Incremental java compile AKA javac print compile dependencies

Joshua Maurice joshuamaurice at
Tue May 25 06:47:37 UTC 2010

Thank you. I will ask that group.

However, your suggestion of the class files doesn't quite fit what I want to
do. Using the information from class files, (ignoring the constant problem),
(without great modification), will only work if the build cascades endlessly
downstream. I am specifically trying to make a system where the cascade will
terminate when no further recompiles downstream are required. To this end,
the information in the class files is woefully insufficient. Ex: C extends
B. B extends A. A declares member field x. Class D uses C.x. I'm pretty sure
that in D's class file, A and B are not mentioned. Some change to B could
introduce a field named x, "hiding" A.x, potentially changing the meaning
and compile of D, potentially even resulting in a clean build failure, but
this "incremental" build would silently call a success.

Also, the JavaFileMananger idea will not work for the same reason that
-verbose as is will not work. I need / want this information on a per java
file basis, but javac "caches" referenced class files, only loading them
once, so neither will give me what I need.

PS: Is there a non-arrogant way to suggest reading the discussion, as it contains most of this discussion
already, without sounding like a self absorbed jerk who thinks his time is
more important than everyone else's? Probably not. I'll ask compiler-dev.

On Mon, May 24, 2010 at 9:29 PM, Jonathan Gibbons <
jonathan.gibbons at> wrote:

> Joshua,
> This question is better asked on compiler-dev at
> There are various ways you can get the information you are asking, in a
> single invocation of the compiler and without changing the compiler.
> One way would be to invoke the compiler via the JSR 199 API. You can
> provide your own JavaFileManager which can keep track of files read and
> written by the compiler. For the class files that are written, you can
> analyze the class files to determine all the classes that are referenced by
> that class file. Class files also identify the source files that they come
> from. That should be enough to get you almost all the information that you
> need. The only information you'll miss using that technique is inlined
> constants.
> -- Jon G
> On 05/24/2010 07:23 PM, Joshua Maurice wrote:
>> I'm sorry. I'm new to this list, and I'm not sure if this is the
>> appropriate
>> forum. I was looking at the javac source code, and I am now looking for
>> help
>> or guidance. Specifically, I want to create an incrementally correct build
>> system for java, preferably without having to (re)write a Java compiler. I
>> need some additional information to be printed from javac to get full
>> dependency information. Please see:
>> for a detailed discussion. The short version is that -verbose output
>> almost
>> is what I need. I need to know the full list of class files loaded for
>> each
>> java file being compiled, and the full list of java files in the compile
>> used by each java file being compiled; that is, the full list of java file
>> and class file \compile\ dependencies of each java file in the compile.
>> One
>> can already get this information by calling javac once on the set of
>> interested java files to do the compile, then an additional java -verbose
>> once per java file to get the dependency information.
>> However, calling javac so many times is quite slow, and unnecessary. I
>> would
>> like to enhance javac to print out this dependency information with one
>> invocation aka without resorting to calling javac once per java file, and
>> preferably get this change into the actual official released javac.
>> PS: Yes this information on its own is insufficient to do an incrementally
>> correct java compile. However, when combined with Ghost Dependencies
>> (please
>> see:
>> ), I think that this would actually work. I have some tests to this effect
>> already with my proposed system which currently calls javac once per java
>> file to get the compile dependency information.

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