Headless property is baked in, can no longer run heady

[kristofdho]

Describe the issue
The awt invocation plugin causes the headless property to be stored at build-time, which means you can no longer switch between headless and heady execution at runtime. Since on windows, -Djava.awt.headless=true is set by native-image itself, this breaks any heady application.

The plugin seems to be directed at unix environments, as that's also the only awt support that's already added, so it might make sense to only conditionally add the plugin if we're targetting unix.

Additionally I think it's not preferable to have to decide at build-time if the application will run headless or heady.

The invocation plugin this is about:

graal/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/snippets/SubstrateGraphBuilderPlugins.java

Lines 1033 to 1048 in 6fc5aaf

	/*
	* To prevent AWT linkage error that happens with 'awt_headless' in headless mode, we eliminate
	* native methods that depend on 'awt_xawt' library in the call-tree.
	*/
	private static void registerAWTPlugins(InvocationPlugins plugins) {
	Registration r = new Registration(plugins, GraphicsEnvironment.class);
	r.register0("isHeadless", new InvocationPlugin() {
	@SuppressWarnings("unchecked")
	@Override
	public boolean apply(GraphBuilderContext b, ResolvedJavaMethod targetMethod, Receiver receiver) {
	boolean isHeadless = GraphicsEnvironment.isHeadless();
	b.addPush(JavaKind.Boolean, ConstantNode.forBoolean(isHeadless));
	return true;
	}
	});
	}

Steps to reproduce the issue

• run any natively compiled windows app with -Djava.awt.headless=false and it will still be headless

Describe GraalVM and your environment:

• GraalVM version: 72439a3 (as good as up to date with master)
• JDK major version: 11
• OS: Windows 10
• Architecture: x64

[munishchouhan]

@kristofdho please provide reproducer

[kristofdho]

file: BakedInHeadlessPoc.java

import java.awt.GraphicsEnvironment;

class BakedInHeadlessPoc {
    public static void main(String[] args) throws Exception {
		System.out.println(GraphicsEnvironment.isHeadless());
	}
}

compile & build:

javac BakedInHeadlessPoc.java
native-image -H:Name=BakedInHeadlessPoc -H:Class=BakedInHeadlessPoc --verbose --no-fallback

run compiled binary:

> BakedInHeadlessPoc.exe
true

> BakedInHeadlessPoc.exe -Djava.awt.headless=true
true

> BakedInHeadlessPoc.exe -Djava.awt.headless=false
true

expected output:

> BakedInHeadlessPoc.exe
false

> BakedInHeadlessPoc.exe -Djava.awt.headless=true
true

> BakedInHeadlessPoc.exe -Djava.awt.headless=false
false

marking GraphicsEnvironment for run-time initialization doesn't work and crashes the build, as the plugin appears to require it to be initialized at build-time.

suggested fix in #3068

[kristofdho]

Should this not be included in the 21.0 milestone as well? It is regression so it would make sense.
There is quite some stuff depending on this flag as well, like anything javafx, or awt functionality. I personally depend on both so this would render 21.0 unusable for me.

[kristofdho]

I would like to restate the importance of this regression for us. Could I have some context on why this is not making 21.0, and what a possible workaround would be?

[pejovica]

@kristofdho, I wouldn't necessarily call this a regression, because AWT is not yet supported on Windows (see #3084), but I also agree that this plugin should not be needed.

So until this is fixed, you can pass -Djava.awt.headless=false to native-image when building an image as a workaround, i.e.:

> native-image -H:Name=BakedInHeadlessPoc -H:Class=BakedInHeadlessPoc --verbose --no-fallback -Djava.awt.headless=false
...

> BakedInHeadlessPoc
false

> BakedInHeadlessPoc -Djava.awt.headless=true
false

> BakedInHeadlessPoc -Djava.awt.headless=false
false

[zakkak]

Can someone please add the platform-windows label to this issue?

[munishchouhan]

@zakkak done

[zakkak]

Thank you @mcraj017 !