Hi Daniel, thanks for the report.

On Monday 15 August 2011, Daniel Richard wrote:
> I am using Automake 1.11.1, and have recently encountered a subtle issue
> that causes compilation of some Java programs to fail.
> 
> Here is a typical build failure, produced from a minimal test case I've
> assembled, using OpenJDK on Ubuntu's Natty release:
> 
> make[3]: Entering directory `/tmp/automake-java-bug/org/gnu/bug'
> CLASSPATH=../../..:./../../..:$CLASSPATH javac -d ../../..    Library.java Application.java
> ./Library.java:5: duplicate class: org.gnu.bug.Library
> public class Library
>        ^
> Application.java:9: cannot access Library
> bad class file: RegularFileObject[./Library.java]
> file does not contain class Library
> Please remove or make sure it appears in the correct subdirectory of the classpath.
> 		Library lib = new Library();
> 		^
> 2 errors
> make[3]: *** [classdist_noinst.stamp] Error 1
> 
> 
> If I copy-and-paste the javac invocation, edit it slightly, and run
> it...
> 
>     env CLASSPATH=../../..:./../../..: javac -d ../../.. Library.java Application.java
> 
> ...I get the same error. However, if I remove that trailing colon from
> CLASSPATH, and try it again...
> 
>     env CLASSPATH=../../..:./../../.. javac -d ../../.. Library.java Application.java
> 
> ...compilation succeeds. If I invoke the above build with
> 
>     env CLASSPATH=/does-not-exist make
> 
> then compilation likewise succeeds.
> 
> Note that I do not have CLASSPATH set in my environment. It would appear
> that a trailing colon in the CLASSPATH environment variable has a
> special meaning attached to it, which makes Automake's use of
> CLASSPATH=mumblemumble:$$CLASSPATH in makefiles problematic.
> 
> (The straightforward solution would be to replace that construct with
> CLASSPATH=mumblemumble$${CLASSPATH:+:$$CLASSPATH}, but whether all
> shells can handle that is an open question.)
>
Luckily, as far as I know, the above construct should be portable to all
non-museum shells.  So I've used it with only a minor modification (with
the only purpose of making the contruct slighlty clearer):

  CLASSPATH=mumblemumble$${CLASSPATH:+":$$CLASSPATH"}

> Attached is a tarball containing the minimal test case.
> 
I can reproduce the problem using your test case, and fix it using your
suggestion.  I've preparad the attached patch, which I will push in a
couple of days if there are no further comments.

BTW, are you the same "Daniel Richard G." listed in THANKS with the address
"danielg@teragram.com"?  If yes, should I update your address there?

Thanks,
  Stefano