From 1f4cee005b4da19f2e2e20236e5eac7b4f59e21e Mon Sep 17 00:00:00 2001
From: Frotty <Frotty@users.noreply.github.com>
Date: Thu, 8 Oct 2026 14:58:50 +0200
Subject: [PATCH] Start the compiler with compact object headers

The compiler holds millions of small objects. The runtime of the distribution carries the base class
data sharing archive for compact object headers (wurstscript/WurstScript#1389), which a JVM uses only
in the header mode it runs with, so the compiler is started with the option.
---
 src/main/kotlin/global/InstallationManager.kt |  5 ++-
 src/test/kotlin/InstallationTests.kt          | 32 +++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/src/main/kotlin/global/InstallationManager.kt b/src/main/kotlin/global/InstallationManager.kt
index de7e9c9..0f2733f 100644
--- a/src/main/kotlin/global/InstallationManager.kt
+++ b/src/main/kotlin/global/InstallationManager.kt
@@ -24,6 +24,7 @@ object InstallationManager {
     private const val LANGUAGE_AGENT_DOC_ENTRY = "agent-docs/WURST_LANGUAGE.md"
     private const val GRILL_JAR_NAME = "grill.jar"
     private const val LEGACY_GRILL_JAR_NAME = "WurstSetup.jar"
+    private const val COMPACT_OBJECT_HEADERS = "-XX:+UseCompactObjectHeaders"
 
     val installDir: Path get() = configuredInstallDir()
     val compilerDir: Path get() = installDir.resolve("wurst-compiler")
@@ -193,7 +194,9 @@ object InstallationManager {
     fun compilerLaunchCommand(vararg extraArgs: String): Array<String> {
         val compiler = detectCompilerJar() ?: compilerJar
         val java = bundledJavaCommand()
-        return arrayOf(java, "-jar", compiler.toAbsolutePath().toString(), *extraArgs)
+        // The compiler holds millions of small objects, and the runtime of the distribution carries the base class
+        // data sharing archive for compact object headers, which a JVM uses only in the header mode it runs with.
+        return arrayOf(java, COMPACT_OBJECT_HEADERS, "-jar", compiler.toAbsolutePath().toString(), *extraArgs)
     }
 
     private fun bundledJavaCommand(): String {
diff --git a/src/test/kotlin/InstallationTests.kt b/src/test/kotlin/InstallationTests.kt
index f1412bb..04949d7 100644
--- a/src/test/kotlin/InstallationTests.kt
+++ b/src/test/kotlin/InstallationTests.kt
@@ -19,6 +19,38 @@ class InstallationTests {
 		assert(InstallationManager.status != InstallationManager.InstallationStatus.NOT_INSTALLED)
 	}
 
+	@Test(priority = 8)
+	fun testCompilerLaunchCommandUsesCompactObjectHeaders() {
+		val previousInstallDir = System.getProperty("wurst.install.dir")
+		val installDir = Files.createTempDirectory("wurst-setup-launch")
+		try {
+			System.setProperty("wurst.install.dir", installDir.toString())
+			Files.createDirectories(InstallationManager.compilerDir)
+			JarOutputStream(Files.newOutputStream(InstallationManager.compilerJar)).use { }
+			Files.createDirectories(InstallationManager.bundledJava.parent)
+			Files.writeString(InstallationManager.bundledJava, "")
+			InstallationManager.bundledJava.toFile().setExecutable(true)
+
+			// the compiler holds millions of small objects; the runtime of the distribution has the base archive for this mode
+			Assert.assertEquals(
+				InstallationManager.compilerLaunchCommand("-build").toList(),
+				listOf(
+					InstallationManager.bundledJava.toAbsolutePath().toString(),
+					"-XX:+UseCompactObjectHeaders",
+					"-jar",
+					InstallationManager.compilerJar.toAbsolutePath().toString(),
+					"-build"
+				)
+			)
+		} finally {
+			if (previousInstallDir == null) {
+				System.clearProperty("wurst.install.dir")
+			} else {
+				System.setProperty("wurst.install.dir", previousInstallDir)
+			}
+		}
+	}
+
 	@Test(priority = 8)
 	fun testCompilerWithoutAgentDocsRemovesStaleLanguageDoc() {
 		val previousInstallDir = System.getProperty("wurst.install.dir")