launchwrapper and minecraft 1.5.2 forge incompatability

[AZ-1282]

ASM 4.1 first breaks the launchwrapper and ASM 9.9 breaks Forge for minecraft 1.5.2
if i switch them in the order in the json file forge will refuse to launch

Expected behavior
is there a way to switch libraries after launch, maybe this isn't important because you could launch inside an ide, still reporting it though

logs
-- if ASM 4.1 is before ASM 9.9 --
Changing language to en_US
Using main class: org.mcphackers.launchwrapper.Launch
Launch arguments: C:\Program Files\Zulu\zulu-8\jre\bin\java, -Djava.library.path=C:\Users\AZiz\Desktop\mcp.\libraries\natives, -Dminecraft.launcher.brand=RetroMCP, -Dminecraft.launcher.version=v1.2, -cp, C:\Users\AZiz\Desktop\mcp.\libraries\org\ow2\asm\asm-all\4.1\asm-all-4.1.jar;C:\Users\AZiz\Desktop\mcp.\libraries\org\ow2\asm\asm\9.9\asm-9.9.jar;C:\Users\AZiz\Desktop\mcp.\libraries\org\ow2\asm\asm-tree\9.9\asm-tree-9.9.jar;C:\Users\AZiz\Desktop\mcp.\libraries\org\ow2\asm\asm-commons\9.9\asm-commons-9.9.jar;C:\Users\AZiz\Desktop\mcp.\libraries\net\java\jinput\jinput\2.0.5\jinput-2.0.5.jar;C:\Users\AZiz\Desktop\mcp.\libraries\net\java\jutils\jutils\1.0.0\jutils-1.0.0.jar;C:\Users\AZiz\Desktop\mcp.\libraries\org\lwjgl\lwjgl\lwjgl\2.9.4-nightly-20150209\lwjgl-2.9.4-nightly-20150209.jar;C:\Users\AZiz\Desktop\mcp.\libraries\org\lwjgl\lwjgl\lwjgl_util\2.9.4-nightly-20150209\lwjgl_util-2.9.4-nightly-20150209.jar;C:\Users\AZiz\Desktop\mcp.\libraries\org\lwjgl\lwjgl\lwjgl-platform\2.9.4-nightly-20150209\lwjgl-platform-2.9.4-nightly-20150209.jar;C:\Users\AZiz\Desktop\mcp.\libraries\com\paulscode\codecjorbis\20230120\codecjorbis-20230120.jar;C:\Users\AZiz\Desktop\mcp.\libraries\com\paulscode\codecwav\20101023\codecwav-20101023.jar;C:\Users\AZiz\Desktop\mcp.\libraries\com\paulscode\libraryjavasound\20101123\libraryjavasound-20101123.jar;C:\Users\AZiz\Desktop\mcp.\libraries\com\paulscode\librarylwjglopenal\20100824\librarylwjglopenal-20100824.jar;C:\Users\AZiz\Desktop\mcp.\libraries\com\paulscode\soundsystem\20120107\soundsystem-20120107.jar;C:\Users\AZiz\Desktop\mcp.\libraries\org\mcphackers\launchwrapper\1.2.4\launchwrapper-1.2.4.jar;C:\Users\AZiz\Desktop\mcp.\libraries\org\json\json\20230311\json-20230311.jar;C:\Users\AZiz\Desktop\mcp.\libraries\com\google\guava\guava\14.0-rc3\guava-14.0-rc3.jar;C:\Users\AZiz\Desktop\mcp.\libraries\net\sf\argo\argo\2.25\argo-2.25.jar;C:\Users\AZiz\Desktop\mcp.\libraries\org\bouncycastle\bcprov-jdk15on\1.48\bcprov-jdk15on-148.jar;C:\Users\AZiz\Desktop\mcp.\minecraft\bin;C:\Users\AZiz\Desktop\mcp.\minecraft\jars\deobfuscated.jar, -Xms1024M, -Xmx1024M, org.mcphackers.launchwrapper.Launch, --username, Player, --uuid, -, --session, -, --version, 1.5.2, --gameDir, ., --assetsDir, .\assets, --assetIndex, 1.4, --accessToken, -, --userProperties, {}, --userType, legacy, --versionType, snapshot, --skinProxy, pre-1.8,
Minecraft STDERR: Exception in thread "main" java.lang.ExceptionInInitializerError
Minecraft STDERR: at org.mcphackers.launchwrapper.Launch.getLoader(Launch.java:71)
Minecraft STDERR: at org.mcphackers.launchwrapper.Launch.launch(Launch.java:31)
Minecraft STDERR: at org.mcphackers.launchwrapper.Launch.main(Launch.java:27)
Minecraft STDERR: Caused by: java.lang.IllegalArgumentException
Minecraft STDERR: at org.objectweb.asm.ClassReader.(Unknown Source)
Minecraft STDERR: at org.objectweb.asm.ClassReader.(Unknown Source)
Minecraft STDERR: at org.objectweb.asm.ClassReader.(Unknown Source)
Minecraft STDERR: at org.mcphackers.launchwrapper.util.asm.NodeHelper.readClass(NodeHelper.java:90)
Minecraft STDERR: at org.mcphackers.launchwrapper.loader.LaunchClassLoader.getSystemClass(LaunchClassLoader.java:475)
Minecraft STDERR: at org.mcphackers.launchwrapper.loader.LaunchClassLoader.getSupportedClassVersion(LaunchClassLoader.java:483)
Minecraft STDERR: at org.mcphackers.launchwrapper.loader.LaunchClassLoader.(LaunchClassLoader.java:46)
Minecraft STDERR: ... 3 more

-- if ASM 9.9 is before ASM 4.1 --

Using main class: org.mcphackers.launchwrapper.Launch Launch arguments: C:\Program Files\Zulu\zulu-8\jre\bin\java, -Djava.library.path=C:\Users\AZiz\Desktop\mcp\.\libraries\natives, -Dminecraft.launcher.brand=RetroMCP, -Dminecraft.launcher.version=v1.2, -cp, C:\Users\AZiz\Desktop\mcp\.\libraries\org\ow2\asm\asm\9.9\asm-9.9.jar;C:\Users\AZiz\Desktop\mcp\.\libraries\org\ow2\asm\asm-tree\9.9\asm-tree-9.9.jar;C:\Users\AZiz\Desktop\mcp\.\libraries\org\ow2\asm\asm-commons\9.9\asm-commons-9.9.jar;C:\Users\AZiz\Desktop\mcp\.\libraries\net\java\jinput\jinput\2.0.5\jinput-2.0.5.jar;C:\Users\AZiz\Desktop\mcp\.\libraries\net\java\jutils\jutils\1.0.0\jutils-1.0.0.jar;C:\Users\AZiz\Desktop\mcp\.\libraries\org\lwjgl\lwjgl\lwjgl\2.9.4-nightly-20150209\lwjgl-2.9.4-nightly-20150209.jar;C:\Users\AZiz\Desktop\mcp\.\libraries\org\lwjgl\lwjgl\lwjgl_util\2.9.4-nightly-20150209\lwjgl_util-2.9.4-nightly-20150209.jar;C:\Users\AZiz\Desktop\mcp\.\libraries\org\lwjgl\lwjgl\lwjgl-platform\2.9.4-nightly-20150209\lwjgl-platform-2.9.4-nightly-20150209.jar;C:\Users\AZiz\Desktop\mcp\.\libraries\com\paulscode\codecjorbis\20230120\codecjorbis-20230120.jar;C:\Users\AZiz\Desktop\mcp\.\libraries\com\paulscode\codecwav\20101023\codecwav-20101023.jar;C:\Users\AZiz\Desktop\mcp\.\libraries\com\paulscode\libraryjavasound\20101123\libraryjavasound-20101123.jar;C:\Users\AZiz\Desktop\mcp\.\libraries\com\paulscode\librarylwjglopenal\20100824\librarylwjglopenal-20100824.jar;C:\Users\AZiz\Desktop\mcp\.\libraries\com\paulscode\soundsystem\20120107\soundsystem-20120107.jar;C:\Users\AZiz\Desktop\mcp\.\libraries\org\mcphackers\launchwrapper\1.2.4\launchwrapper-1.2.4.jar;C:\Users\AZiz\Desktop\mcp\.\libraries\org\json\json\20230311\json-20230311.jar;C:\Users\AZiz\Desktop\mcp\.\libraries\com\google\guava\guava\14.0-rc3\guava-14.0-rc3.jar;C:\Users\AZiz\Desktop\mcp\.\libraries\net\sf\argo\argo\2.25\argo-2.25.jar;C:\Users\AZiz\Desktop\mcp\.\libraries\org\bouncycastle\bcprov-jdk15on\1.48\bcprov-jdk15on-148.jar;C:\Users\AZiz\Desktop\mcp\.\libraries\org\ow2\asm\asm-all\4.1\asm-all-4.1.jar;C:\Users\AZiz\Desktop\mcp\.\minecraft\bin;C:\Users\AZiz\Desktop\mcp\.\minecraft\jars\deobfuscated.jar, -Xms1024M, -Xmx1024M, org.mcphackers.launchwrapper.Launch, --username, Player, --uuid, -, --session, -, --version, 1.5.2, --gameDir, ., --assetsDir, .\assets, --assetIndex, 1.4, --accessToken, -, --userProperties, {}, --userType, legacy, --versionType, snapshot, --skinProxy, pre-1.8, Minecraft STDERR: 2026-04-18 09:10:37 [INFO] [ForgeModLoader] Forge Mod Loader version 5.2.23.738 for Minecraft 1.5.2 loading Minecraft STDERR: 2026-04-18 09:10:37 [INFO] [ForgeModLoader] Java is OpenJDK 64-Bit Server VM, version 1.8.0_482, running on Windows 10:amd64:10.0, installed at C:\Program Files\Zulu\zulu-8\jre Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] java.lang.RuntimeException: java.lang.RuntimeException: java.lang.ClassNotFoundException: cpw.mods.fml.common.asm.FMLSanityChecker Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at cpw.mods.fml.relauncher.FMLRelauncher.setupHome(FMLRelauncher.java:192) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at cpw.mods.fml.relauncher.FMLRelauncher.relaunchApplet(FMLRelauncher.java:259) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at cpw.mods.fml.relauncher.FMLRelauncher.appletEntry(FMLRelauncher.java:229) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at net.minecraft.client.MinecraftApplet.init(MinecraftApplet.java:25) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at net.minecraft.client.Minecraft.main(Minecraft.java) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at java.lang.reflect.Method.invoke(Method.java:498) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at org.mcphackers.launchwrapper.loader.LaunchClassLoader.invokeMain(LaunchClassLoader.java:243) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at org.mcphackers.launchwrapper.target.MainLaunchTarget.launch(MainLaunchTarget.java:21) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at org.mcphackers.launchwrapper.Launch.launch(Launch.java:62) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at org.mcphackers.launchwrapper.Launch.main(Launch.java:27) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] Caused by: java.lang.RuntimeException: java.lang.ClassNotFoundException: cpw.mods.fml.common.asm.FMLSanityChecker Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at cpw.mods.fml.relauncher.RelaunchLibraryManager.handleLaunch(RelaunchLibraryManager.java:306) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at cpw.mods.fml.relauncher.FMLRelauncher.setupHome(FMLRelauncher.java:172) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] ... 12 more Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] Caused by: java.lang.ClassNotFoundException: cpw.mods.fml.common.asm.FMLSanityChecker Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at cpw.mods.fml.relauncher.RelaunchClassLoader.findClass(RelaunchClassLoader.java:238) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at java.lang.ClassLoader.loadClass(ClassLoader.java:419) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at java.lang.ClassLoader.loadClass(ClassLoader.java:352) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at java.lang.Class.forName0(Native Method) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at java.lang.Class.forName(Class.java:348) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at cpw.mods.fml.relauncher.RelaunchLibraryManager.handleLaunch(RelaunchLibraryManager.java:295) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] ... 13 more Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] Caused by: java.lang.UnsupportedOperationException: This feature requires ASM5 Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at org.objectweb.asm.MethodVisitor.visitParameter(MethodVisitor.java:123) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at org.objectweb.asm.ClassReader.readMethod(ClassReader.java:1388) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at org.objectweb.asm.ClassReader.accept(ClassReader.java:745) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at org.objectweb.asm.ClassReader.accept(ClassReader.java:425) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at cpw.mods.fml.common.asm.transformers.DeobfuscationTransformer.transform(DeobfuscationTransformer.java:38) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at cpw.mods.fml.relauncher.RelaunchClassLoader.runTransformers(RelaunchClassLoader.java:352) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] at cpw.mods.fml.relauncher.RelaunchClassLoader.findClass(RelaunchClassLoader.java:225) Minecraft STDERR: 2026-04-18 09:11:01 [INFO] [STDERR] ... 18 more

RetroMCP Version
v1.2

Minecraft version
1.5.2
Additional context
Obviously forge for 1.5.2

[PhoenixVX]

The issue here is that you're using too new of a Java version for the ASM version you are using. You can switch to Java 8 and ASM 4.1 will work as it should.

Switched this to a discussion as this is not an issue with RetroMCP itself.

[PhoenixVX]

Or more specifically, you are compiling and running the game with different JVM versions. The class files are compiled with something newer than Java 8 but it is attempting to parse them with an outdated ASM version.