Name: tb29552 Date: 01/08/98


Create three .java files:

A.java:

  class A{
    B b;
  }

B.java:

  class B{
    C c;
  }

C.java:

  class C{
  }

and place them all in the same directory.
Then compile using:
  javac -d targetdir -depend A.java

All three classfiles are (correctly) compiled
into targetdir.

Then recompile (without making any changes)
using:
  javac -d targetdir -depend A.java

All three classfiles are (incorrectly) recompiled.
No new compilation should be necessary as
all the classfiles are up to date. If class files
exist in the same directory as the java files
unecessary recompilation does not take place.

The problem does not occur if you do not use
the -d targetdir argument (ie. build the class
files into the same place as the java files). This
has been tested and shown to be because
regardless of whether the -d argument has been
used the compiler is checking in the same
directory as the java files for the class files when
deciding if the class file is out of date (and so
needs to be recompiled).

Although it correctly places the class files in a
different directory it does not check in that
directory when looking for existing class files.

If you are compiling into a different directory with
the -d argument it never finds the class files and
so always considers them to be out of date and
rebuilds everything each time.

This is proving to be a very costly problem on
large projects where recompilation that should
take a minute at most is taking up to an hour.

The problem is reproducable on NT4.0 and
Unix using javac supplied with jdk1.1.x and
jdk1.2Beta2.

This could also be a possible solution for Bug
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