On Mon, Mar 04, 2013 at 09:25:02PM +0100, Marco van de Voort wrote: > In our previous episode, Henry Vermaak said: > > > > I just add all the objects to a variable in a Makefile. > > > > > > > > The result is that I have a 27000 line c library that compiles in *half* > > > > the time it takes to compile a 4000 line lazarus program because my c > > > > lib can be built with make -j 9. > > > > > > I'm not exactly sure what this proves. The C situation is not equivalent > > > to > > > the Pascal situation, the latter trying to make sure all (Pascal level > > > symbols) are there before the linker. > > > > What I'm trying to say is that gcc is going 3 times faster on my quad > > core machine because of the build system, not because they've turned > > their compiler into a multi-threaded clusterfsck. > > IMHO a threading clusterfsck is preferable to a forking clusterfck :-)
My gut feeling would be that the complexity and potential bugs/races don't make up for the speed, but maybe a threaded compiler gains a lot more than I imagine. Are there any multi-threaded compilers around for comparison? > Yes. But is that incremental? It is fun to speed up a full build, but in > reality developers are more likely to do a partial one. Ever pressed F9 > after a small change in Delphi? The app starts nearly immediately, if > the change wasn't too deep in the hierarchy of dependencies. > > But compilation units in C have weaker(no) coherence than in (modular) > Pascal, and C does > not have an auto build system. All dependencies are done manually. > (sometimes assisted with semi automated tools) > > This means you need to manually specify in the build system which > compilation unit depends on which headers. And this is also why in C/C++ > inline functions are in the header, so that this model is persistent, since > most builds are not full, but incremental. As you probably know, you can use -MD and variants with gcc, which outputs dependency files for make, that you then include in the Makefile. If you add, e.g. -MMD to the CFLAGS, these dependencies are generated as a side effect of the compilation process, so it's not a separate step. As a result, partial builds work really well, and can be parallelized as usual. No manual work involved. Henry _______________________________________________ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
