2
votes

I have a piece of JNI code with a mem leak:

Detected memory leaks!
Dumping objects ->
{76} normal block at 0x277522F8, 52 bytes long.
 Data: < "u' "u' "u'    > F8 22 75 27 F8 22 75 27 F8 22 75 27 CD CD CD CD
Object dump complete.

So, I set a breakpoint ont the specified memory allocation number (76 in this case).

_crtBreakAlloc = 76;

But the application never stop execution like if that allocation was never performed.

I also took two memory snapshots at the beginnning and at the end of the program, and I compared them.

(At code beginning):

_CrtMemCheckpoint( &s1 );

(At code end):

_CrtMemCheckpoint( &s2 );

_CrtMemState s3;
_CrtMemDifference( &s3, &s1, &s2);
_CrtMemDumpStatistics( &s3 );

Here the result:

0 bytes in 0 Free Blocks.
0 bytes in 0 Normal Blocks.
0 bytes in 0 CRT Blocks.
0 bytes in 0 Ignore Blocks.
0 bytes in 0 Client Blocks.
Largest number used: 2839 bytes.
Total allocations: 101483 bytes.

It seems that all is OK.

I can't figure out what is happening. Is it a false positive mem leak? Or is a memleak of the JVM? If so, is there a way to detect it?

Added after the solution was found:

I modified the initialization of a static map and the problem has been solved. In particular, I transformed a private static member from map to map*. The problem is that when you initialize a static, it must be initialized with a constant. Here is how I changed the declaration of the static member:

static const map<wstring, enumValue>* mapParamNames;

So my initialize() method becomes:

map<wstring, paramNames>* m = new map<wstring, paramNames>();
(*m)[L"detectCaptions"] = detectCaptions;
(*m)[L"insertEmptyParagraphsForBigInterlines"] = insertEmptyParagraphsForBigInterlines;
(*m)[L"fastMode"] = fastMode;
(*m)[L"predefinedTextLanguage"] = predefinedTextLanguage;
(*m)[L"detectFontSize"] = detectFontSize;
(*m)[L"saveCharacterRecognitionVariants"] = saveCharacterRecognitionVariants;
(*m)[L"detectBold"] = detectBold;
(*m)[L"saveWordRecognitionVariants"] = saveWordRecognitionVariants;

KernelParamsSetter::mapParamNames = m;

Finally, I inserted the delete of the map in the class destructor:

delete KernelParamsSetter::mapParamNames;

Hope this can be useful for someone.

1
Not exactly what you are asking about, but I had success with an allocation hook stackoverflow.com/q/4154941/57428 in similar case. - sharptooth

1 Answers

2
votes

One possibility would be that memory allocation 76 occurs during the static initialization of a global variable. In that case, you may be setting _crtBreakAlloc too late to catch the allocation.