The issue is that we are guessing as to what syntax causes the compiler to emit an extra class file.
On Fri, Aug 1, 2014 at 7:49 PM, Mark A. Flacy <[email protected]> wrote: > On Friday, August 01, 2014 05:22:39 PM William Blevins wrote: > > SCons Java doesn't need to be that fancy, but I think the root problems > can > > be solved. The SCons java tool simply doesn't get the love that some of > the > > other tools get. > > One common use case is to generate java source from the xjc tool (which > converts XML schema to java classes) for use by other java classes. > > The emitter in that case would need to parse a bindings file as well as > the XML > schema(s) that the binding file uses. However, the resulting java files > should > have no dependencies on any external libraries, so they could be compiled > as a > unit independently from anything using them. > > And there are Annotations, which can be used to (and *are* used to) > generate > source. See http://deors.wordpress.com/2011/09/26/annotation-types/ for a > discussion of how to do that. > > > > > > > I don't have the experience with the code base to know if my ideas are > > workable, so I will need some guidance. > > > > On Thu, Jul 31, 2014 at 11:04 PM, Mark A. Flacy <[email protected]> > wrote: > > > On Sunday, July 27, 2014 03:10:34 PM William Deegan wrote: > > > > William, > > > > On July 25, 2014 at 8:27:02 PM, William Blevins ( > [email protected]) > > > > wrote: > > > > > > > > Team, > > > > > > > > I want to get another thread going for SCons Java development. > > > > > > > > The SCons Java tool has a ton of error reports on Tigris including 7 > > > > priority 1 issues. At the moment, this tool doesn't stand a chance > > > > > > against > > > > > > > other Java competitors, and not because they are great tools. I > frankly > > > > hate ANT. I have used Java support from SCons and it's seriously > > > > > > painful; > > > > > > > nothing like the C++ support. Some other developers have made > > > > statements > > > > like "No one outside SCons builds Java programs more complicated than > > > > > > hello > > > > > > > world." The SCons tool framework is great, and I would really like > to > > > > > > see > > > > > > > the Java toolkit see some love. It has potential to be a hidden gem, > > > > > > and I > > > > > > > want help out with this, but I don't have the experience to do this > on > > > > my > > > > own, so firstly I'd like to list some of the biggest hurdles to users > > > > > > SCons > > > > > > > Java. I'm not gonna try and propose any solutions at the moment. I > > > > just > > > > want to see if I can get the group thinking about the problems. > > > > > > > > 1. Adding resource files to a jar causes SCons > > > > segfault: http://scons.tigris.org/issues/show_bug.cgi?id=2550 > > > > > > > > I have firsthand experience with this bug. The only way I could > figure > > > > > > out > > > > > > > how to workaround it was to make a separate jar just for resources. > > > > > > > > 2. Java emitter almost never gets the java output correct. > > > > > > > > One of the many things I hate about ANT is that ANT is stupid. It > > > > always > > > > executes a build even if code is up-to-date and I usually have to > > > > explicitly clean. SCons COULD resolve both problems if the emitters > > > > worked. The only way to get remotely consistent working build is to > > > > call > > > > Jar( 'buildDir' ) when everyone wants to do Jar( [ 'class1', ... > > > > > > 'classN' ] > > > > > > > ). > > > > > > > > 3. Dependencies: > > > > > > > > SCons does not automatically add classpath items as dependencies. > Why > > > > > > do I > > > > > > > need to do this manually? This is what SCons does! It's the heart > and > > > > soul! > > > > > > > > I believe this is because of item #6. > > > > > > > > 4. Consistency: > > > > > > > > Classpath tokens (among other items) do not behave the same as other > > > > builders. Example: I cannot use "#jar/item.jar" in the classpath > without > > > > expanding via something like File(...).get_path(). > > > > > > > > 5. Interfaces: > > > > > > > > Java(...) parameters and internal handling aren't intuitive and only > > > > > > handles > > > > > > > sources = 'directory' correctly. It doesn't do lists of java files > or > > > > > > list > > > > > > > of directories in a sane manner. > > > > http://scons.tigris.org/issues/show_bug.cgi?id=1772 > > > > > > > > Personally, I don't think that Java and Jar should be separate > > > > functions. > > > > > > > > How do you get to the classes then? What about Javah! I have an > idea, > > > > > > > > but that's outside the scope of this rant. > > > > > > > > 6. Performance: > > > > > > > > The dependency structure for Java exposes class files in a way that > > > > > > creates > > > > > > > tons of false positives. > > > > > > > > SCons current: > > > > > > > > classes1 = Java(...) > > > > > > > > classes2 = Java(...) > > > > > > > > Depends( classes2, classes1 ) # O( N^2 ) dependency graph with tons > of > > > > > > false > > > > > > > positives > > > > > > > > SCons if I have anything useful to say about it > > > > > > > > jar1 = Jar( classes1 ) > > > > > > > > jar2 = Jar( classes2 ) > > > > > > > > Depends( jar2, jar1 ) # O( 1 ) which obviously fails in parallel > builds > > > > currently. > > > > > > > > I am currently data mining a production Java codebase to prove my > point. > > > > Dirk and I have already discussed this issue somewhat; thanks Dirk :) > > > > > > > > This actually causes the Task Master thread to get blocked on large > jars > > > > reducing parallel efficiency in builds to None. > > > > > > > > > > > > The main issue here (if I understand SCons’ internals enough) is that > > > > SCons’s doing all dependencies on a per file basis. For many types of > > > > builds that works fine. For Java (building jars, and other issues) > and > > > > > > some > > > > > > > other types of builds, that’s very inefficient. > > > > > > > > There’s no “blob” of files where you have N inputs and M outputs, and > > > > > > thus > > > > > > > you get the N*M arcs in the graph. > > > > > > > > Currently the only similar but not really similar enough is the Dir() > > > > > > Node > > > > > > > type. But that has it’s own problems, which could be solved by a N*M > > > > > > type > > > > > > > node. > > > > > > > > > > > > > > > > Other Java issues could likely be resolved building on top of such a > new > > > > Node type. > > > > > > > > Though resolving the anonymous and inner classes in a java file > creating > > > > more than one class file and what it might be named is also still an > > > > > > issue > > > > > > > which the scanner and emitter try to solve by parsing the java files > and > > > > figuring out the proper naming. This of course is not (as I > understand > > > > > > it) > > > > > > > formally defined as part of the java language and thus is a per > compiler > > > > implementation detail. > > > > > > In my opinion, you are wasting your time. > > > > > > The way java produces artifacts is so different from the model that > SCons > > > "expects" that you are attempting to cram an elephant down a shrew's > > > throat. > > > (or attempting to feed a Great White shark with ants, if you prefer) to > > > get > > > this to work. > > > > > > SCons works *great* when there's one output per input, especially when > you > > > can > > > deduce the output name from the input name and little else. It also > works > > > great when it is fairly cheap to determine what files a given file > depends > > > upon. > > > > > > Sadly, neither of those conditions exist with java source. > > > > > > > > > Between 2003 and 2010, I developed and maintained a python based build > > > tool > > > for a Java project that contained ~10K java source files. It would > > > analyse the > > > java source files to figure out the package-level compile dependencies > and > > > then > > > send lists of files to be compiled as a unit to a persistent compile > > > server (in > > > fact, you could run multiple compile servers at once to get a large > degree > > > of > > > parallelism). It would then analyze the generated class files to see > if > > > the > > > total public/protected interface for the package changed, preventing > > > recompiles if all you did was change an implementation detail versus a > > > visible > > > method or attribute. > > > > > > You could also register various hooks against packages (such as run > rmic) > > > if > > > the package compiled correctly. We did some funky stuff with > > > autogenerating > > > WSDL from java source and then generate client classes from the WSDL > and > > > compiling those classes also. Almost all of that was data driven. It > did > > > other neat stuff that I don't remember off the top of my head, but I've > > > got all > > > the source sitting around in various tla/hg repositories. > > > > > > Nobody uses it any more. Even me, and I thought about providing some > it > > > in an > > > open source build tool. > > > > > > For our Windows users, it was faster to nuke the output directories and > > > recompile everything in one invocation of javac. (Well, 2 invocations > > > since > > > some of the funky stuff was to use the .class files from the first > compile > > > to > > > generate the wsdl and use *that* wsdl to generate java source as part > of > > > the > > > second bulk compile.) Most of the time difference had to do with the > way > > > the > > > python tool talked to the compile processes by sending the list of file > > > names > > > through a pipe to the other process and then flushing the pipe. The > rest > > > had > > > to do with the time spent parsing the files (and I maintained a cache > of > > > parsed > > > file information that contained the last mtime of the source files and > > > would not > > > process a file whose mtime was the same as what was recorded). > > > > > > For our Linux users (me, for one), it was not quite a wash to change > the > > > behavior but the delta wasn't enough to worry about. > > > > > > I'm more than willing to discuss this and also to be proven wrong. > > > > > > -- > > > Mark A. Flacy > > > _______________________________________________ > > > Scons-dev mailing list > > > [email protected] > > > http://two.pairlist.net/mailman/listinfo/scons-dev > -- > Mark A. Flacy > _______________________________________________ > Scons-dev mailing list > [email protected] > http://two.pairlist.net/mailman/listinfo/scons-dev >
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