MAINT: Pre-emptively handle the case when elsize == 0

Fixes np.fromiter and np.dtype. Neither of these code paths can currently be hit.

2 files changed, 15 insertions, 5 deletions

diff --git a/numpy/core/src/multiarray/ctors.c b/numpy/core/src/multiarray/ctors.c
index fb913d288..7958c619f 100644
--- a/numpy/core/src/multiarray/ctors.c
+++ b/numpy/core/src/multiarray/ctors.c
@@ -3708,14 +3708,15 @@ PyArray_FromIter(PyObject *obj, PyArray_Descr *dtype, npy_intp count)
     for (i = 0; (i < count || count == -1) &&
              (value = PyIter_Next(iter)); i++) {
         if (i >= elcount) {
+            npy_intp nbytes;
             /*
               Grow PyArray_DATA(ret):
               this is similar for the strategy for PyListObject, but we use
               50% overallocation => 0, 4, 8, 14, 23, 36, 56, 86 ...
             */
             elcount = (i >> 1) + (i < 4 ? 4 : 2) + i;
-            if (elcount <= NPY_MAX_INTP/elsize) {
-                new_data = PyDataMem_RENEW(PyArray_DATA(ret), elcount * elsize);
+            if (!npy_mul_with_overflow_intp(&nbytes, elcount, elsize)) {
+                new_data = PyDataMem_RENEW(PyArray_DATA(ret), nbytes);
             }
             else {
                 new_data = NULL;
diff --git a/numpy/core/src/multiarray/descriptor.c b/numpy/core/src/multiarray/descriptor.c
index 1ae6e34a6..608b5aa84 100644
--- a/numpy/core/src/multiarray/descriptor.c
+++ b/numpy/core/src/multiarray/descriptor.c
@@ -15,6 +15,7 @@
 
 #include "_datetime.h"
 #include "common.h"
+#include "templ_common.h" /* for npy_mul_with_overflow_intp */
 #include "descriptor.h"
 #include "alloc.h"
 
@@ -304,7 +305,8 @@ _convert_from_tuple(PyObject *obj)
         PyArray_Dims shape = {NULL, -1};
         PyArray_Descr *newdescr;
         npy_intp items;
-        int i;
+        int i, overflowed;
+        int nbytes;
 
         if (!(PyArray_IntpConverter(val, &shape)) || (shape.len > NPY_MAXDIMS)) {
             npy_free_cache_dim_obj(shape);
@@ -348,14 +350,21 @@ _convert_from_tuple(PyObject *obj)
             }
         }
         items = PyArray_OverflowMultiplyList(shape.ptr, shape.len);
-        if ((items < 0) || (items > (NPY_MAX_INT / type->elsize))) {
+        if (items < 0 || items > NPY_MAX_INT) {
+            overflowed = 1;
+        }
+        else {
+            overflowed = npy_mul_with_overflow_int(
+                &nbytes, type->elsize, (int) items);
+        }
+        if (overflowed) {
             PyErr_SetString(PyExc_ValueError,
                             "invalid shape in fixed-type tuple: dtype size in "
                             "bytes must fit into a C int.");
             npy_free_cache_dim_obj(shape);
             goto fail;
         }
-        newdescr->elsize = type->elsize * items;
+        newdescr->elsize = nbytes;
         if (newdescr->elsize == -1) {
             npy_free_cache_dim_obj(shape);
             goto fail;