mmap.resize() can raise SystemError

[serhiy-storchaka]

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

[YvesDup]

This also happens on MacOSX 15.1, M4 pro

[serhiy-storchaka]

There was other improper use of SystemError in the mmap module: #7381.

[aisk]

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.

[serhiy-storchaka]

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