gh-142419: Add mmap.set_name method for user custom annotation #142480

corona10 · 2025-12-09T17:32:19Z

Issue: Expose annotation to anonymous virtual memory ranges to mmap module #142419

📚 Documentation preview 📚: https://cpython-previews--142480.org.readthedocs.build/

Doc/library/mmap.rst

picnixz · 2025-12-10T08:47:43Z

Modules/mmapmodule.c

+    }
+#else
+    /* naming not supported on this platform */
+    PyErr_SetString(PyExc_ValueError,


In ssl.c we usually raise a NotImplementedError in such cases. If you always want to raise the same error, I suggest that you document this ValueError.

Modules/mmapmodule.c

Doc/library/mmap.rst

Doc/whatsnew/3.15.rst

picnixz · 2025-12-10T08:55:13Z

Lib/test/test_mmap.py

+        result = m.set_name(long_name)
+        self.assertIsNone(result)
+
+        # Test name too long


Can you add a test with NUL bytes inside it?

picnixz · 2025-12-10T08:55:59Z

Modules/mmapmodule.c

+mmap_mmap_set_name_impl(mmap_object *self, const char *name)
+/*[clinic end generated code: output=1edaf4fd51277760 input=6c7dd91cad205f07]*/
+{
+    const char* prefix = "cpython:mmap:";


Suggested change

const char* prefix = "cpython:mmap:";

const char *prefix = "cpython:mmap:";

Alternatively you can use a macro and in the printf have MACRO "%s" as a format string instead. Same idea as usages of PRI* macros

Modules/mmapmodule.c

Lib/test/test_mmap.py

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

corona10 · 2025-12-10T17:55:23Z

@picnixz @vstinner PTAL :)

Lib/test/test_mmap.py

Misc/NEWS.d/next/Library/2025-12-10-02-31-43.gh-issue-142419.C8_LES.rst

Doc/library/mmap.rst

picnixz · 2025-12-11T15:05:11Z

Modules/mmapmodule.c

+                    "Annotation of mmap is not supported on this platform");
+    return NULL;
+#endif
+    Py_RETURN_NONE;


You can move this one in the ifdef block.

Co-authored-by: Victor Stinner <vstinner@python.org>

vstinner · 2025-12-12T12:31:12Z

Doc/library/mmap.rst


+   .. method:: set_name(name, /)
+
+      Annotate the memory map with the given *name* for easier identification


Suggested change

Annotate the memory map with the given *name* for easier identification

Annotate the memory mapping with the given *name* for easier identification

vstinner · 2025-12-12T12:31:43Z

Doc/library/mmap.rst

+      to Python or if Python is built in :ref:`debug mode <debug-build>`
+      The length of *name* must not exceed 67 bytes.
+
+      .. availability:: Linux >= 5.17


Suggested change

.. availability:: Linux >= 5.17

.. availability:: Linux >= 5.17 (kernel built with `CONFIG_ANON_VMA_NAME` option)

vstinner · 2025-12-12T12:32:03Z

Doc/whatsnew/3.15.rst

  (Contributed by Serhiy Storchaka in :gh:`78502`.)

+* Added the :meth:`mmap.mmap.set_name` method
+  to annotate an anonymous memory map


Suggested change

to annotate an anonymous memory map

to annotate an anonymous memory mapping

vstinner · 2025-12-12T12:32:43Z

Lib/test/test_mmap.py

+        self.assertIsNone(result)
+
+        # Test name too long
+        too_long_name = 'x' * 80


Suggested change

too_long_name = 'x' * 80

too_long_name = 'x' * 68

vstinner · 2025-12-12T12:33:40Z

Modules/mmapmodule.c

+        return NULL;
+    }
+    if (self->flags & MAP_ANONYMOUS) {
+        char buf[81] = {0, };


I don't think that it's useful to initialize the buffer since we are directly writing into it.

Suggested change

char buf[81] = {0, };

char buf[81];

vstinner · 2025-12-12T12:35:23Z

Modules/mmapmodule.c

+/*[clinic end generated code: output=1edaf4fd51277760 input=6c7dd91cad205f07]*/
+{
+#if defined(MAP_ANONYMOUS) && defined(__linux__)
+    const char *prefix = "cpython:mmap:";


Is it really needed to include mmap: in the name? Why not just:

Suggested change

const char *prefix = "cpython:mmap:";

const char *prefix = "cpython:";

An alternative is to even omit the prefix, and just the name to name.

vstinner · 2025-12-12T12:36:08Z

Lib/test/test_mmap.py

+
+        # Test name length limit (80 chars including prefix "cpython:mmap:")
+        # Prefix is 13 chars, so max name is 67 chars
+        long_name = 'x' * 30


I suggest to test the longest valid name here:

Suggested change

long_name = 'x' * 30

long_name = 'x' * 67

And check for overflow below (68 characters).

corona10 added 7 commits December 10, 2025 01:32

pythongh-142419: Add mmap.set_name method for annotation

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corona10 requested a review from AA-Turner as a code owner December 9, 2025 17:32

corona10 requested review from vstinner and removed request for AA-Turner December 9, 2025 17:32

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Expose annotation to anonymous virtual memory ranges to mmap module #142419

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Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

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no-issue: Fix _requires_unix_version if platform.system() is not matched #142596

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corona10 added 2 commits December 12, 2025 04:15

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	const char* prefix = "cpython:mmap:";
	const char *prefix = "cpython:mmap:";


		.. method:: set_name(name, /)

		Annotate the memory map with the given name for easier identification

	Annotate the memory map with the given name for easier identification
	Annotate the memory mapping with the given name for easier identification

	.. availability:: Linux >= 5.17
	.. availability:: Linux >= 5.17 (kernel built with `CONFIG_ANON_VMA_NAME` option)

	to annotate an anonymous memory map
	to annotate an anonymous memory mapping

	const char *prefix = "cpython:mmap:";
	const char *prefix = "cpython:";

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gh-142419: Add mmap.set_name method for user custom annotation #142480

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