flex compiler error (warning) message in flex ant task

Question

I have following warnings if I compile our flex project with the ant task from the flex sdk. Does anyone have an idea where this comes from and why this happens and if I can safely ignore it? (The swf file itself seems to get created without an actual error)

[mxmlc] The args attribute is deprecated. Please use nested arg elements.
[mxmlc] Loading configuration file /home/jrose/SDKs/flex_sdk_3-1/frameworks/flex-config.xml
[mxmlc] Locking assertion failure.  Backtrace:
[mxmlc] #0 /usr/lib/libxcb-xlib.so.0 [0x786057c7]
[mxmlc] #1 /usr/lib/libxcb-xlib.so.0(xcb_xlib_unlock+0x31) [0x78605891]
[mxmlc] #2 /usr/lib/libX11.so.6(_XReply+0x254) [0x77053494]
[mxmlc] #3 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/xawt/libmawt.so [0x77e6ddce]
[mxmlc] #4 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/xawt/libmawt.so [0x77e57d77]
[mxmlc] #5 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/xawt/libmawt.so [0x77e57ef3]
[mxmlc] #6 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/xawt/libmawt.so(Java_sun_awt_X11GraphicsEnvironment_initDisplay+0x26) [0x77e58136]
[mxmlc] #7 [0xb1411008]
[mxmlc] #8 [0xb140ab6b]
[mxmlc] #9 [0xb140ab6b]
[mxmlc] #10 [0xb1408236]
[mxmlc] #11 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/server/libjvm.so [0xb76a3eec]
[mxmlc] #12 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/server/libjvm.so [0xb7873ae8]
[mxmlc] #13 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/server/libjvm.so [0xb76a3d1f]
[mxmlc] #14 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/server/libjvm.so(JVM_DoPrivileged+0x32d) [0xb770182d]
[mxmlc] #15 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/libjava.so(Java_java_security_AccessController_doPrivileged__Ljava_security_PrivilegedAction_2+0x3d) [0xb73a730d]
[mxmlc] #16 [0xb1410898]
[mxmlc] #17 [0xb140aa94]
[mxmlc] #18 [0xb1408236]
[mxmlc] #19 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/server/libjvm.so [0xb76a3eec]
[mxmlc] Locking assertion failure.  Backtrace:
[mxmlc] #0 /usr/lib/libxcb-xlib.so.0 [0x786057c7]
[mxmlc] #1 /usr/lib/libxcb-xlib.so.0(xcb_xlib_lock+0x2e) [0x7860596e]
[mxmlc] #2 /usr/lib/libX11.so.6 [0x77052619]
[mxmlc] #3 /usr/lib/libX11.so.6(XGetVisualInfo+0x26) [0x77048666]
[mxmlc] #4 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/xawt/libmawt.so [0x77e570b9]
[mxmlc] #5 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/xawt/libmawt.so [0x77e57303]
[mxmlc] #6 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/xawt/libmawt.so [0x77e57fa1]
[mxmlc] #7 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/xawt/libmawt.so(Java_sun_awt_X11GraphicsEnvironment_initDisplay+0x26) [0x77e58136]
[mxmlc] #8 [0xb1411008]
[mxmlc] #9 [0xb140ab6b]
[mxmlc] #10 [0xb140ab6b]
[mxmlc] #11 [0xb1408236]
[mxmlc] #12 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/server/libjvm.so [0xb76a3eec]
[mxmlc] #13 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/server/libjvm.so [0xb7873ae8]
[mxmlc] #14 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/server/libjvm.so [0xb76a3d1f]
[mxmlc] #15 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/server/libjvm.so(JVM_DoPrivileged+0x32d) [0xb770182d]
[mxmlc] #16 /usr/lib/jvm/java-1.5.0-sun-1.5.0.16/jre/lib/i386/libjava.so(Java_java_security_AccessController_doPrivileged__Ljava_security_PrivilegedAction_2+0x3d) [0xb73a730d]
[mxmlc] #17 [0xb1410898]
[mxmlc] #18 [0xb140aa94]
[mxmlc] #19 [0xb1408236]

Ant target

<target name="compile-flex-swf" description="creates swf file">
    <mxmlc file="${basedir}/flex_src/company_gui.mxml" 
        keep-generated-actionscript="false" 
        output="${basedir}/target/${ant.project.name}.swf" 
        fork="true" 
        debug="${flex.debug}" 
        services="${basedir}/WebContent/WEB-INF/flex/services-config.xml" 
        actionscript-file-encoding="UTF-8" 
        optimize="true">

        <load-config filename="${FLEX_HOME}/frameworks/flex-config.xml" />
        <context-root>company</context-root>
        <compiler.library-path dir="${LCDS_HOME}/resources/frameworks" append="true">
            <include name="libs/fds.swc" />
        </compiler.library-path>
        <compiler.library-path dir="../company_flex/target" append="true">
            <include name="*.swc" />
        </compiler.library-path>
    </mxmlc>
</target>

Answer 1

Those backtraces really have nothing to do with flex or ant. It really is just an interaction between AWT and XCB. You can find more information with the sun bug 6532373 or the Xlib bug 11390. There are workarounds, but I don't think they are necessary (other than removing those nasty messages).