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POJava JNI - EXCEPTION_ACCESS_VIOLATION while returning jintArray
 

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  1. POJava JNI - EXCEPTION_ACCESS_VIOLATION while returning jintArray
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    <p>A really weird thing happens in this code</p> <pre><code> JNIEXPORT jintArray JNICALL Java_jsdr_SdrLibrary_getTunerGains (JNIEnv * env, jclass obj, jlong pointer) { rtlsdr_dev_t * dev; int * gains; jintArray ji; jint * buff; int i; int size; dev = (rtlsdr_dev_t *) pointer; size = rtlsdr_get_tuner_gains(dev, gains); if (size &lt;= 0) .. throws an error, irrelevant code .. buff = (jint *) malloc(size * sizeof(jint)); for (i = 0; i &lt; size; i++) buff[i] = gains[i]; ji = (*env)-&gt;NewIntArray(env, size); (*env)-&gt;SetIntArrayRegion(env, ji, 0, size, buff); return ji; } </code></pre> <p>The method actually returns a result that I can handle in Java with</p> <pre><code> System.out.println(printArray(SdrLibrary.getTunerGains(pointer))); </code></pre> <p>where printArray is just a simple</p> <pre><code>public static String printArray(int[] arr) { String buff = "["+arr[0]; for (int i = 1; i &lt; arr.length; i++) buff+=", "+arr[i]; return buff+"]"; } </code></pre> <p>The output is the following</p> <pre><code>[-10, 15, 40, 65, 90, 115, 140, 165, 190, 215, 240, 290, 340, 420, 430, 450, 470, 490] # # A fatal error has been detected by the Java Runtime Environment: # # EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x6d86c2ff, pid=7160, tid=5880 # # JRE version: 6.0_31-b05 # Java VM: Java HotSpot(TM) Client VM (20.6-b01 mixed mode, sharing windows-x86 ) # Problematic frame: # V [jvm.dll+0x7c2ff] # # An error report file with more information is saved as: # C:\Users\Marto\workspace\JSDR\hs_err_pid7160.log # # If you would like to submit a bug report, please visit: # http://java.sun.com/webapps/bugreport/crash.jsp # </code></pre> <p>As you can see it returns a result but immediately after that the JM crashes and no further lines get executed. I would definitely appreciate any help! Thank you!</p> <p><strong>EDIT:</strong> If I remove the call to rtlsdr_get_tuner_gains and instead initialize the gains array manually, no error is observed. Since this method is inside a dll, can I prevent it somehow from crashing the JNI?</p>
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    1. USMartin Marinov
    1. USMartin Marinov
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    1. COYou're passing a pointer disguised as a long? Really? I suspect some code you haven't shown here is corrupting memory. Apart from the fact that you're leaking `buff`, and you're not checking for errors on JNI calls, there's nothing obviously wrong in the code you have posted.
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      1. USAlan Stokes
    2. COAs for the long, I don't have a lot of choice. It needs to be stored somewhere... Do you have any better suggestions? Also, look at the edit, I have added a few observations. As for the leaking of buff, I had a delete(buff) but I thought this might be causing the problem but it isn't. It seems like it's coming from the library. That's quite weird.
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      1. POJava JNI - EXCEPTION_ACCESS_VIOLATION while returning jintArray
      1. USMartin Marinov
    3. COYour edit makes it sound even more like you have a bug elsewhere. You can prevent it from crashing by fixing the bug.
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      1. USFlexo
 

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