(*free)(void *);
        } SecretDataAllocatorFuncs;

        NPY_NO_EXPORT void *
        shift_alloc(void *ctx, size_t sz) {
            SecretDataAllocatorFuncs *funcs = (SecretDataAllocatorFuncs *)ctx;
            char *real = (char *)funcs->malloc(sz + 64);
            if (real == NULL) {
                return NULL;
            }
            snprintf(real, 64, "originally allocated %ld", (unsigned long)sz);
            return (void *)(real + 64);
        }
        NPY_NO_EXPORT void *
        shift_zero(void *ctx, size_t sz, size_t cnt) {
            SecretDataAllocatorFuncs *funcs = (SecretDataAllocatorFuncs *)ctx;
            char *real = (char *)funcs->calloc(sz + 64, cnt);
            if (real == NULL) {
                return NULL;
            }
            snprintf(real, 64, "originally allocated %ld via zero",
                     (unsigned long)sz);
            return (void *)(real + 64);
        }
        NPY_NO_EXPORT void
        shift_free(void *ctx, void * p, npy_uintp sz) {
            SecretDataAllocatorFuncs *funcs = (SecretDataAllocatorFuncs *)ctx;
            if (p == NULL) {
                return ;
            }
            char *real = (char *)p - 64;
            if (strncmp(real, "originally allocated", 20) != 0) {
                fprintf(stdout, "uh-oh, unmatched shift_free, "
                        "no appropriate prefix\n");
                /* Make C runtime crash by calling free on the wrong address */
                funcs->free((char *)p + 10);
                /* funcs->free(real); */
            }
            else {
                npy_uintp i = (npy_uintp)atoi(real +20);
                if (i != sz) {
                    fprintf(stderr, "uh-oh, unmatched shift_free"
                            "(ptr, %ld) but allocated %ld\n", sz, i);
                    /* This happens in some places, only print */
                    funcs->free(real);
                }
                else {
                    funcs->free(real);
                }
            }
        }
        NPY_NO_EXPORT void *
        shift_realloc(void *ctx, void * p, npy_uintp sz) {
            SecretDataAllocatorFuncs *funcs = (SecretDataAllocatorFuncs *)ctx;
            if (p != NULL) {
                char *real = (char *)p - 64;
                if (strncmp(real, "originally allocated", 20) != 0) {
                    fprintf(stdout, "uh-oh, unmatched shift_realloc\n");
                    return realloc(p, sz);
                }
                return (void *)((char *)funcs->realloc(real, sz + 64) + 64);
            }
            else {
                char *real = (char *)funcs->realloc(p, sz + 64);
                if (real == NULL) {
                    return NULL;
                }
                snprintf(real, 64, "originally allocated "
                         "%ld  via realloc", (unsigned long)sz);
                return (void *)(real + 64);
            }
        }
        /* As an example, we use the standard {m|c|re}alloc/free funcs. */
        static SecretDataAllocatorFuncs secret_data_handler_ctx = {
            malloc,
            calloc,
            realloc,
            free
        };
        static PyDataMem_Handler secret_data_handler = {
            "secret_data_allocator",
            1,
            {
                &secret_data_handler_ctx, /* ctx */
                shift_alloc,              /* malloc */
                shift_zero,               /* calloc */
                shift_realloc,            /* realloc */
                shift_free                /* free */
            }
        };
        void warn_on_free(void *capsule) {
            PyErr_WarnEx(PyExc_UserWarning, "in warn_on_free", 1);
            void * obj = PyCapsule_GetPointer(capsule,
                                              PyCapsule_GetName(capsule));
            free(obj);
        };
        zimport_array();r