Description

serhiy-storchaka

opened on Aug 27, 2025

Issue body actions

Bug report

On Posix platforms without mremap() (FreeBSD, OpenBSD, NetBSD, OpenIndiana) mmap.resize() raises SystemError.

SystemError: mmap: resizing not available--no mremap()

SystemError should only be raised in case of the misuse of the C API or breaking internal consistency of the Python core. It is one step away from a segmentation fault or undefined behavior. If some function cannot be implemented, it should either do not exist (causing AttributeError) or raise more appropriate exception when called, like NotImplemenedError, or OSError(ENOTSUP), or simply RuntimeError.

Linked PRs

• gh-138205: Remove the resize method on mmap object on platforms don't support it #138276
• gh-138205: explicit mention to mmap.mmap.resize in "Porting to Python 3.15" notes #143440

Activity

1. serhiy-storchaka

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   3.13only security fixesonly security fixes

   3.14bugs and security fixesbugs and security fixes

   3.15bugs and security fixesbugs and security fixes

   on Aug 27, 2025
2. YvesDup commented on Aug 27, 2025

   

   YvesDup

   on Aug 27, 2025

   Contributor

   More actions

   This also happens on MacOSX 15.1, M4 pro
3. serhiy-storchaka commented on Aug 28, 2025

   

   serhiy-storchaka

   on Aug 28, 2025

   MemberAuthor

   More actions

   There was other improper use of SystemError in the mmap module: #7381.
4. aisk commented on Aug 31, 2025

   

   aisk

   on Aug 31, 2025

   Member

   More actions

   I'd like to just remove the method on platforms which doesn't support it for consistent reasons, just like the madvise method is not exist on platforms which doesn't support it.
5. kumaraditya303

   added a commit that references this issue on Sep 6, 2025

   gh-138205: Remove the `resize` method on `mmap` object on platforms d…

   c919d02
6. serhiy-storchaka

   removed

   3.13only security fixesonly security fixes

   3.14bugs and security fixesbugs and security fixes

   on Sep 6, 2025
7. serhiy-storchaka commented on Sep 6, 2025

   

   serhiy-storchaka

   on Sep 6, 2025

   MemberAuthor

   More actions

   Since this is a very old behavior, it is not worth to backport the change.
8. serhiy-storchaka

   closed this as completedon Sep 6, 2025
9. lkollar

   added a commit that references this issue on Sep 9, 2025

   pythongh-138205: Remove the `resize` method on `mmap` object on platf…

   5da862a
10. picnixz

    added a commit that references this issue on Jan 5, 2026

    gh-138205: explicit mention to `mmap.mmap.resize` in "Porting to Pyth…

    1569275
11. thunder-coding

    added a commit that references this issue on Feb 15, 2026

    pythongh-138205: explicit mention to `mmap.mmap.resize` in "Porting t…

    d51742e

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