CODEWITHSUNDEEP
javacstructjava-native-interfacejna
maxammann
maxammann

Reputation: 1048

JNA structure creation causes trouble

Heyho,

I have some kine of weird problem. I created a c library which contains the definition of a struct:

typedef struct rgb_ rgb;

struct rgb_ {
    uint8_t r;
    uint8_t g;
    uint8_t b;
};

Definition of the struct: https://github.com/p000ison/rgb-lm/blob/master/src/lm/led-matrix.h#L12

On the java side I'm calling the libraries' functions:

    LmLibrary.lmFontLibrary library = lm.lm_fonts_init();
    LmLibrary.lmFont font = lm.lm_fonts_font_new(library, ... font ..., 20);

    for (int x = 0; x < 32; x++) {
        for (int y = 0; y < 32; y++) {
            new rgb_.ByValue();  //<-------- Important line
            lm.lm_matrix_set_pixel(matrix, (short) x, (short) y, RED);

        }
    }

    lm.lm_fonts_print_string(library, matrix, "test", font, (short) 0, (short) 2, RED);
    lm.lm_fonts_font_free(library, font);

(https://github.com/p000ison/rgb-lm/blob/master/java/src/main/java/lm/Main.java#L35)

When calling with the "Important line" my programm get's a SIGSEGV at some "random" point. By removing that line it works just fine.

It's no problem of the c library as the test c programm runs fine:

lmFontLibrary *library = lm_fonts_init();

lmFont *font = lm_fonts_font_new(library, "/usr/share/fonts/truetype/msttcorefonts/arial.ttf", 20);


for (x = 0; x < 32; ++x) {
    for (y = 0; y < 32; ++y) {
        rgb blue = {0, 0, 255};
        lm_matrix_set_pixel(matrix, x, y, blue);
    };
}

lm_fonts_print_string(library, matrix, "Fuck", font, 0, 2, color);

(https://github.com/p000ison/rgb-lm/blob/master/examples/simple_pixels.c)

The functions which get called: https://github.com/p000ison/rgb-lm/blob/master/src/lm/font.c

EDIT: I figured out which line caused my library to crash: https://github.com/p000ison/rgb-lm/blob/master/src/lm/font.c#L97 I think this is random and has nothing to do with the font library.

EDIT: Running JNA 4.1.0

Upvotes: 0

Views: 88

Answers (1)

maxammann
maxammann

Reputation: 1048

So after tying a new more things which always lead to some kind of memory corruption I tried to use the jna version distributed by my linux distribution. The provided version was 3.2.7 by the libjna-java debian package.

After installing the packet and running my java programm with it everything workes great.

Not a bit c pro, but it seems like JNA overwrote some parts of my heap.

Some more information about the test envirnoment:

  • Platform: Linux pi 3.12.35+ #730 PREEMPT Fri Dec 19 18:31:24 GMT 2014 armv6l GNU/Linux
  • Hardware: Rapsberry PI B
  • JNA 4.1.0 which failed with SIGSEGV

JVM crash: http://pastebin.com/dFFx4abC

Upvotes: 1

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