cvFindContours Stack Overflow after cvAdaptiveThreshold about javacv HOT 6 CLOSED

The cause of this problem is most likely the same as the one for issue #10 
http://code.google.com/p/javacv/issues/detail?id=10 .. will keep you posted for 
something to try

Hi Samuel,

Thanks for your response. I tried adding setAutoSynch(false) to all CvSeq 
constructors, but that didn't actually fix the issue. To be certain, the error 
no longer appears, but the contours found, if at all, are 1-2 pixel radius 
circles randomly. Using your test2.java example, none of the contours found 
with the non-modified javacv.jar are found.

I'm mildly stumped, but would like to show you the exact error, on the off 
chance I didn't explain myself correctly:


Exception in thread "main" java.lang.StackOverflowError
    at com.sun.jna.Native.getNativeSize(Native.java:951)
    at com.sun.jna.Native.getNativeSize(Native.java:937)
    at com.sun.jna.Structure.getNativeAlignment(Structure.java:890)
    at com.sun.jna.Structure.calculateSize(Structure.java:823)
    at com.sun.jna.Structure.allocateMemory(Structure.java:282)
    at com.sun.jna.Structure.<init>(Structure.java:177)
    at com.sun.jna.Structure.<init>(Structure.java:167)
    at com.sun.jna.Structure.<init>(Structure.java:163)
    at com.sun.jna.Structure.<init>(Structure.java:154)
    at name.audet.samuel.javacv.jna.cxcore$CvArr.<init>(cxcore.java:2379)
    at name.audet.samuel.javacv.jna.cxcore$CvSeq.<init>(cxcore.java:3060)
    at name.audet.samuel.javacv.jna.cxcore$CvSeq$ByReference.<init>(cxcore.java:3092)
    at sun.reflect.GeneratedConstructorAccessor3.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at java.lang.Class.newInstance0(Unknown Source)
    at java.lang.Class.newInstance(Unknown Source)
    at com.sun.jna.Structure.newInstance(Structure.java:1159)
    at com.sun.jna.Structure.updateStructureByReference(Structure.java:486)
    at com.sun.jna.Pointer.getValue(Pointer.java:400)
    at com.sun.jna.Structure.readField(Structure.java:517)
    at com.sun.jna.Structure.read(Structure.java:419)
    at com.sun.jna.Structure.autoRead(Structure.java:1368)


loops the following infinitely:


    at com.sun.jna.Structure.updateStructureByReference(Structure.java:490)
    at com.sun.jna.Pointer.getValue(Pointer.java:400)
    at com.sun.jna.Structure.readField(Structure.java:517)
    at com.sun.jna.Structure.read(Structure.java:419)
    at com.sun.jna.Structure.autoRead(Structure.java:1368)


Thank you,
Nick

Once "auto-synch" is disabled, you need to use the readField() method to read 
the native values of the fields in the Structure. The values of the Java fields 
will not be correct.. Did you use readField() in your Java code? 

BTW, I modified CvSeq slightly in this test package to include a static 
autoSynch flag:
    http://www.ok.ctrl.titech.ac.jp/~saudet/javacv.jar
With that, something like the following should disable the default auto-synch 
behavior of any newly constructed CvSeq objects:
    CvSeq.autoSynch = false;
If that works, I plan to add the flag to all Structure in the next release... 
thanks

Hi Samuel,

Thanks for the advice. I'm not very familiar with JNA. Is there any way you 
could clarify on readField(). Am I to just replace read() with readField() in 
the cvSeq constructors?

Thank you,
Nick

For each individual field, yes.. if you have a field "int number", then instead 
of something like 
    int n = someStructure.number
you replace that with 
    int n = (Integer)someStructure.readField("number")

Marking this long-standing issue as fixed, since it should work. If you still 
get stack overflows after setting CvSeq.autoSynch = false, please reopen the 
issue. Otherwise please mark it as /verified/, thank you.