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rust-cpython: mark all PyLeaked methods as unsafe...
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.
Gregory Szorc - - Load All Authors

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error_private.h
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/ contrib / python-zstandard / zstd / common / error_private.h
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/*
* Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under both the BSD-style license (found in the
* LICENSE file in the root directory of this source tree) and the GPLv2 (found
* in the COPYING file in the root directory of this source tree).
* You may select, at your option, one of the above-listed licenses.
*/
/* Note : this module is expected to remain private, do not expose it */
#ifndef ERROR_H_MODULE
#define ERROR_H_MODULE
#if defined (__cplusplus)
extern "C" {
#endif
/* ****************************************
* Dependencies
******************************************/
#include <stddef.h> /* size_t */
#include "zstd_errors.h" /* enum list */
/* ****************************************
* Compiler-specific
******************************************/
#if defined(__GNUC__)
# define ERR_STATIC static __attribute__((unused))
#elif defined (__cplusplus) || (defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) /* C99 */)
# define ERR_STATIC static inline
#elif defined(_MSC_VER)
# define ERR_STATIC static __inline
#else
# define ERR_STATIC static /* this version may generate warnings for unused static functions; disable the relevant warning */
#endif
/*-****************************************
* Customization (error_public.h)
******************************************/
typedef ZSTD_ErrorCode ERR_enum;
#define PREFIX(name) ZSTD_error_##name
/*-****************************************
* Error codes handling
******************************************/
#undef ERROR /* reported already defined on VS 2015 (Rich Geldreich) */
#define ERROR(name) ZSTD_ERROR(name)
#define ZSTD_ERROR(name) ((size_t)-PREFIX(name))
ERR_STATIC unsigned ERR_isError(size_t code) { return (code > ERROR(maxCode)); }
ERR_STATIC ERR_enum ERR_getErrorCode(size_t code) { if (!ERR_isError(code)) return (ERR_enum)0; return (ERR_enum) (0-code); }
/*-****************************************
* Error Strings
******************************************/
const char* ERR_getErrorString(ERR_enum code); /* error_private.c */
ERR_STATIC const char* ERR_getErrorName(size_t code)
{
return ERR_getErrorString(ERR_getErrorCode(code));
}
#if defined (__cplusplus)
}
#endif
#endif /* ERROR_H_MODULE */