Question

I’m using Apple GCC 4.2.1 and I’ve stumbled upon a strange problem with the following code… I always get EXC_BAD_ACCESS exception when trying to initialize __m128 class member variable. Unfortunately the following simplified code works in a test application, but maybe you can still help me locate the root of this problem?

I fail to understand the reason behind EXC_BAD_ACCESS exception – __m128 type is not a pointer and all other MyClass members are initialized and accessed without any problems, there are no signs of stack / heap corruption, everything works if I use local variables and there are no problems under MSVC… Maybe something is wrong with alignment?

Please help!

class MyClass
{
    public:
    // lots of members
    __m128 vect;

    MyClass()
    {
        vect = _mm_setr_ps (0.f, 0.f, 0.f, 10.0f); // Program received signal: “EXC_BAD_ACCESS”.
    }

    void iniialize()
    {
        __m128 localVector = _mm_setr_ps (0.f, 0.f, 0.f, 10.0f); // No problems
        vect = localVector; // Program received signal: “EXC_BAD_ACCESS”.
    }
};

Answer 1

From the top of my mind: i’d say alignment issues

Especially, the part where it says ‘lot’s of members’

Look at __attribute__ aligned

• Are stack variables aligned by the GCC __attribute__((aligned(x)))?
• http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Variable-Attributes.html#Variable-Attributes