C++ OpenGL glTexImage2D Access Violation

Question

I'm writing an application using OpenGL (freeglut and glew).

I also wanted textures so I did some research on the Bitmap file format and wrote a struct for the main header and another for the DIB header (info header).

Then I started writing the loader. It automatically binds the texture to OpenGL. Here is the function:

static unsigned int ReadInteger(FILE *fp)
{
    int a, b, c, d;

    // Integer is 4 bytes long.
    a = getc(fp);  
    b = getc(fp);  
    c = getc(fp);  
    d = getc(fp);

    // Convert the 4 bytes to an integer.
    return ((unsigned int) a) + (((unsigned int) b) << 8) +
           (((unsigned int) c) << 16) + (((unsigned int) d) << 24);
}

static unsigned int ReadShort(FILE *fp)
{
    int a, b;

    // Short is 2 bytes long.
    a = getc(fp);  
    b = getc(fp);

    // Convert the 2 bytes to a short (int16).
    return ((unsigned int) a) + (((unsigned int) b) << 8);
}

    GLuint LoadBMP(const char* filename)
{
    FILE* file;

    // Check if a file name was provided.
    if (!filename)
        return 0;

    // Try to open file.
    fopen_s(&file, filename, "rb");

    // Return if the file could not be open.
    if (!file)
    {
        cout << "Warning: Could not find texture '" << filename << "'." << endl;
        return 0;
    }

    // Read signature.
    unsigned char signature[2];
    fread(&signature, 2, 1, file);

    // Use signature to identify a valid bitmap.
    if (signature[0] != BMPSignature[0] || signature[1] != BMPSignature[1])
    {
        fclose(file);
        return 0;
    }

    // Read width and height.
    unsigned long width, height;
    fseek(file, 16, SEEK_CUR); // After the signature we have 16bytes until the width.
    width = ReadInteger(file);
    height = ReadInteger(file);

    // Calculate data size (we'll only support 24bpp).
    unsigned long dataSize;
    dataSize = width * height * 3;

    // Make sure planes is 1.
    if (ReadShort(file) != 1)
    {
        cout << "Error: Could not load texture '" << filename << "' (planes is not 1)." << endl;
        return 0;
    }

    // Make sure bpp is 24.
    if (ReadShort(file) != 24)
    {
        cout << "Error: Could not load texture '" << filename << "' (bits per pixel is not 24)." << endl;
        return 0;
    }

    // Move pointer to beggining of data. (after the bpp we have 24 bytes until the data)
    fseek(file, 24, SEEK_CUR);

    // Allocate memory and read the image data.
    unsigned char* data = new unsigned char[dataSize];

    if (!data)
    {
        fclose(file);
        cout << "Warning: Could not allocate memory to store data of '" << filename << "'." << endl;
        return 0;
    }

    fread(data, dataSize, 1, file);

    if (data == NULL)
    {
        fclose(file);
        cout << "Warning: Could no load data from '" << filename << "'." << endl;
        return 0;
    }

    // Close the file.
    fclose(file);

    // Create the texture.
    GLuint texture;
    glGenTextures(1, &texture);
    glBindTexture(GL_TEXTURE_2D, texture);

    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR); //NEAREST);
    glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE); 

    gluBuild2DMipmaps(GL_TEXTURE_2D, GL_RGB, width, height, GL_BGR_EXT, GL_UNSIGNED_BYTE, data);

    return texture;
}

I know that the bitmap's data is correctly read because I outputted it's data to the console and compared with the image opened in paint.

The problem here is this line:

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, dibheader.width,
    dibheader.height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);

Most of the times I run the application this line crashes with the error:

Unhandled exception at 0x008ffee9 in GunsGL.exe: 0xC0000005: Access violation reading location 0x00af7002.

This is the Disassembly of where the error occurs:

movzx       ebx,byte ptr [esi+2]

It's not an error with my loader, because I've downloaded other loaders. A downloaded loader that I used was this one from NeHe.

EDIT: (CODE UPDATED ABOVE)

I rewrote the loader, but I still get the crash on the same line. Instead of that crash, sometimes I get a crash on mlock.c (same error message is I recall correctly):

void __cdecl _lock (
        int locknum
        )
{

        /*
         * Create/open the lock, if necessary
         */
        if ( _locktable[locknum].lock == NULL ) {

            if ( !_mtinitlocknum(locknum) )
                _amsg_exit( _RT_LOCK );
        }

        /*
         * Enter the critical section.
         */

        EnterCriticalSection( _locktable[locknum].lock );
}

On the line:

EnterCriticalSection( _locktable[locknum].lock );

Also, here is a screen shot of one of those times the applications doesn't crash (the texture is obviously not right): http://i.stack.imgur.com/4Mtso.jpg

Edit2:

Updated code with the new working one. (The reply marked as an answer does not contain all that was needed for this to work, but it was vital)

Answer 1

Try glPixelStorei(GL_UNPACK_ALIGNMENT, 1) before your glTexImage2D() call.