https://github.com/python/cpython/commit/152185fdf81515df55925e0bebccb9000c34cb11
commit: 152185fdf81515df55925e0bebccb9000c34cb11
branch: 3.15
author: Victor Stinner <[email protected]>
committer: vstinner <[email protected]>
date: 2026-10-13T13:32:16Z
summary:
[3.15] gh-158810: Fix Py_ARRAY_LENGTH() macro on C++ (#159315)
* gh-158810: Fix Py_ARRAY_LENGTH() macro on C++ (#158812)
(cherry picked from commit b2bfbce9a2cb00cb75c08230698cde408c130c92)
* gh-158810: Use _Py_TYPEOF in Py_ARRAY_LENGTH() (#158838)
Fix the compiler warning "extension used" when building test_cext
with clang.
* test_cext no longer overrides the CC environment variable if it's
already defined.
* test_cext now also logs __STRICT_ANSI__ macro.
(cherry picked from commit 85c03d47a240247d41799c2075f85f690558534c)
* Add Py_SETREF/XSETREF tests to test_cext
files:
A Misc/NEWS.d/next/C_API/2026-10-05-01-09-32.gh-issue-158810.F1p-PK.rst
M Include/pymacro.h
M Lib/test/test_cext/extension.c
M Lib/test/test_cext/setup.py
diff --git a/Include/pymacro.h b/Include/pymacro.h
index 7ecce44a0d2a42..a823d5535665b2 100644
--- a/Include/pymacro.h
+++ b/Include/pymacro.h
@@ -174,23 +174,27 @@
} while(0)
#endif
-/* Get the number of elements in a visible array
-
- This does not work on pointers, or arrays declared as [], or function
- parameters. With correct compiler support, such usage will cause a build
- error (see Py_BUILD_ASSERT_EXPR).
-
- Written by Rusty Russell, public domain, http://ccodearchive.net/
-
- Requires at GCC 3.1+ */
-#if (defined(__GNUC__) && !defined(__STRICT_ANSI__) && \
- (((__GNUC__ == 3) && (__GNUC_MINOR__ >= 1)) || (__GNUC__ >= 4)))
-/* Two gcc extensions.
- &a[0] degrades to a pointer: a different type from an array */
+// Get the number of elements in a visible array.
+//
+// This does not work on pointers, or arrays declared as [], or function
+// parameters. With correct compiler support, such usage will cause a build
+// error (see Py_BUILD_ASSERT_EXPR).
+//
+// Written by Rusty Russell, public domain, http://ccodearchive.net/
+//
+// Require GCC 4 (it works on GCC 3.1).
+//
+// Two GCC extensions: &a[0] degrades to a pointer, a different type from an
+// array.
+//
+// gh-158810: Do not use __builtin_types_compatible_p() in strict C ANSI mode
+// and on C++.
+#if (defined(__GNUC__) && __GNUC__ >= 4 && defined(_Py_TYPEOF) \
+ && !defined(__STRICT_ANSI__) && !defined(__cplusplus))
#define Py_ARRAY_LENGTH(array) \
(sizeof(array) / sizeof((array)[0]) \
- + Py_BUILD_ASSERT_EXPR(!__builtin_types_compatible_p(typeof(array), \
-
typeof(&(array)[0]))))
+ + Py_BUILD_ASSERT_EXPR(!__builtin_types_compatible_p(_Py_TYPEOF(array), \
+
_Py_TYPEOF(&(array)[0]))))
#else
#define Py_ARRAY_LENGTH(array) \
(sizeof(array) / sizeof((array)[0]))
diff --git a/Lib/test/test_cext/extension.c b/Lib/test/test_cext/extension.c
index e13f0c7911866b..dd2895520f751d 100644
--- a/Lib/test/test_cext/extension.c
+++ b/Lib/test/test_cext/extension.c
@@ -82,6 +82,8 @@ static PyObject *
test_macros(PyObject *Py_UNUSED(module), PyObject *Py_UNUSED(args))
{
PyObject *obj, *dict;
+ PyObject *slots[1];
+ int small_array[] = {2, 5, 7};
// test Py_BUILD_ASSERT() and Py_BUILD_ASSERT_EXPR()
Py_BUILD_ASSERT(sizeof(int) == sizeof(unsigned int));
@@ -97,17 +99,32 @@ test_macros(PyObject *Py_UNUSED(module), PyObject
*Py_UNUSED(args))
Py_CLEAR(obj);
assert(obj == _Py_NULL);
+ // gh-157649: Test Py_CLEAR() on an array
+ slots[0] = Py_None;
+ Py_CLEAR(slots[0]);
+ assert(slots[0] == _Py_NULL);
+
#ifndef Py_LIMITED_API
// Test Py_SETREF(): use typeof()/__typeof__() if available, or memcpy()
obj = Py_None;
Py_SETREF(obj, _Py_NULL);
assert(obj == _Py_NULL);
+ // gh-157649: Test Py_SETREF() on an array
+ slots[0] = Py_None;
+ Py_SETREF(slots[0], _Py_NULL);
+ assert(slots[0] == _Py_NULL);
+
// Test Py_XSETREF(): use typeof()/__typeof__() if available, or memcpy()
obj = Py_None;
Py_XSETREF(obj, _Py_NULL);
assert(obj == _Py_NULL);
-#endif
+
+ // gh-157649: Test Py_XSETREF() on an array
+ slots[0] = Py_None;
+ Py_XSETREF(slots[0], _Py_NULL);
+ assert(slots[0] == _Py_NULL);
+#endif // !Py_LIMITED_API
// Test that Py_BEGIN_CRITICAL_SECTION is available
dict = PyDict_New();
@@ -118,6 +135,9 @@ test_macros(PyObject *Py_UNUSED(module), PyObject
*Py_UNUSED(args))
Py_END_CRITICAL_SECTION();
Py_DECREF(dict);
+ // Test Py_ARRAY_LENGTH()
+ assert(Py_ARRAY_LENGTH(small_array) == 3);
+
Py_RETURN_NONE;
}
diff --git a/Lib/test/test_cext/setup.py b/Lib/test/test_cext/setup.py
index 2ef48261eadd1a..10a3887931932a 100644
--- a/Lib/test/test_cext/setup.py
+++ b/Lib/test/test_cext/setup.py
@@ -155,7 +155,7 @@ def main():
# option emits a C++ compiler warning. Remove "-std11" option from the
# CC command.
cmd = (sysconfig.get_config_var('CC') or '')
- if cmd is not None:
+ if cmd is not None and 'CC' not in os.environ:
if support.MS_WINDOWS:
std_prefix = '/std'
else:
diff --git
a/Misc/NEWS.d/next/C_API/2026-10-05-01-09-32.gh-issue-158810.F1p-PK.rst
b/Misc/NEWS.d/next/C_API/2026-10-05-01-09-32.gh-issue-158810.F1p-PK.rst
new file mode 100644
index 00000000000000..8d0878fd057a04
--- /dev/null
+++ b/Misc/NEWS.d/next/C_API/2026-10-05-01-09-32.gh-issue-158810.F1p-PK.rst
@@ -0,0 +1,2 @@
+Fix :c:macro:`Py_ARRAY_LENGTH()` macro on C++: do not use
+``__builtin_types_compatible_p()`` on C++. Patch by Victor Stinner.
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