MSP Object instantiation crash

I'm working on an MSP object. I copied the project from a known-good Xcode project and I've compared it with the examples, but I keep getting obex errors when I try to load it into Max which, from what I've read, usually indicate that there's something amiss in the setup. The problem is that I'm getting this with a very straightforward setup.

I went through the Xcode project and swapped over everything that had the name of the old project in it, and I've cleaned, etc. Can anyone provide some insight?

Here's the relevant code:
#include "ext.h"
#include "ext_obex.h"
#include "z_dsp.h"

static t_class *foo_class;

typedef struct _foo {

    t_pxobject m_obj;
    // rest of the structure’s fields
} t_foo;

// Prototypes
t_int *foo_perform(t_int *w);
void foo_dsp(t_foo *x, t_signal **sp, short *count);
void *foo_new(void);
void foo_mode(t_foo *x, int mode);
void foo_assist(t_foo *x, void *b, long m, long a, char *s);
void foo_float(t_foo *x, double f);

int main(void)
{    

    // NEW METHOD
    t_class *c;

    c = class_new("foo~", (method)foo_new, (method)dsp_free, sizeof(t_foo), NULL, 0);

    class_dspinit(c);    // new style object version of dsp_initclass();    

    class_addmethod(c, (method)foo_dsp,"dsp", A_CANT, 0);
    class_addmethod(c, (method)foo_mode, "mode", A_LONG, 0);
    class_addmethod(c, (method)foo_float,        "float",    A_FLOAT, 0);
    class_addmethod(c, (method)foo_assist,    "assist",    A_CANT, 0);

    class_register(CLASS_BOX, c);    // register class as a box class
    foo_class = c;
    return 0;
}

void *foo_new(void) {
    t_foo *c = (t_foo *) object_alloc(foo_class);

    dsp_setup((t_pxobject *)c,3); // Three inlets: input, freq, res
    // Always crashes here...

// Create outlet
    outlet_new((t_object *)c, "signal");    // Create outlet

    //c->freq = 60.f;
    //c->res = 0.5;

    return (c);

}

t_int *foo_perform(t_int *w) {
return (w+6)
}

void foo_dsp(t_foo *x, t_signal **sp, short *count) {

    x->smprate = sp[0]->s_sr;
    x->vecSize = sp[0]->s_n;
    x->invsmp = 1./x->vecSize; //
    x->invSR = 1.f/sp[0]->s_sr;

    dsp_add(foo_perform, 5, sp[0]->s_vec, sp[1]->s_vec, sp[2]->s_vec, sp[3]->s_vec,x);
}

Here's the crash log:
0 com.cycling74.MaxMSP     0x000b7e0c class_obexoffset_get + 6
1 com.cycling74.MaxMSP     0x000b8b8f object_obex_get + 29
2 com.cycling74.MaxMSP     0x000b8beb object_obex_lookup + 39
3 com.cycling74.MaxAPI     0x00ebb9d2 object_obex_lookup + 45
4 com.cycling74.MaxAudioAPI     0x0e591677 z_dsp_setup + 68
5 com.apple.PM_foo_     0x0f7fbcd2 foo_new + 50