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. dyn_star
    87. ergonomic_clones
    88. ermsb_target_feature
    89. exhaustive_patterns
    90. explicit_extern_abis
    91. explicit_tail_calls
    92. export_stable
    93. extended_varargs_abi_support
    94. extern_system_varargs
    95. extern_types
    96. f128
    97. f16
    98. ffi_const
    99. ffi_pure
    100. fmt_debug
    101. fn_align
    102. fn_delegation
    103. freeze_impls
    104. frontmatter
    105. fundamental
    106. gen_blocks
    107. generic_assert
    108. generic_const_exprs
    109. generic_const_items
    110. generic_const_parameter_types
    111. generic_pattern_types
    112. global_registration
    113. guard_patterns
    114. half_open_range_patterns_in_slices
    115. hexagon_target_feature
    116. if_let_guard
    117. impl_trait_in_assoc_type
    118. impl_trait_in_bindings
    119. impl_trait_in_fn_trait_return
    120. import_trait_associated_functions
    121. inherent_associated_types
    122. intra_doc_pointers
    123. intrinsics
    124. lahfsahf_target_feature
    125. lang_items
    126. large_assignments
    127. lazy_type_alias
    128. let_chains
    129. link_arg_attribute
    130. link_cfg
    131. link_llvm_intrinsics
    132. linkage
    133. loongarch_target_feature
    134. loop_match
    135. m68k_target_feature
    136. macro_metavar_expr
    137. macro_metavar_expr_concat
    138. marker_trait_attr
    139. min_generic_const_args
    140. min_specialization
    141. mips_target_feature
    142. more_maybe_bounds
    143. more_qualified_paths
    144. movrs_target_feature
    145. multiple_supertrait_upcastable
    146. must_not_suspend
    147. mut_ref
    148. naked_functions_rustic_abi
    149. naked_functions_target_feature
    150. native_link_modifiers_as_needed
    151. needs_panic_runtime
    152. negative_bounds
    153. negative_impls
    154. never_patterns
    155. never_type
    156. never_type_fallback
    157. new_range
    158. no_core
    159. no_sanitize
    160. non_exhaustive_omitted_patterns_lint
    161. non_lifetime_binders
    162. offset_of_enum
    163. offset_of_slice
    164. omit_gdb_pretty_printer_section
    165. optimize_attribute
    166. panic_runtime
    167. patchable_function_entry
    168. pattern_complexity_limit
    169. pattern_types
    170. pin_ergonomics
    171. postfix_match
    172. powerpc_target_feature
    173. prelude_import
    174. prfchw_target_feature
    175. proc_macro_hygiene
    176. profiler_runtime
    177. raw_dylib_elf
    178. ref_pat_eat_one_layer_2024
    179. ref_pat_eat_one_layer_2024_structural
    180. register_tool
    181. repr_simd
    182. return_type_notation
    183. riscv_target_feature
    184. rtm_target_feature
    185. rust_cold_cc
    186. rustc_allow_const_fn_unstable
    187. rustc_attrs
    188. rustc_private
    189. rustdoc_internals
    190. rustdoc_missing_doc_code_examples
    191. s390x_target_feature
    192. simd_ffi
    193. sized_hierarchy
    194. sparc_target_feature
    195. specialization
    196. sse4a_target_feature
    197. staged_api
    198. stmt_expr_attributes
    199. strict_provenance_lints
    200. string_deref_patterns
    201. structural_match
    202. super_let
    203. supertrait_item_shadowing
    204. tbm_target_feature
    205. test_unstable_lint
    206. thread_local
    207. trait_alias
    208. transmute_generic_consts
    209. transparent_unions
    210. trivial_bounds
    211. try_blocks
    212. type_alias_impl_trait
    213. type_changing_struct_update
    214. unboxed_closures
    215. unqualified_local_imports
    216. unsafe_binders
    217. unsafe_fields
    218. unsized_const_params
    219. unsized_fn_params
    220. used_with_arg
    221. wasm_target_feature
    222. where_clause_attrs
    223. with_negative_coherence
    224. x86_amx_intrinsics
    225. x87_target_feature
    226. xop_target_feature
    227. yeet_expr
    228. 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. bound_as_ref
    37. box_as_ptr
    38. box_into_boxed_slice
    39. box_into_inner
    40. box_vec_non_null
    41. breakpoint
    42. bstr
    43. bstr_internals
    44. btree_cursors
    45. btree_entry_insert
    46. btree_extract_if
    47. btree_set_entry
    48. btreemap_alloc
    49. buf_read_has_data_left
    50. bufreader_peek
    51. c_size_t
    52. c_void_variant
    53. can_vector
    54. cell_leak
    55. cfg_accessible
    56. cfg_eval
    57. cfg_select
    58. char_internals
    59. char_max_len
    60. clone_to_uninit
    61. cmp_minmax
    62. coerce_pointee_validated
    63. coerce_unsized
    64. cold_path
    65. concat_bytes
    66. const_alloc_error
    67. const_array_each_ref
    68. const_btree_len
    69. const_carrying_mul_add
    70. const_clone
    71. const_cmp
    72. const_deref
    73. const_eval_select
    74. const_float_round_methods
    75. const_format_args
    76. const_heap
    77. const_ops
    78. const_pathbuf_osstring_new
    79. const_range_bounds
    80. const_raw_ptr_comparison
    81. const_ref_cell
    82. const_slice_from_mut_ptr_range
    83. const_slice_from_ptr_range
    84. const_slice_make_iter
    85. const_slice_reverse
    86. const_split_off_first_last
    87. const_type_id
    88. const_type_name
    89. container_error_extra
    90. context_ext
    91. control_flow_into_value
    92. convert_float_to_int
    93. core_float_math
    94. core_intrinsics
    95. core_intrinsics_fallbacks
    96. core_io_borrowed_buf
    97. core_private_bignum
    98. core_private_diy_float
    99. coroutine_trait
    100. cow_is_borrowed
    101. cstr_bytes
    102. cstr_display
    103. cstr_internals
    104. cursor_split
    105. deadline_api
    106. debug_closure_helpers
    107. dec2flt
    108. deref_pure_trait
    109. derive_clone_copy
    110. derive_coerce_pointee
    111. derive_const
    112. derive_eq
    113. dir_entry_ext2
    114. discriminant_kind
    115. disjoint_bitor
    116. dispatch_from_dyn
    117. downcast_unchecked
    118. drain_keep_rest
    119. duration_constants
    120. duration_constructors
    121. duration_constructors_lite
    122. duration_millis_float
    123. duration_units
    124. edition_panic
    125. error_generic_member_access
    126. error_iter
    127. error_reporter
    128. error_type_id
    129. exact_div
    130. exact_size_is_empty
    131. exclusive_wrapper
    132. exit_status_error
    133. exitcode_exit_method
    134. extend_one
    135. extend_one_unchecked
    136. fd
    137. fd_read
    138. file_buffered
    139. file_with_nul
    140. float_algebraic
    141. float_erf
    142. float_gamma
    143. float_minimum_maximum
    144. flt2dec
    145. fmt_helpers_for_derive
    146. fmt_internals
    147. fn_ptr_trait
    148. fn_traits
    149. forget_unsized
    150. format_args_nl
    151. formatting_options
    152. freeze
    153. future_join
    154. gen_future
    155. generic_assert_internals
    156. generic_atomic
    157. get_disjoint_mut_helpers
    158. get_mut_unchecked
    159. hash_set_entry
    160. hasher_prefixfree_extras
    161. hashmap_internals
    162. hint_must_use
    163. inplace_iteration
    164. int_from_ascii
    165. int_roundings
    166. integer_atomics
    167. internal_impls_macro
    168. internal_output_capture
    169. io_const_error
    170. io_const_error_internals
    171. io_error_inprogress
    172. io_error_more
    173. io_error_uncategorized
    174. io_slice_as_bytes
    175. ip
    176. ip_as_octets
    177. ip_from
    178. is_ascii_octdigit
    179. is_loongarch_feature_detected
    180. is_riscv_feature_detected
    181. isolate_most_least_significant_one
    182. iter_advance_by
    183. iter_array_chunks
    184. iter_chain
    185. iter_collect_into
    186. iter_from_coroutine
    187. iter_intersperse
    188. iter_is_partitioned
    189. iter_macro
    190. iter_map_windows
    191. iter_next_chunk
    192. iter_order_by
    193. iter_partition_in_place
    194. iterator_try_collect
    195. iterator_try_reduce
    196. junction_point
    197. layout_for_ptr
    198. lazy_cell_into_inner
    199. lazy_get
    200. legacy_receiver_trait
    201. liballoc_internals
    202. libstd_sys_internals
    203. likely_unlikely
    204. linked_list_cursors
    205. linked_list_remove
    206. linked_list_retain
    207. linux_pidfd
    208. local_waker
    209. lock_value_accessors
    210. log_syntax
    211. map_try_insert
    212. mapped_lock_guards
    213. maybe_uninit_array_assume_init
    214. maybe_uninit_as_bytes
    215. maybe_uninit_fill
    216. maybe_uninit_slice
    217. maybe_uninit_uninit_array_transpose
    218. maybe_uninit_write_slice
    219. mem_copy_fn
    220. mixed_integer_ops_unsigned_sub
    221. more_float_constants
    222. mpmc_channel
    223. mutex_data_ptr
    224. new_range_api
    225. new_zeroed_alloc
    226. next_index
    227. nonzero_bitwise
    228. nonzero_from_mut
    229. nonzero_internals
    230. nonzero_ops
    231. normalize_lexically
    232. numfmt
    233. once_cell_get_mut
    234. once_cell_try
    235. once_cell_try_insert
    236. one_sided_range
    237. option_array_transpose
    238. option_zip
    239. os_str_slice
    240. os_string_truncate
    241. panic_abort
    242. panic_always_abort
    243. panic_backtrace_config
    244. panic_can_unwind
    245. panic_internals
    246. panic_payload_as_str
    247. panic_unwind
    248. panic_update_hook
    249. partial_ord_chaining_methods
    250. path_add_extension
    251. path_file_prefix
    252. pattern
    253. pattern_type_macro
    254. pattern_type_range_trait
    255. peer_credentials_unix_socket
    256. phantom_variance_markers
    257. pin_coerce_unsized_trait
    258. pointer_is_aligned_to
    259. pointer_like_trait
    260. pointer_try_cast_aligned
    261. portable_simd
    262. prelude_future
    263. prelude_next
    264. print_internals
    265. proc_macro_def_site
    266. proc_macro_diagnostic
    267. proc_macro_expand
    268. proc_macro_internals
    269. proc_macro_quote
    270. proc_macro_span
    271. proc_macro_totokens
    272. proc_macro_tracked_env
    273. proc_macro_value
    274. process_chroot
    275. process_exitcode_internals
    276. process_internals
    277. profiler_runtime_lib
    278. ptr_alignment_type
    279. ptr_as_ref_unchecked
    280. ptr_as_uninit
    281. ptr_internals
    282. ptr_mask
    283. ptr_metadata
    284. pub_crate_should_not_need_unstable_attr
    285. random
    286. range_bounds_is_empty
    287. range_into_bounds
    288. raw_os_error_ty
    289. raw_slice_split
    290. raw_vec_internals
    291. read_buf
    292. reentrant_lock
    293. reentrant_lock_data_ptr
    294. restricted_std
    295. result_option_map_or_default
    296. round_char_boundary
    297. rt
    298. rwlock_data_ptr
    299. rwlock_downgrade
    300. sealed
    301. seek_io_take_position
    302. seek_stream_len
    303. set_ptr_value
    304. setgroups
    305. sgx_platform
    306. sized_type_properties
    307. slice_as_array
    308. slice_concat_ext
    309. slice_concat_trait
    310. slice_from_ptr_range
    311. slice_index_methods
    312. slice_internals
    313. slice_iter_mut_as_mut_slice
    314. slice_partition_dedup
    315. slice_pattern
    316. slice_ptr_get
    317. slice_range
    318. slice_split_once
    319. slice_swap_unchecked
    320. solid_ext
    321. sort_floats
    322. split_array
    323. split_as_slice
    324. std_internals
    325. stdarch_arm_feature_detection
    326. stdarch_mips_feature_detection
    327. stdarch_powerpc_feature_detection
    328. stdarch_s390x_feature_detection
    329. stdio_makes_pipe
    330. step_trait
    331. str_as_str
    332. str_from_raw_parts
    333. str_from_utf16_endian
    334. str_internals
    335. str_lines_remainder
    336. str_split_inclusive_remainder
    337. str_split_remainder
    338. str_split_whitespace_remainder
    339. strict_overflow_ops
    340. strict_provenance_atomic_ptr
    341. string_from_utf8_lossy_owned
    342. string_into_chars
    343. string_remove_matches
    344. substr_range
    345. sync_poison_mod
    346. sync_unsafe_cell
    347. tcp_deferaccept
    348. tcp_linger
    349. tcplistener_into_incoming
    350. temporary_niche_types
    351. test
    352. thin_box
    353. thread_id_value
    354. thread_local_internals
    355. thread_raw
    356. thread_sleep_until
    357. thread_spawn_hook
    358. trace_macros
    359. track_path
    360. transmutability
    361. trim_prefix_suffix
    362. trusted_fused
    363. trusted_len
    364. trusted_len_next_unchecked
    365. trusted_random_access
    366. trusted_step
    367. try_find
    368. try_reserve_kind
    369. try_trait_v2
    370. try_trait_v2_residual
    371. try_trait_v2_yeet
    372. try_with_capacity
    373. tuple_trait
    374. type_ascription
    375. ub_checks
    376. uefi_std
    377. uint_bit_width
    378. unchecked_neg
    379. unchecked_shifts
    380. unicode_internals
    381. unique_rc_arc
    382. unix_file_vectored_at
    383. unix_mkfifo
    384. unix_send_signal
    385. unix_set_mark
    386. unix_socket_ancillary_data
    387. unix_socket_exclbind
    388. unix_socket_peek
    389. unsafe_cell_access
    390. unsafe_pinned
    391. unsigned_nonzero_div_ceil
    392. unsigned_signed_diff
    393. unsize
    394. unwrap_infallible
    395. update_panic_count
    396. utf16_extra
    397. variant_count
    398. vec_deque_iter_as_slices
    399. vec_deque_pop_if
    400. vec_deque_truncate_front
    401. vec_into_raw_parts
    402. vec_peek_mut
    403. vec_push_within_capacity
    404. vec_split_at_spare
    405. wasi_ext
    406. windows_by_handle
    407. windows_c
    408. windows_change_time
    409. windows_handle
    410. windows_net
    411. windows_process_exit_code_from
    412. windows_process_extensions_async_pipes
    413. windows_process_extensions_force_quotes
    414. windows_process_extensions_main_thread_handle
    415. windows_process_extensions_raw_attribute
    416. windows_process_extensions_show_window
    417. windows_process_extensions_startupinfo
    418. windows_stdio
    419. wrapping_int_impl
    420. wrapping_next_power_of_two
    421. write_all_vectored
    422. yeet_desugar_details