Question about Native Image debugging

[SetoKaiba]

The doc only mentioned that the quarkus.native.debug.enabled. What does it do actually? Does it add the -g to javac? Does it add the -g to native-image? Does it add the -O0,-H:-OmitInlinedMethodDebugLineInfo to native-image?

[quarkus-bot[bot]]

/cc @zakkak (native-image)

[zakkak]

Hello @SetoKaiba,

What does it do actually?

That depends on the Quarkus and Mandrel/GraalVM version.

To see what actually happens follow the io.quarkus.deployment.pkg.NativeConfig.Debug#enabled references in the source code, e.g.:

quarkus/core/deployment/src/main/java/io/quarkus/deployment/pkg/steps/NativeImageBuildStep.java

Lines 746 to 758 in 45a7c9d

	if (nativeConfig.debug().enabled() && graalVMVersion.compareTo(GraalVM.Version.VERSION_23_0_0) >= 0) {
	/*
	* Instruct GraalVM / Mandrel to keep more accurate information about source locations when generating
	* debug info for debugging and monitoring tools. This parameter may break compatibility with Truffle.
	* Affected users should explicitly pass {@code -H:-TrackNodeSourcePosition} through
	* {@code quarkus.native.additional-build-args} to override it.
	*
	* See https://github.com/quarkusio/quarkus/issues/30772 for more details.
	*/
	addExperimentalVMOption(nativeImageArgs, "-H:+TrackNodeSourcePosition");
	/* See https://github.com/Karm/mandrel-integration-tests/issues/154 for more details. */
	addExperimentalVMOption(nativeImageArgs, "-H:+DebugCodeInfoUseSourceMappings");
	}

Does it add the -g to javac?

No, but there is a feature request for this, see #31218

Does it add the -g to native-image?

Yes

Does it add the -O0,-H:-OmitInlinedMethodDebugLineInfo to native-image?

No, we don't want to pass -O0 since we want users to debug an instance of their application as close to what they will deploy as possible. In our opinion -O0 should only be used when necessary.

-H:-OmitInlinedMethodDebugLineInfo is also not passed by Quarkus, note that starting with Mandrel 23.1 / GraalVM for JDK 21 it's no longer needed, it's the default.