this list that usage of: > > -fdata-sections -ffunction-sections -Wl,--gc-sections > > will ensure that only those sections of object modules get linked to the > target which are actually used in the target. > > Recently I was musing on whether I can use this when I recompile the Qt > 4 libraries for static linking. But the thing is that the Qt libraries > are already very optimized in this aspect -- in that there is a separate > source file per class and consequently a separate object file per class. > > However I was wondering whether even then I could do my > hyper-optimization because I will be using only a small number of > functions in each class. It is highly unlikely that I (or anyone else) > is going to use all member functions of a class. > > Then I thought how I could possibly prevent linking a function which was > part of a class definition. To my understanding at runtime whenever a > class is loaded into memory (I'm not talking about the individual > instances) its members including functions are all loaded into memory. > If a particular function is not present for loading, wouldn't that be a > fatal error? > > So the long and short of it is, are these options useful to filter out > unused class members or not? Possibly. C++ methods aren't really any different from C functions in terms of object code, so it's conceivable that they could be omitted if the aren't used. OTOH, I suspect that virtual methods are always "used" when intialising the virtual method table, so it's less likely that they could be omitted. If you want a definite answer, test it. -- Glynn Clements <glynn@xxxxxxxxxxxxxxxxxx> - To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
