1. The Unstable Book
  2. Compiler environment variables
    1. RUSTC_BOOTSTRAP
    2. RUSTC_OVERRIDE_VERSION_STRING
  3. Compiler flags
    1. allow_features
    2. autodiff
    3. branch_protection
    4. cf_protection
    5. codegen_backend
    6. codegen_options
    7. control_flow_guard
    8. coverage_options
    9. crate_attr
    10. debug_info_for_profiling
    11. debug_info_type_line_numbers
    12. default_visibility
    13. direct_access_external_data
    14. dump_mono_stats
    15. dump_mono_stats_format
    16. dylib_lto
    17. eagerly_emit_delayed_bugs
    18. embed_metadata
    19. embed_source
    20. emit_stack_sizes
    21. emscripten_wasm_eh
    22. env_set
    23. export_executable_symbols
    24. extern_options
    25. external_clangrt
    26. fixed_x18
    27. fmt_debug
    28. function_return
    29. hint_mostly_unused
    30. instrument_xray
    31. link_native_libraries
    32. lint_llvm_ir
    33. llvm_module_flag
    34. location_detail
    35. macro_stats
    36. min_function_alignment
    37. move_size_limit
    38. no_jump_tables
    39. no_parallel_llvm
    40. no_steal_thir
    41. no_unique_section_names
    42. on_broken_pipe
    43. patchable_function_entry
    44. print_check_cfg
    45. print_crate_root_lint_levels
    46. print_supported_crate_types
    47. profile_sample_use
    48. randomize_layout
    49. reg_struct_return
    50. regparm
    51. remap_cwd_prefix
    52. remap_path_scope
    53. report_time
    54. sanitizer
    55. self_profile
    56. self_profile_events
    57. shell_argfiles
    58. small_data_threshold
    59. src_hash_algorithm
    60. temps_dir
    61. tiny_const_eval_limit
    62. tls_model
    63. track_diagnostics
    64. treat_err_as_bug
    65. ub_checks
    66. unsound_mir_opts
    67. verbose_asm
    68. virtual_function_elimination
    69. wasm_c_abi
  4. Language features
    1. aarch64_unstable_target_feature
    2. aarch64_ver_target_feature
    3. abi_avr_interrupt
    4. abi_cmse_nonsecure_call
    5. abi_custom
    6. abi_gpu_kernel
    7. abi_msp430_interrupt
    8. abi_ptx
    9. abi_riscv_interrupt
    10. abi_unadjusted
    11. abi_vectorcall
    12. abi_x86_interrupt
    13. adt_const_params
    14. alloc_error_handler
    15. allocator_internals
    16. allow_internal_unsafe
    17. allow_internal_unstable
    18. anonymous_lifetime_in_impl_trait
    19. apx_target_feature
    20. arbitrary_self_types
    21. arbitrary_self_types_pointers
    22. arm_target_feature
    23. asm_cfg
    24. asm_experimental_arch
    25. asm_experimental_reg
    26. asm_goto_with_outputs
    27. asm_unwind
    28. associated_const_equality
    29. associated_type_defaults
    30. async_drop
    31. async_fn_in_dyn_trait
    32. async_fn_track_caller
    33. async_for_loop
    34. async_trait_bounds
    35. auto_traits
    36. avx10_target_feature
    37. box_patterns
    38. bpf_target_feature
    39. builtin_syntax
    40. c_variadic
    41. cfg_contract_checks
    42. cfg_emscripten_wasm_eh
    43. cfg_overflow_checks
    44. cfg_relocation_model
    45. cfg_sanitize
    46. cfg_sanitizer_cfi
    47. cfg_target_compact
    48. cfg_target_has_atomic
    49. cfg_target_has_atomic_equal_alignment
    50. cfg_target_has_reliable_f16_f128
    51. cfg_target_thread_local
    52. cfg_ub_checks
    53. cfg_version
    54. cfi_encoding
    55. closure_lifetime_binder
    56. closure_track_caller
    57. cmse_nonsecure_entry
    58. compiler_builtins
    59. const_async_blocks
    60. const_closures
    61. const_destruct
    62. const_for
    63. const_precise_live_drops
    64. const_trait_impl
    65. const_try
    66. contracts
    67. contracts_internals
    68. coroutine_clone
    69. coroutines
    70. coverage_attribute
    71. csky_target_feature
    72. custom_inner_attributes
    73. custom_mir
    74. custom_test_frameworks
    75. decl_macro
    76. default_field_values
    77. deprecated_safe
    78. deprecated_suggestion
    79. deref_patterns
    80. doc_auto_cfg
    81. doc_cfg
    82. doc_cfg_hide
    83. doc_masked
    84. doc_notable_trait
    85. dropck_eyepatch
    86. ergonomic_clones
    87. ermsb_target_feature
    88. exhaustive_patterns
    89. explicit_extern_abis
    90. explicit_tail_calls
    91. export_stable
    92. extended_varargs_abi_support
    93. extern_system_varargs
    94. extern_types
    95. f128
    96. f16
    97. ffi_const
    98. ffi_pure
    99. fmt_debug
    100. fn_align
    101. fn_delegation
    102. freeze_impls
    103. frontmatter
    104. fundamental
    105. gen_blocks
    106. generic_assert
    107. generic_const_exprs
    108. generic_const_items
    109. generic_const_parameter_types
    110. generic_pattern_types
    111. global_registration
    112. guard_patterns
    113. half_open_range_patterns_in_slices
    114. hexagon_target_feature
    115. if_let_guard
    116. impl_trait_in_assoc_type
    117. impl_trait_in_bindings
    118. impl_trait_in_fn_trait_return
    119. import_trait_associated_functions
    120. inherent_associated_types
    121. intra_doc_pointers
    122. intrinsics
    123. lahfsahf_target_feature
    124. lang_items
    125. large_assignments
    126. lazy_type_alias
    127. link_arg_attribute
    128. link_cfg
    129. link_llvm_intrinsics
    130. linkage
    131. loongarch_target_feature
    132. loop_match
    133. m68k_target_feature
    134. macro_metavar_expr
    135. macro_metavar_expr_concat
    136. marker_trait_attr
    137. min_generic_const_args
    138. min_specialization
    139. mips_target_feature
    140. more_maybe_bounds
    141. more_qualified_paths
    142. movrs_target_feature
    143. multiple_supertrait_upcastable
    144. must_not_suspend
    145. mut_ref
    146. naked_functions_rustic_abi
    147. naked_functions_target_feature
    148. native_link_modifiers_as_needed
    149. needs_panic_runtime
    150. negative_bounds
    151. negative_impls
    152. never_patterns
    153. never_type
    154. never_type_fallback
    155. new_range
    156. no_core
    157. no_sanitize
    158. non_exhaustive_omitted_patterns_lint
    159. non_lifetime_binders
    160. offset_of_enum
    161. offset_of_slice
    162. omit_gdb_pretty_printer_section
    163. optimize_attribute
    164. panic_runtime
    165. patchable_function_entry
    166. pattern_complexity_limit
    167. pattern_types
    168. pin_ergonomics
    169. postfix_match
    170. powerpc_target_feature
    171. prelude_import
    172. prfchw_target_feature
    173. proc_macro_hygiene
    174. profiler_runtime
    175. raw_dylib_elf
    176. ref_pat_eat_one_layer_2024
    177. ref_pat_eat_one_layer_2024_structural
    178. register_tool
    179. repr_simd
    180. return_type_notation
    181. riscv_target_feature
    182. rtm_target_feature
    183. rust_cold_cc
    184. rustc_allow_const_fn_unstable
    185. rustc_attrs
    186. rustc_private
    187. rustdoc_internals
    188. rustdoc_missing_doc_code_examples
    189. s390x_target_feature
    190. simd_ffi
    191. sized_hierarchy
    192. sparc_target_feature
    193. specialization
    194. sse4a_target_feature
    195. staged_api
    196. stmt_expr_attributes
    197. strict_provenance_lints
    198. string_deref_patterns
    199. structural_match
    200. super_let
    201. supertrait_item_shadowing
    202. tbm_target_feature
    203. test_unstable_lint
    204. thread_local
    205. trait_alias
    206. transmute_generic_consts
    207. transparent_unions
    208. trivial_bounds
    209. try_blocks
    210. type_alias_impl_trait
    211. type_changing_struct_update
    212. unboxed_closures
    213. unqualified_local_imports
    214. unsafe_binders
    215. unsafe_fields
    216. unsized_const_params
    217. unsized_fn_params
    218. used_with_arg
    219. wasm_target_feature
    220. where_clause_attrs
    221. with_negative_coherence
    222. x86_amx_intrinsics
    223. x87_target_feature
    224. xop_target_feature
    225. yeet_expr
    226. yield_expr
  5. Library Features
    1. abort_unwind
    2. acceptfilter
    3. addr_parse_ascii
    4. align_to_uninit_mut
    5. alloc_error_hook
    6. alloc_internals
    7. alloc_layout_extra
    8. allocator_api
    9. alloctests
    10. arc_is_unique
    11. array_chunks
    12. array_into_iter_constructors
    13. array_ptr_get
    14. array_repeat
    15. array_try_from_fn
    16. array_try_map
    17. array_windows
    18. as_array_of_cells
    19. ascii_char
    20. ascii_char_variants
    21. assert_matches
    22. async_fn_traits
    23. async_gen_internals
    24. async_iter_from_iter
    25. async_iterator
    26. atomic_from_mut
    27. atomic_internals
    28. atomic_try_update
    29. autodiff
    30. backtrace_frames
    31. bigint_helper_methods
    32. bikeshed_guaranteed_no_drop
    33. binary_heap_drain_sorted
    34. binary_heap_into_iter_sorted
    35. binary_heap_peek_mut_refresh
    36. bool_to_result
    37. bound_as_ref
    38. box_as_ptr
    39. box_into_boxed_slice
    40. box_into_inner
    41. box_vec_non_null
    42. breakpoint
    43. bstr
    44. bstr_internals
    45. btree_cursors
    46. btree_entry_insert
    47. btree_extract_if
    48. btree_set_entry
    49. btreemap_alloc
    50. buf_read_has_data_left
    51. bufreader_peek
    52. c_size_t
    53. c_void_variant
    54. can_vector
    55. cell_leak
    56. cfg_accessible
    57. cfg_eval
    58. cfg_select
    59. char_internals
    60. char_max_len
    61. clone_to_uninit
    62. cmp_minmax
    63. coerce_pointee_validated
    64. coerce_unsized
    65. cold_path
    66. concat_bytes
    67. const_alloc_error
    68. const_array_each_ref
    69. const_btree_len
    70. const_carrying_mul_add
    71. const_clone
    72. const_cmp
    73. const_default
    74. const_deref
    75. const_eval_select
    76. const_float_round_methods
    77. const_format_args
    78. const_from
    79. const_heap
    80. const_index
    81. const_ops
    82. const_pathbuf_osstring_new
    83. const_range_bounds
    84. const_raw_ptr_comparison
    85. const_ref_cell
    86. const_slice_from_mut_ptr_range
    87. const_slice_from_ptr_range
    88. const_slice_make_iter
    89. const_slice_reverse
    90. const_slice_rotate
    91. const_split_off_first_last
    92. const_type_id
    93. const_type_name
    94. container_error_extra
    95. context_ext
    96. control_flow_into_value
    97. convert_float_to_int
    98. core_float_math
    99. core_intrinsics
    100. core_intrinsics_fallbacks
    101. core_io_borrowed_buf
    102. core_private_bignum
    103. core_private_diy_float
    104. coroutine_trait
    105. cow_is_borrowed
    106. cstr_bytes
    107. cstr_display
    108. cstr_internals
    109. cursor_split
    110. deadline_api
    111. debug_closure_helpers
    112. dec2flt
    113. deref_pure_trait
    114. derive_clone_copy
    115. derive_coerce_pointee
    116. derive_const
    117. derive_eq
    118. dir_entry_ext2
    119. discriminant_kind
    120. disjoint_bitor
    121. dispatch_from_dyn
    122. downcast_unchecked
    123. drain_keep_rest
    124. duration_constants
    125. duration_constructors
    126. duration_constructors_lite
    127. duration_millis_float
    128. duration_units
    129. edition_panic
    130. error_generic_member_access
    131. error_iter
    132. error_reporter
    133. error_type_id
    134. exact_div
    135. exact_size_is_empty
    136. exclusive_wrapper
    137. exit_status_error
    138. exitcode_exit_method
    139. extend_one
    140. extend_one_unchecked
    141. fd
    142. fd_read
    143. file_buffered
    144. file_with_nul
    145. float_algebraic
    146. float_erf
    147. float_gamma
    148. float_minimum_maximum
    149. flt2dec
    150. fmt_helpers_for_derive
    151. fmt_internals
    152. fn_ptr_trait
    153. fn_traits
    154. forget_unsized
    155. format_args_nl
    156. formatting_options
    157. freeze
    158. future_join
    159. gen_future
    160. generic_assert_internals
    161. generic_atomic
    162. get_disjoint_mut_helpers
    163. get_mut_unchecked
    164. hash_set_entry
    165. hasher_prefixfree_extras
    166. hashmap_internals
    167. hint_must_use
    168. inplace_iteration
    169. int_format_into
    170. int_from_ascii
    171. int_roundings
    172. integer_atomics
    173. internal_impls_macro
    174. internal_output_capture
    175. io_const_error
    176. io_const_error_internals
    177. io_error_inprogress
    178. io_error_more
    179. io_error_uncategorized
    180. io_slice_as_bytes
    181. ip
    182. ip_as_octets
    183. ip_from
    184. is_ascii_octdigit
    185. is_loongarch_feature_detected
    186. is_riscv_feature_detected
    187. isolate_most_least_significant_one
    188. iter_advance_by
    189. iter_array_chunks
    190. iter_chain
    191. iter_collect_into
    192. iter_from_coroutine
    193. iter_intersperse
    194. iter_is_partitioned
    195. iter_macro
    196. iter_map_windows
    197. iter_next_chunk
    198. iter_order_by
    199. iter_partition_in_place
    200. iterator_try_collect
    201. iterator_try_reduce
    202. junction_point
    203. layout_for_ptr
    204. lazy_cell_into_inner
    205. lazy_get
    206. legacy_receiver_trait
    207. liballoc_internals
    208. libstd_sys_internals
    209. likely_unlikely
    210. linked_list_cursors
    211. linked_list_remove
    212. linked_list_retain
    213. linux_pidfd
    214. local_key_cell_update
    215. local_waker
    216. lock_value_accessors
    217. log_syntax
    218. map_try_insert
    219. mapped_lock_guards
    220. maybe_uninit_array_assume_init
    221. maybe_uninit_as_bytes
    222. maybe_uninit_fill
    223. maybe_uninit_slice
    224. maybe_uninit_uninit_array_transpose
    225. maybe_uninit_write_slice
    226. mem_copy_fn
    227. more_float_constants
    228. mpmc_channel
    229. mutex_data_ptr
    230. new_range_api
    231. new_zeroed_alloc
    232. next_index
    233. nonzero_bitwise
    234. nonzero_from_mut
    235. nonzero_internals
    236. nonzero_ops
    237. normalize_lexically
    238. numfmt
    239. once_cell_get_mut
    240. once_cell_try
    241. once_cell_try_insert
    242. one_sided_range
    243. option_array_transpose
    244. option_zip
    245. os_str_slice
    246. os_string_truncate
    247. panic_abort
    248. panic_always_abort
    249. panic_backtrace_config
    250. panic_can_unwind
    251. panic_internals
    252. panic_payload_as_str
    253. panic_unwind
    254. panic_update_hook
    255. partial_ord_chaining_methods
    256. path_add_extension
    257. path_file_prefix
    258. pattern
    259. pattern_type_macro
    260. pattern_type_range_trait
    261. peer_credentials_unix_socket
    262. phantom_variance_markers
    263. pin_coerce_unsized_trait
    264. pointer_is_aligned_to
    265. pointer_try_cast_aligned
    266. portable_simd
    267. prelude_future
    268. prelude_next
    269. print_internals
    270. proc_macro_def_site
    271. proc_macro_diagnostic
    272. proc_macro_expand
    273. proc_macro_internals
    274. proc_macro_quote
    275. proc_macro_span
    276. proc_macro_totokens
    277. proc_macro_tracked_env
    278. proc_macro_value
    279. process_chroot
    280. process_exitcode_internals
    281. process_internals
    282. process_setsid
    283. profiler_runtime_lib
    284. ptr_alignment_type
    285. ptr_as_ref_unchecked
    286. ptr_as_uninit
    287. ptr_internals
    288. ptr_mask
    289. ptr_metadata
    290. pub_crate_should_not_need_unstable_attr
    291. random
    292. range_bounds_is_empty
    293. range_into_bounds
    294. raw_os_error_ty
    295. raw_slice_split
    296. raw_vec_internals
    297. read_buf
    298. reentrant_lock
    299. reentrant_lock_data_ptr
    300. restricted_std
    301. result_option_map_or_default
    302. round_char_boundary
    303. rt
    304. rwlock_data_ptr
    305. rwlock_downgrade
    306. sealed
    307. seek_io_take_position
    308. seek_stream_len
    309. set_ptr_value
    310. setgroups
    311. sgx_platform
    312. sized_type_properties
    313. slice_as_array
    314. slice_concat_ext
    315. slice_concat_trait
    316. slice_from_ptr_range
    317. slice_index_methods
    318. slice_internals
    319. slice_iter_mut_as_mut_slice
    320. slice_partition_dedup
    321. slice_pattern
    322. slice_ptr_get
    323. slice_range
    324. slice_split_once
    325. slice_swap_unchecked
    326. solid_ext
    327. sort_floats
    328. split_array
    329. split_as_slice
    330. std_internals
    331. stdarch_arm_feature_detection
    332. stdarch_mips_feature_detection
    333. stdarch_powerpc_feature_detection
    334. stdarch_s390x_feature_detection
    335. stdio_makes_pipe
    336. step_trait
    337. str_as_str
    338. str_from_raw_parts
    339. str_from_utf16_endian
    340. str_internals
    341. str_lines_remainder
    342. str_split_inclusive_remainder
    343. str_split_remainder
    344. str_split_whitespace_remainder
    345. strict_overflow_ops
    346. strict_provenance_atomic_ptr
    347. string_from_utf8_lossy_owned
    348. string_into_chars
    349. string_remove_matches
    350. substr_range
    351. sync_poison_mod
    352. sync_unsafe_cell
    353. tcp_deferaccept
    354. tcp_linger
    355. tcplistener_into_incoming
    356. temporary_niche_types
    357. test
    358. thin_box
    359. thread_id_value
    360. thread_local_internals
    361. thread_raw
    362. thread_sleep_until
    363. thread_spawn_hook
    364. trace_macros
    365. track_path
    366. transmutability
    367. trim_prefix_suffix
    368. trusted_fused
    369. trusted_len
    370. trusted_len_next_unchecked
    371. trusted_random_access
    372. trusted_step
    373. try_find
    374. try_reserve_kind
    375. try_trait_v2
    376. try_trait_v2_residual
    377. try_trait_v2_yeet
    378. try_with_capacity
    379. tuple_trait
    380. type_ascription
    381. ub_checks
    382. uefi_std
    383. uint_bit_width
    384. unchecked_neg
    385. unchecked_shifts
    386. unicode_internals
    387. unique_rc_arc
    388. unix_file_vectored_at
    389. unix_mkfifo
    390. unix_send_signal
    391. unix_set_mark
    392. unix_socket_ancillary_data
    393. unix_socket_exclbind
    394. unix_socket_peek
    395. unsafe_cell_access
    396. unsafe_pinned
    397. unsigned_nonzero_div_ceil
    398. unsigned_signed_diff
    399. unsize
    400. unwrap_infallible
    401. update_panic_count
    402. utf16_extra
    403. variant_count
    404. vec_deque_iter_as_slices
    405. vec_deque_pop_if
    406. vec_deque_truncate_front
    407. vec_into_chunks
    408. vec_into_raw_parts
    409. vec_peek_mut
    410. vec_push_within_capacity
    411. vec_split_at_spare
    412. wasi_ext
    413. windows_by_handle
    414. windows_c
    415. windows_change_time
    416. windows_handle
    417. windows_net
    418. windows_process_exit_code_from
    419. windows_process_extensions_async_pipes
    420. windows_process_extensions_force_quotes
    421. windows_process_extensions_main_thread_handle
    422. windows_process_extensions_raw_attribute
    423. windows_process_extensions_show_window
    424. windows_process_extensions_startupinfo
    425. windows_stdio
    426. wrapping_int_impl
    427. wrapping_next_power_of_two
    428. write_all_vectored
    429. yeet_desugar_details