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rust-cpython: mark all PyLeaked methods as unsafe
Unfortunately, these methods can be abused to obtain the inner 'static
reference. The simplest (pseudo-code) example is:
let leaked: PyLeaked<&'static _> = shared.leak_immutable();
let static_ref: &'static _ = &*leaked.try_borrow(py)?;
// PyLeakedRef::deref() tries to bound the lifetime to itself, but
// the underlying data is a &'static reference, so the returned
// reference can be &'static.
This problem can be easily fixed by coercing the lifetime, but there are
many other ways to achieve that, and there wouldn't be a generic solution:
let leaked: PyLeaked<&'static [_]> = shared.leak_immutable();
let leaked_iter: PyLeaked<slice::Iter<'static, _>>
= unsafe { leaked.map(|v| v.iter()) };
let static_slice: &'static [_] = leaked_iter.try_borrow(py)?.as_slice();
So basically I failed to design the safe borrowing interface. Maybe we'll
instead have to add much more restricted interface on top of the unsafe
PyLeaked methods? For instance, Iterator::next() could be implemented if
its Item type is not &'a (where 'a may be cheated.)
Anyway, this seems not an easy issue, so it's probably better to leave the
current interface as unsafe, and get broader comments while upstreaming this
feature.
author | Yuya Nishihara <yuya@tcha.org> |
---|---|
date | Tue, 22 Oct 2019 16:04:34 +0900 |
parents | 1aee2ab0f902 |
children |
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#!/bin/sh # # This is an example of using HGEDITOR to create of diff to review the # changes while committing. # If you want to pass your favourite editor some other parameters # only for Mercurial, modify this: case "${EDITOR}" in "") EDITOR="vi" ;; emacs) EDITOR="$EDITOR -nw" ;; gvim|vim) EDITOR="$EDITOR -f -o" ;; esac HGTMP="" cleanup_exit() { rm -rf "$HGTMP" } # Remove temporary files even if we get interrupted trap "cleanup_exit" 0 # normal exit trap "exit 255" HUP INT QUIT ABRT TERM HGTMP=$(mktemp -d ${TMPDIR-/tmp}/hgeditor.XXXXXX) [ x$HGTMP != x -a -d $HGTMP ] || { echo "Could not create temporary directory! Exiting." 1>&2 exit 1 } ( grep '^HG: changed' "$1" | cut -b 13- | while read changed; do "$HG" diff "$changed" >> "$HGTMP/diff" done ) cat "$1" > "$HGTMP/msg" MD5=$(which md5sum 2>/dev/null) || \ MD5=$(which md5 2>/dev/null) [ -x "${MD5}" ] && CHECKSUM=`${MD5} "$HGTMP/msg"` if [ -s "$HGTMP/diff" ]; then $EDITOR "$HGTMP/msg" "$HGTMP/diff" || exit $? else $EDITOR "$HGTMP/msg" || exit $? fi [ -x "${MD5}" ] && (echo "$CHECKSUM" | ${MD5} -c >/dev/null 2>&1 && exit 13) mv "$HGTMP/msg" "$1" exit $?