python
diff --git a/‎Misc/NEWS.d/next/Windows/2024-04-24-05-16-32.gh-issue-118209.Ryyzlz.rst
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+2-1Lines changed: 2 additions & 1 deletion b/‎Misc/NEWS.d/next/Windows/2024-04-24-05-16-32.gh-issue-118209.Ryyzlz.rst
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+2-1Lines changed: 2 additions & 1 deletion
diff --git a/‎Modules/mmapmodule.c
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+9-5Lines changed: 9 additions & 5 deletions b/‎Modules/mmapmodule.c
Copy file name to clipboardExpand all lines: Modules/mmapmodule.c
+9-5Lines changed: 9 additions & 5 deletions
@@ -1 +1,2 @@
-Fix crashes in :func:`mmap.read`, :func:`mmap.read_byte` and :func:`mmap.write` on Windows when the underlying file operation raises errors.
+Fix crashes in :func:`mmap.read`, :func:`mmap.read_byte`, :func:`mmap.write`
+and :func:`mmap.write_byte` on Windows when the underlying file operation raises errors.
@@ -511,14 +511,18 @@ mmap_write_byte_method(mmap_object *self,
         return NULL;
 
     CHECK_VALID(NULL);
-    if (self->pos < self->size) {
-        self->data[self->pos++] = value;
-        Py_RETURN_NONE;
-    }
-    else {
+    if (self->pos >= self->size) {
         PyErr_SetString(PyExc_ValueError, "write byte out of range");
         return NULL;
     }
+
+    if (safe_memcpy(self->data + self->pos, value, 1) < 0) {
+        return NULL;
+    }
+    else {
+        self->pos++;
+        Py_RETURN_NONE;
+    }
 }
 
 static PyObject *