Always include <string.h>

Author: vstinner

Doc/c-api/intro.rst

@@ -123,6 +123,7 @@ System includes
    * ``<limits.h>``
    * ``<math.h>``
    * ``<stdarg.h>``
+   * ``<string.h>``
    * ``<wchar.h>``
    * ``<sys/types.h>`` (if present)
 
@@ -138,11 +139,6 @@ System includes
    * ``<errno.h>``
    * ``<stdio.h>``
    * ``<stdlib.h>``
-   * ``<string.h>``
-
-   The ``<string.h>`` header is also included when using :ref:`Limited API
-   <limited-c-api>` 3.11 or newer if Python is unable to get a ``typeof()``
-   implementation.
 
 .. note::
 

Include/Python.h

@@ -22,12 +22,13 @@
 #include <limits.h>               // INT_MAX
 #include <math.h>                 // HUGE_VAL
 #include <stdarg.h>               // va_list
+#include <string.h>               // memcpy()
 #include <wchar.h>                // wchar_t
 #ifdef HAVE_SYS_TYPES_H
 #  include <sys/types.h>          // ssize_t
 #endif
 
-// <errno.h>, <stdio.h>, <stdlib.h> and <string.h> headers are no longer used
+// <errno.h>, <stdio.h> and <stdlib.h> headers are no longer used
 // by Python, but kept for the backward compatibility of existing third party C
 // extensions. They are not included by limited C API version 3.11 and newer.
 //
@@ -37,7 +38,6 @@
 #  include <errno.h>              // errno
 #  include <stdio.h>              // FILE*
 #  include <stdlib.h>             // getenv()
-#  include <string.h>             // memcpy()
 #endif
 #if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 < 0x030d0000
 #  include <ctype.h>              // tolower()

Include/refcount.h

@@ -471,9 +471,6 @@ static inline Py_ALWAYS_INLINE void Py_DECREF(PyObject *op)
  * and so avoid type punning. Otherwise, use memcpy() which causes type erasure
  * and so prevents the compiler to reuse an old cached 'op' value after
  * Py_CLEAR().
- *
- * Include <string.h> if _Py_TYPEOF() is not available, since the limited C API
- * version 3.11 and newer doesn't include it.
  */
 #ifdef _Py_TYPEOF
 #define Py_CLEAR(op) \
@@ -486,7 +483,6 @@ static inline Py_ALWAYS_INLINE void Py_DECREF(PyObject *op)
         } \
     } while (0)
 #else
-#include <string.h>               // memcpy()
 #define Py_CLEAR(op) \
     do { \
         PyObject **_tmp_op_ptr = _Py_CAST(PyObject**, &(op)); \

Misc/NEWS.d/next/C_API/2026-02-10-14-49-49.gh-issue-121617.57vMqa.rst

@@ -1,3 +1,3 @@
-Fix the :c:macro:`Py_CLEAR` implementation in the limited C API version 3.11
-and newer: include ``<string.h>`` to get the ``memcpy()`` function. Patch by
-Victor Stinner.
+``Python.h`` now also includes ``<string.h>`` in the limited C API version 3.11
+and newer to fix the :c:macro:`Py_CLEAR` macro which uses ``memcpy()``. Patch
+by Victor Stinner.