CODEWITHSUNDEEP
javalibgdxcrashjvmstack-trace
Matt Y
Matt Y

Reputation: 191

Getting line numbers from a stack trace in a JVM crash log

I'm trying to fix what appears to be a race condition in some code using libGDX. This particular race condition crashes the JVM when it happens.

Searching through the JVM crash log, I found the following lines:

Java frames: (J=compiled Java code, j=interpreted, Vv=VM code)
J 1128  com.badlogic.gdx.utils.BufferUtils.copyJni([FLjava/nio/Buffer;II)V (0 bytes) @ 0x0000000002d477b0 [0x0000000002d47740+0x70]
J 1365 C2 com.badlogic.gdx.graphics.g2d.SpriteBatch.flush()V (185 bytes) @ 0x0000000002e16ad4 [0x0000000002e16940+0x194]
J 1201 C1 com.badlogic.gdx.graphics.g2d.SpriteBatch.end()V (90 bytes) @ 0x0000000002d8f2d4 [0x0000000002d8f1c0+0x114]
J 1422 C1 com.me.mygame.screens.IslandScreen.render(F)V (848 bytes) @ 0x0000000002e40624 [0x0000000002e3a4e0+0x6144]
J 1539 C1 com.badlogic.gdx.Game.render()V (25 bytes) @ 0x0000000002e6c1dc [0x0000000002e6c000+0x1dc]
j  com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop()V+698
j  com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run()V+27
v  ~StubRoutines::call_stub

One particular line involves some of my own code:

J 1422 C1 com.me.mygame.screens.IslandScreen.render(F)V (848 bytes) @ 0x0000000002e40624 [0x0000000002e3a4e0+0x6144]

Is there any way I can find what the specific line that is causing this is? If not, what can be done to debug this crash?

Upvotes: 0

Views: 930

Answers (1)

apangin
apangin

Reputation: 98640

A stack trace in a crash log may contain both interpreted and compiled Java methods.

Interpreted methods (denoted by a small j) will also include the bytecode index (bci), e.g.

j com.me.mygame.screens.IslandScreen.render(F)V+727
                                                ^^^

Here the method render was executing the bytecode at position 727. To match this to a line number use Java decompiler like javap:

javap -c -verbose -cp CLASSPATH com.me.mygame.screens.IslandScreen

Look for LineNumberTable that maps lines in the source code to bytecode indices:

  LineNumberTable:
    line 7: 0
    line 8: 11
    ...
    line 66: 707
    line 67: 719   <-- find the nearest bci
    line 68: 731

You need the line number with the bci closest to (but not exceeding) 727. In the above example it is line 67.

Alternatively you may request JVM to execute a command right before the crash. jstack will help to generate full thread dump including line numbers.

java -XX:OnError="jstack -F %p" ...

Here -F means 'forced' mode and %p is automatically replaced by JVM process ID.

Upvotes: 2

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