I am not sure about this, just something I noticed
while working on a j2seproject. I got a warning
from javac (JDK 1.5):

Note:
/tmp/testantlogging/src/testantlogging/Main.java
uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

After adding this to my build.xml:

<target name="init-macrodef-javac">
    <macrodef name="javac"
uri="http://www.netbeans.org/ns/j2se-project/1">
        <attribute name="srcdir"
default="${src.dir}"/>
        <attribute name="destdir"
default="${build.classes.dir}"/>
        <attribute name="classpath"
default="${javac.classpath}"/>
        <attribute name="debug"
default="${javac.debug}"/>
        <element name="customize" optional="true"/>
        <sequential>
            <javac srcdir="@{srcdir}"
destdir="@{destdir}" debug="@{debug}"
deprecation="${javac.deprecation}"
source="${javac.source}" target="${javac.target}"
includeantruntime="false">
                <classpath>
                    <path path="@{classpath}"/>
                </classpath>
                <compilerarg compiler="javac1.5"
value="-Xlint:unchecked"/> <!-- *ADDED* -->
                <customize/>
            </javac>
        </sequential>
    </macrodef>
</target>

I get the real messages:

Compiling 1 source file to
/tmp/testantlogging/build/classes
/tmp/testantlogging/src/testantlogging/Main.java:63:
warning: [unchecked] unchecked call to addFirst(E)
as a member of the raw type java.util.LinkedList
        stack.addFirst(name);
                      ^
/tmp/testantlogging/src/testantlogging/Main.java:86:
warning: [unchecked] unchecked call to addFirst(E)
as a member of the raw type java.util.LinkedList
        stack.addFirst(name);
                      ^
2 warnings

Frankly I have no idea what these warnings mean,
but presumably they could be important to someone
more experienced with generics. :-) If I declare
the generic type of my LinkedList in JDK 1.5
semantics, then the warnings go away (to be
replaced with many background parser errors
because our trunk javac does not grok generics!).

Anyway, seems like something we might want to turn
on by default for 1.5 users, as a complement to
-deprecation (which is apparently now an alias for
-Xlint:deprecation??), since it is not obvious how
to do the right build.xml edit.

Or we could wait for more direct support for such
flags in Ant (with proper cross-compiler support).