MAINT: Avoid malloc(0) in string (and generic) sorting

2 files changed, 7 insertions, 0 deletions

diff --git a/numpy/core/src/npysort/heapsort.cpp b/numpy/core/src/npysort/heapsort.cpp
index 3956de51f..77a4bda74 100644
--- a/numpy/core/src/npysort/heapsort.cpp
+++ b/numpy/core/src/npysort/heapsort.cpp
@@ -55,6 +55,9 @@ npy_heapsort(void *start, npy_intp num, void *varr)
     PyArrayObject *arr = (PyArrayObject *)varr;
     npy_intp elsize = PyArray_ITEMSIZE(arr);
     PyArray_CompareFunc *cmp = PyArray_DESCR(arr)->f->compare;
+    if (elsize == 0) {
+        return 0;  /* no need for sorting elements of no size */
+    }
     char *tmp = (char *)malloc(elsize);
     char *a = (char *)start - elsize;
     npy_intp i, j, l;
diff --git a/numpy/core/src/npysort/npysort_heapsort.h b/numpy/core/src/npysort/npysort_heapsort.h
index 442320094..16750b817 100644
--- a/numpy/core/src/npysort/npysort_heapsort.h
+++ b/numpy/core/src/npysort/npysort_heapsort.h
@@ -128,6 +128,10 @@ int string_heapsort_(type *start, npy_intp n, void *varr)
 {
     PyArrayObject *arr = (PyArrayObject *)varr;
     size_t len = PyArray_ITEMSIZE(arr) / sizeof(type);
+    if (len == 0) {
+        return 0;  /* no need for sorting if strings are empty */
+    }
+
     type *tmp = (type *)malloc(PyArray_ITEMSIZE(arr));
     type *a = (type *)start - len;
     npy_intp i, j, l;