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. linker_features
    33. lint_llvm_ir
    34. llvm_module_flag
    35. location_detail
    36. macro_stats
    37. min_function_alignment
    38. move_size_limit
    39. no_jump_tables
    40. no_parallel_llvm
    41. no_steal_thir
    42. no_unique_section_names
    43. on_broken_pipe
    44. patchable_function_entry
    45. print_check_cfg
    46. print_crate_root_lint_levels
    47. print_supported_crate_types
    48. profile_sample_use
    49. randomize_layout
    50. reg_struct_return
    51. regparm
    52. remap_cwd_prefix
    53. remap_path_scope
    54. report_time
    55. sanitizer
    56. self_profile
    57. self_profile_events
    58. shell_argfiles
    59. small_data_threshold
    60. src_hash_algorithm
    61. temps_dir
    62. tiny_const_eval_limit
    63. tls_model
    64. track_diagnostics
    65. treat_err_as_bug
    66. ub_checks
    67. unsound_mir_opts
    68. verbose_asm
    69. virtual_function_elimination
    70. 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_heap
    79. const_ops
    80. const_pathbuf_osstring_new
    81. const_range_bounds
    82. const_raw_ptr_comparison
    83. const_ref_cell
    84. const_slice_from_mut_ptr_range
    85. const_slice_from_ptr_range
    86. const_slice_make_iter
    87. const_slice_reverse
    88. const_split_off_first_last
    89. const_type_id
    90. const_type_name
    91. container_error_extra
    92. context_ext
    93. control_flow_into_value
    94. convert_float_to_int
    95. core_float_math
    96. core_intrinsics
    97. core_intrinsics_fallbacks
    98. core_io_borrowed_buf
    99. core_private_bignum
    100. core_private_diy_float
    101. coroutine_trait
    102. cow_is_borrowed
    103. cstr_bytes
    104. cstr_display
    105. cstr_internals
    106. cursor_split
    107. deadline_api
    108. debug_closure_helpers
    109. dec2flt
    110. deref_pure_trait
    111. derive_clone_copy
    112. derive_coerce_pointee
    113. derive_const
    114. derive_eq
    115. dir_entry_ext2
    116. discriminant_kind
    117. disjoint_bitor
    118. dispatch_from_dyn
    119. downcast_unchecked
    120. drain_keep_rest
    121. duration_constants
    122. duration_constructors
    123. duration_constructors_lite
    124. duration_millis_float
    125. duration_units
    126. edition_panic
    127. error_generic_member_access
    128. error_iter
    129. error_reporter
    130. error_type_id
    131. exact_div
    132. exact_size_is_empty
    133. exclusive_wrapper
    134. exit_status_error
    135. exitcode_exit_method
    136. extend_one
    137. extend_one_unchecked
    138. fd
    139. fd_read
    140. file_buffered
    141. file_with_nul
    142. float_algebraic
    143. float_erf
    144. float_gamma
    145. float_minimum_maximum
    146. flt2dec
    147. fmt_helpers_for_derive
    148. fmt_internals
    149. fn_ptr_trait
    150. fn_traits
    151. forget_unsized
    152. format_args_nl
    153. formatting_options
    154. freeze
    155. future_join
    156. gen_future
    157. generic_assert_internals
    158. generic_atomic
    159. get_disjoint_mut_helpers
    160. get_mut_unchecked
    161. hash_set_entry
    162. hasher_prefixfree_extras
    163. hashmap_internals
    164. hint_must_use
    165. inplace_iteration
    166. int_format_into
    167. int_from_ascii
    168. int_roundings
    169. integer_atomics
    170. internal_impls_macro
    171. internal_output_capture
    172. io_const_error
    173. io_const_error_internals
    174. io_error_inprogress
    175. io_error_more
    176. io_error_uncategorized
    177. io_slice_as_bytes
    178. ip
    179. ip_as_octets
    180. ip_from
    181. is_ascii_octdigit
    182. is_loongarch_feature_detected
    183. is_riscv_feature_detected
    184. isolate_most_least_significant_one
    185. iter_advance_by
    186. iter_array_chunks
    187. iter_chain
    188. iter_collect_into
    189. iter_from_coroutine
    190. iter_intersperse
    191. iter_is_partitioned
    192. iter_macro
    193. iter_map_windows
    194. iter_next_chunk
    195. iter_order_by
    196. iter_partition_in_place
    197. iterator_try_collect
    198. iterator_try_reduce
    199. junction_point
    200. layout_for_ptr
    201. lazy_cell_into_inner
    202. lazy_get
    203. legacy_receiver_trait
    204. liballoc_internals
    205. libstd_sys_internals
    206. likely_unlikely
    207. linked_list_cursors
    208. linked_list_remove
    209. linked_list_retain
    210. linux_pidfd
    211. local_waker
    212. lock_value_accessors
    213. log_syntax
    214. map_try_insert
    215. mapped_lock_guards
    216. maybe_uninit_array_assume_init
    217. maybe_uninit_as_bytes
    218. maybe_uninit_fill
    219. maybe_uninit_slice
    220. maybe_uninit_uninit_array_transpose
    221. maybe_uninit_write_slice
    222. mem_copy_fn
    223. more_float_constants
    224. mpmc_channel
    225. mutex_data_ptr
    226. new_range_api
    227. new_zeroed_alloc
    228. next_index
    229. nonzero_bitwise
    230. nonzero_from_mut
    231. nonzero_internals
    232. nonzero_ops
    233. normalize_lexically
    234. numfmt
    235. once_cell_get_mut
    236. once_cell_try
    237. once_cell_try_insert
    238. one_sided_range
    239. option_array_transpose
    240. option_zip
    241. os_str_slice
    242. os_string_truncate
    243. panic_abort
    244. panic_always_abort
    245. panic_backtrace_config
    246. panic_can_unwind
    247. panic_internals
    248. panic_payload_as_str
    249. panic_unwind
    250. panic_update_hook
    251. partial_ord_chaining_methods
    252. path_add_extension
    253. path_file_prefix
    254. pattern
    255. pattern_type_macro
    256. pattern_type_range_trait
    257. peer_credentials_unix_socket
    258. phantom_variance_markers
    259. pin_coerce_unsized_trait
    260. pointer_is_aligned_to
    261. pointer_try_cast_aligned
    262. portable_simd
    263. prelude_future
    264. prelude_next
    265. print_internals
    266. proc_macro_def_site
    267. proc_macro_diagnostic
    268. proc_macro_expand
    269. proc_macro_internals
    270. proc_macro_quote
    271. proc_macro_span
    272. proc_macro_totokens
    273. proc_macro_tracked_env
    274. proc_macro_value
    275. process_chroot
    276. process_exitcode_internals
    277. process_internals
    278. profiler_runtime_lib
    279. ptr_alignment_type
    280. ptr_as_ref_unchecked
    281. ptr_as_uninit
    282. ptr_internals
    283. ptr_mask
    284. ptr_metadata
    285. pub_crate_should_not_need_unstable_attr
    286. random
    287. range_bounds_is_empty
    288. range_into_bounds
    289. raw_os_error_ty
    290. raw_slice_split
    291. raw_vec_internals
    292. read_buf
    293. reentrant_lock
    294. reentrant_lock_data_ptr
    295. restricted_std
    296. result_option_map_or_default
    297. round_char_boundary
    298. rt
    299. rwlock_data_ptr
    300. rwlock_downgrade
    301. sealed
    302. seek_io_take_position
    303. seek_stream_len
    304. set_ptr_value
    305. setgroups
    306. sgx_platform
    307. sized_type_properties
    308. slice_as_array
    309. slice_concat_ext
    310. slice_concat_trait
    311. slice_from_ptr_range
    312. slice_index_methods
    313. slice_internals
    314. slice_iter_mut_as_mut_slice
    315. slice_partition_dedup
    316. slice_pattern
    317. slice_ptr_get
    318. slice_range
    319. slice_split_once
    320. slice_swap_unchecked
    321. solid_ext
    322. sort_floats
    323. split_array
    324. split_as_slice
    325. std_internals
    326. stdarch_arm_feature_detection
    327. stdarch_mips_feature_detection
    328. stdarch_powerpc_feature_detection
    329. stdarch_s390x_feature_detection
    330. stdio_makes_pipe
    331. step_trait
    332. str_as_str
    333. str_from_raw_parts
    334. str_from_utf16_endian
    335. str_internals
    336. str_lines_remainder
    337. str_split_inclusive_remainder
    338. str_split_remainder
    339. str_split_whitespace_remainder
    340. strict_overflow_ops
    341. strict_provenance_atomic_ptr
    342. string_from_utf8_lossy_owned
    343. string_into_chars
    344. string_remove_matches
    345. substr_range
    346. sync_poison_mod
    347. sync_unsafe_cell
    348. tcp_deferaccept
    349. tcp_linger
    350. tcplistener_into_incoming
    351. temporary_niche_types
    352. test
    353. thin_box
    354. thread_id_value
    355. thread_local_internals
    356. thread_raw
    357. thread_sleep_until
    358. thread_spawn_hook
    359. trace_macros
    360. track_path
    361. transmutability
    362. trim_prefix_suffix
    363. trusted_fused
    364. trusted_len
    365. trusted_len_next_unchecked
    366. trusted_random_access
    367. trusted_step
    368. try_find
    369. try_reserve_kind
    370. try_trait_v2
    371. try_trait_v2_residual
    372. try_trait_v2_yeet
    373. try_with_capacity
    374. tuple_trait
    375. type_ascription
    376. ub_checks
    377. uefi_std
    378. uint_bit_width
    379. unchecked_neg
    380. unchecked_shifts
    381. unicode_internals
    382. unique_rc_arc
    383. unix_file_vectored_at
    384. unix_mkfifo
    385. unix_send_signal
    386. unix_set_mark
    387. unix_socket_ancillary_data
    388. unix_socket_exclbind
    389. unix_socket_peek
    390. unsafe_cell_access
    391. unsafe_pinned
    392. unsigned_nonzero_div_ceil
    393. unsigned_signed_diff
    394. unsize
    395. unwrap_infallible
    396. update_panic_count
    397. utf16_extra
    398. variant_count
    399. vec_deque_iter_as_slices
    400. vec_deque_pop_if
    401. vec_deque_truncate_front
    402. vec_into_chunks
    403. vec_into_raw_parts
    404. vec_peek_mut
    405. vec_push_within_capacity
    406. vec_split_at_spare
    407. wasi_ext
    408. windows_by_handle
    409. windows_c
    410. windows_change_time
    411. windows_handle
    412. windows_net
    413. windows_process_exit_code_from
    414. windows_process_extensions_async_pipes
    415. windows_process_extensions_force_quotes
    416. windows_process_extensions_main_thread_handle
    417. windows_process_extensions_raw_attribute
    418. windows_process_extensions_show_window
    419. windows_process_extensions_startupinfo
    420. windows_stdio
    421. wrapping_int_impl
    422. wrapping_next_power_of_two
    423. write_all_vectored
    424. yeet_desugar_details