Strange backtrace - where is the error?

Question

I'm developing an image processing application in C++. I've seen a lot of compiler errors and backtraces, but this one is new to me.

#0  0xb80c5430 in __kernel_vsyscall ()
#1  0xb7d1b6d0 in raise () from /lib/tls/i686/cmov/libc.so.6
#2  0xb7d1d098 in abort () from /lib/tls/i686/cmov/libc.so.6
#3  0xb7d5924d in ?? () from /lib/tls/i686/cmov/libc.so.6
#4  0xb7d62276 in ?? () from /lib/tls/i686/cmov/libc.so.6
#5  0xb7d639c5 in malloc () from /lib/tls/i686/cmov/libc.so.6
#6  0xb7f42f47 in operator new () from /usr/lib/libstdc++.so.6
#7  0x0805bd20 in Image<Color>::fft (this=0xb467640) at ../image_processing/image.cpp:545

What's happening here? The operator new is crashing, ok. But why? That's not an out of memory (it tries to allocate about 128Kb, a 128x64 pixel with two floats each). Also, it doesn't seam as it's an error in my own code (the constructor doesn't get touched!).

The code in the mentioned line (#7) is:

Image<Complex> *result = new Image<Complex>(this->resX, resY); 
// this->resX = 128, resY = 64 (both int), Complex is a typedef for std::complex<float>

Almost the same instantiation works on other places in my code. If I comment out this part of the code, it will crash a bit later on a similar part. I don't understand it, I also don't have any ideas, how to debug it. Any help?

Compiler is gcc 4.3.3, libc is 2.9 (both from Ubuntu Jaunty)

Update:

I've included the following lines just above the faulty line in the same method and in main()

    Image<Complex> *test = new Image<Complex>(128, 64);
    delete test;

The strange thing: in the same method it will crash, in main() it won't. As I mentioned, Complex is a typedef of std::complex<float>. The constructor doesn't get called, I've inserted a cout just before this line and in the constructor itself.

Update 2:

Thanks to KPexEA for this tip! I tried this:

Image<Complex> *test = new Image<Complex>(128, 64);
delete test;

kiss_fft_cpx *output = (kiss_fft_cpx*) malloc( this->resX * this->resY/2 * sizeof(kiss_fft_cpx) );
kiss_fftndr( cfg, input, output );

Image<Complex> *test2 = new Image<Complex>(128, 64);
delete test2;

It crashes at - you guess? - test2! So the malloc for my kissfft seams to be the faulty one. I'll take a look at it.

Final update:

Ok, it's done! Thanks to all of you!

Actually, I should have noticed it before. Last week, I noticed, that kissfft (a fast fourier transform library) made a 130x64 pixel fft image from a 128x128 pixel source image. Yes, 130 pixel broad, not 128. Don't ask me why, I don't know! So, 130x64x2xsizeof(float) bytes had to be allocated, not 128x64x... as I thought before. Strange, that it didn't crash just after I fixed that bug, but some days later.

For the record, my final code is:

int resY = (int) ceil(this->resY/2);

kiss_fft_cpx *output = (kiss_fft_cpx*) malloc( (this->resX+2) * resY * sizeof(kiss_fft_cpx) );
kiss_fftndr( cfg, input, output );

Image<Complex> *result = new Image<Complex>(this->resX, resY);

Thanks!

craesh

Answer 1

Perhaps a previously allocated chunk of memory has a buffer overflow that is corrupting the heap?

Answer 2

You are not allocating enough memory. The half-spectrum format of kissfft (and FFTW and IMKL for that matter) contains X*(Y/2+1) complex elements.

See the kiss_fftndr.h header file:

/* input timedata has dims[0] X dims[1] X ... X dims[ndims-1] scalar points

output freqdata has dims[0] X dims[1] X ... X dims[ndims-1]/2+1 complex points *