-Z option triageAs of 2023-11-08, we have 185 unstable (-Z) options. Are they all necessary? Should some be stabilized? Let's crowdsource that question.
Please mark them as follows:
Note: The categories below are rough, and many options could go in more than one category. The exact category for each option doesn't really matter, it's just a way of structuring this document.
-Z dump-dep-graph=val – dump the dependency graph to $RUST_DEP_GRAPH (default: /tmp/dep_graph.gv) (default: no)-Z dump-mir=val – dump MIR state to file.val is used to select which passes and functions to dump. For example:all matches all passes and functions,foo matches all passes for functions whose name contains 'foo',foo & ConstProp only the 'ConstProp' pass for function names containing 'foo',foo | bar all passes for function names containing 'foo' or 'bar'.-Z dump-mir-dataflow=val – in addition to .mir files, create graphviz .dot files with dataflow results (default: no)-Z dump-mir-dir=val – the directory the MIR is dumped into (default: mir_dump)-Z dump-mir-exclude-pass-number=val – exclude the pass number when dumping MIR (used in tests) (default: no)-Z dump-mir-graphviz=val – in addition to .mir files, create graphviz .dot files (default: no)-Z dump-mir-spanview=val – in addition to .mir files, create .html files to view spans for all statements (including terminators), only terminator spans, or computed block spans (one span encompassing a block's terminator and all statements).-Z dump-mono-stats=val – output statistics about monomorphization collection-Z dump-mono-stats-format=val – the format to use for -Z dump-mono-stats (markdown (default) or json)-Z dump-solver-proof-tree=val – dump a proof tree for every goal evaluated by the new trait solver. If the flag is specified without any options after italways. If the flag is not specified at all it defaults to on-request.-Z graphviz-dark-mode=val – use dark-themed colors in graphviz output (default: no)-Z graphviz-font=val – use the given fontname in graphviz output; can be overridden by setting environment variable RUSTC_GRAPHVIZ_FONT (default: Courier, monospace)-Z hir-stats=val – print some statistics about AST and HIR (default: no)-Z input-stats in https://github.com/rust-lang/rust/pull/133023-Z incremental-info=val – print high-level information about incremental reuse (or the lack thereof) (default: no)-Z input-stats=val – gather statistics about the input (default: no)
-Z hir-stats-Z llvm-time-trace=val – generate JSON tracing data file from LLVM data (default: no)-Z meta-stats=val – gather metadata statistics (default: no)-Z mir-include-spans=val – use line numbers relative to the function in mir pretty printing-Z nll-facts=val – dump facts from NLL analysis into side files (default: no)-Z nll-facts-dir=val – the directory the NLL facts are dumped into (default: nll-facts)-Z perf-stats=val – print some performance-related statistics (default: no)-Z print-codegen-stats=val – print codegen statistics (default: no)-Z print-fuel=val – make rustc print the total optimization fuel used by a crate-Z print-llvm-passes=val – print the LLVM optimization passes being run (default: no)-Z print-mono-items=val – print the result of the monomorphization collection pass-Z print-type-sizes=val – print layout information for each type encountered (default: no)-Z print-vtable-sizes=val – print size comparison between old and new vtable layouts (default: no)
-Z profile-closures=val – profile size of closures-Z show-span=val – show spans for compiler debugging (expr|pat|ty)-Z span-free-formats=val – exclude spans when debug-printing compiler state (default: no)-Z unpretty=val – present the input source, unstable (and less-pretty) variants;normal, identified,expanded, expanded,identified,expanded,hygiene (with internal representations),ast-tree (raw AST before expansion),ast-tree,expanded (raw AST after expansion),hir (the HIR), hir,identified,hir,typed (HIR with types for each node),hir-tree (dump the raw HIR),thir-tree, thir-flat,mir (the MIR), or mir-cfg (graphviz formatted MIR)-Z verbose=val – in general, enable more debug printouts (default: no)
-Z assert-incr-state=val – assert that the incremental cache is in given state: either loaded or not-loaded.-Z incremental-verify-ich=val – verify incr. comp. hashes of green query instances (default: no)-Z validate-mir=val – validate MIR after each transformation-Z verify-llvm-ir=val – verify LLVM IR (default: no)-Z cross-crate-inline-threshold=val – threshold to allow cross crate inlining of functions-Z fuel=val – set the optimization fuel quota for a crate-Z inline-llvm=val – enable LLVM inlining (default: yes)-Z inline-mir=val – enable MIR inlining (default: no)-Z inline-mir-hint-threshold=val – inlining threshold for functions with inline hint (default: 100)-Z inline-mir-threshold=val – a default MIR inlining threshold (default: 50)-Z llvm-plugins=val – a list LLVM plugins to enable (space separated)-Z merge-functions=val – control the operation of the MergeFunctions LLVM pass, taking the same values as the target option of the same name-Z mir-enable-passes=val – use like -Zmir-enable-passes=+DestinationPropagation,-InstSimplify. Forces the specified passes to be enabled, overriding all other checks. In particular, this will enable unsound (known-buggy and hence usually disabled) passes without further warning! Passes that are not specified are enabled or disabled by other flags as usual.-Z mir-opt-level=val – MIR optimization level (0-4; default: 1 in non optimized builds and 2 in optimized builds)-Z polymorphize=val – perform polymorphization analysis-Z remark-dir=val – directory into which to write optimization remarks (if not specified, they will be written to standard error output)-Z unsound-mir-opts=val – enable unsound and buggy MIR optimizations (default: no)-Z virtual-function-elimination=val – enables dead virtual function elimination optimization. Requires -Clto[=[fat,yes]]-Z unleash-the-miri-inside-of-you=val – take the brakes off const evaluation. NOTE: this is unsound (default: no)-Z asm-comments=val – generate comments into the assembly (may change behavior) (default: no)-Z box-noalias=val – emit noalias metadata for box (default: yes)-Z branch-protection=val – set options for branch target identification and pointer authentication on AArch64-Z cf-protection=val – instrument control-flow architecture protection-Z codegen-backend=val – the backend to use-Z combine-cgu=val – combine CGUs into a single one-Z emit-stack-sizes=val – emit a section containing stack size metadata (default: no)-Z export-executable-symbols=val – export symbols from executables, as if they were dynamic libraries-Z extra-const-ub-checks=val – turns on more checks to detect const UB, which can be slow (default: no)-Z function-sections=val – whether each function should go in its own section-Z human-readable-cgu-names=val – generate human-readable, predictable names for codegen units (default: no)-Z inline-in-all-cgus=val – control whether #[inline] functions are in all CGUs
-Z instrument-mcount=val – insert function instrument code for mcount-based tracing (default: no)-Z instrument-xray=val – insert function instrument code for XRay-based tracing (default: no)=always=never=ignore-loops=instruction-threshold=N=skip-entry=skip-exit-Z mutable-noalias=val – emit noalias metadata for mutable references (default: yes)-Z no-jump-tables=val – disable the jump tables and lookup tables that can be generated from a switch case lowering-Z no-trait-vptr=val – disable generation of trait vptr in vtable for upcasting-Z no-unique-section-names=val – do not use unique names for text and data sections when -Z function-sections is used-Z packed-bundled-libs=val – change rlib format to store native libraries as archives-Z plt=val – whether to use the PLT when calling into shared libraries;-Z precise-enum-drop-elaboration=val – use a more precise version of drop elaboration for matches on enums (default: yes). This results in better codegen, but has caused miscompilations on some tier 2 platforms. See #77382 and #74551.-Z relax-elf-relocations=val – whether ELF relocations can be relaxed-Z relro-level=val – choose which RELRO level to use-Z saturating-float-casts=val – make float->int casts UB-free: numbers outside the integer type's range are clipped to the max/min integer respectively, and NaN is mapped to 0 (default: yes)-Z share-generics=val – make the current crate share its generic instantiations-Z stack-protector=val – control stack smash protection strategy (rustc --print stack-protector-strategies for details)-Z trap-unreachable=val – generate trap instructions for unreachable intrinsics (default: use target setting, usually yes)-Z tune-cpu=val – select processor to schedule for (rustc --print target-cpus for details)-Z use-ctors-section=val – use legacy .ctors section for initializers rather than .init_array-Z link-directives=val – honor #[link] directives in the compiled crate (default: yes)-Z link-native-libraries=val – link native libraries in the linker invocation (default: yes)-Z link-only=val – link the .rlink file generated by -Z no-link (default: no)-Z osx-rpath-install-name=val – pass -install_name @rpath/... to the macOS linker (default: no)-Z pre-link-arg=val – a single extra argument to prepend the linker invocation (can be used several times)
-Z pre-link-arg and -Z pre-link-args-Z pre-link-args=val – extra arguments to prepend to the linker invocation (space separated)-Z staticlib-prefer-dynamic=val – prefer dynamic linking to static linking for staticlibs (default: no)-Z strip=val – tell the linker which information to strip (none (default), debuginfo or symbols)-Z no-analysis=val – parse and expand the source, but run no analysis-Z no-codegen=val – run all passes except codegen; no output-Z no-link=val – compile without linking-Z parse-crate-root-only=val – parse the crate root file only; do not parse other files, compile, assemble, or link (default: no)-Z sanitizer=val – use a sanitizer-Z sanitizer-cfi-canonical-jump-tables=val – enable canonical jump tables (default: yes)-Z sanitizer-cfi-generalize-pointers=val – enable generalizing pointer types (default: no)-Z sanitizer-cfi-normalize-integers=val – enable normalizing integer types (default: no)-Z sanitizer-memory-track-origins=val – enable origins tracking in MemorySanitizer-Z sanitizer-recover=val – enable recovery for selected sanitizers-Z future-incompat-test=val – forces all lints to be future incompatible, used for internal testing (default: no)-Z incremental-ignore-spans=val – ignore spans during ICH computation – used for testing (default: no)-Z simulate-remapped-rust-src-base=val – simulate the effect of remap-debuginfo = true at bootstrapping by remapping path to rust's source base directory. only meant for testing purposes-Z translate-additional-ftl=val – additional fluent translation to preferentially use (for testing translation)-Z ui-testing=val – emit compiler diagnostics in a form suitable for UI testing (default: no)-Z no-leak-check=val – disable the 'leak check' for subtyping; unsound, but useful for tests-Z query-dep-graph=val – enable queries of the dependency graph for regression testing (default: no)-Z tiny-const-eval-limit=val – sets a tiny, non-configurable limit for const eval; useful for compiler tests-Z debug-macros=val – emit line numbers debug info inside macros (default: no)-Z debuginfo-compression=val – compress debug info sections (none, zlib, zstd, default: none)-Z dwarf-version=val – version of DWARF debug information to emit (default: 2 or 4, depending on platform)-Z no-generate-arange-section=val – omit DWARF address ranges that give faster lookups-Z split-dwarf-inlining=val – provide minimal debug info in the object/executable to facilitate online symbolication/stack traces in the absence of .dwo/.dwp files when using Split DWARF
-Z split-dwarf-kind=val – split dwarf variant (only if -Csplit-debuginfo is enabled and on relevant platform)split)split: sections which do not require relocation are written into a DWARF object (.dwo)single: sections which do not require relocation are written into object file but ignored-Z src-hash-algorithm=val – hash algorithm of source files in debug info (md5, sha1, or sha256)-Z always-encode-mir=val – encode MIR of all functions into the crate metadata (default: no)-Z binary-dep-depinfo=val – include artifacts (sysroot, crate dependencies) used during compilation in dep-info (default: no)-Z dep-info-omit-d-target=val – in dep-info output, omit targets for tracking dependencies of the dep-info files themselves (default: no)-Z ls=val – decode and print various parts of the crate metadata for a library crate (space separated)-Z no-profiler-runtime=val – prevent automatic injection of the profiler_builtins crate
-Z profile=val – insert profiling code (default: no)-Z profile-emit=val – file path to emit profiling data at runtime when using 'profile' (default based on relative source path)-Z profiler-runtime=val – name of the profiler runtime crate to automatically inject (default: profiler_builtins)AutoFDO is a form of profile-guided optimization, separate from the compiler's main PGO features. Untested in-tree.
-Z debug-info-for-profiling=val – emit discriminators and other data necessary for AutoFDO-Z profile-sample-use=val – use the given .prof file for sampled profile-guided optimization (also known as AutoFDO)-Z location-detail=val – what location details should be tracked when using caller_location, either none, or a comma separated list of location details, for which valid options are file, line, and column (default: file,line,column)-Z self-profile=val – run the self profiler and output the raw event data
-Z self-profile-counter=val – counter used by the self profiler (default: wall-time), one of:wall-time (monotonic clock, i.e. std::time::Instant)instructions:u (retired instructions, userspace-only)instructions-minus-irqs:u (subtracting hardware interrupt counts for extra accuracy)
-Z self-profile-events=val – specify the events recorded by the self profiler;-Z self-profile-events=default,query-keys-Z time-llvm-passes=val – measure time of each LLVM pass (default: no)-Z time-passes=val – measure time of each rustc pass (default: no)
-Z time-passes-format=val – the format to use for -Z time-passes (text (default) or json)-Z deduplicate-diagnostics=val – deduplicate identical diagnostics (default: yes)-Z dont-buffer-diagnostics=val – emit diagnostics rather than buffering (breaks NLL error downgrading, sorting) (default: no)-Z eagerly-emit-delayed-bugs – emit delayed bugs eagerly as errors instead of stashing them and emitting them only if an error has not been emitted"
-Z report-delayed-bugs, because it's a little simpler and more convenient to use-Z ignore-directory-in-diagnostics-source-blocks=val – do not display the source code block in diagnostics for files in the directory
src/tools/compiletest to avoid differences when $CARGO_HOME is remapped.-Z report-delayed-bugs=val – immediately print bugs registered with delay_span_bug (default: no)-Z teach=val – show extended diagnostic help (default: no)-Z terminal-urls=val – use the OSC 8 hyperlink terminal specification to print hyperlinks in the compiler output
-Z track-diagnostics=val – tracks where in rustc a diagnostic was emitted
-Z translate-directionality-markers=val – emit directionality isolation markers in translated diagnostics-Z translate-lang=val – language identifier for diagnostic output-Z treat-err-as-bug=val – treat the valth error that occurs as bug (default if not specified: 0 - don't treat errors as bugs. default if specified without a value: 1 - treat the first error as bug)-Z trim-diagnostic-paths=val – in diagnostics, use heuristics to shorten paths referring to items
true. Set to false in a few tests, presumably to ensure the full path is correct-Z write-long-types-to-disk=val – whether long type names should be written to files instead of being printed in errors-Z dual-proc-macros=val – load proc macros for both target and host, but only link to the target (default: no)-Z macro-backtrace=val – show macro backtraces (default: no)-Z proc-macro-backtrace=val – show backtraces for panics during proc-macro execution (default: no)-Z proc-macro-execution-strategy=val – how to run proc-macro code (default: same-thread)-Z span-debug=val – forward proc_macro::Span's Debug impl to Span-Z trace-macros=val – for every macro invocation, print its name and arguments (default: no)-Z split-lto-unit=val – enable LTO unit splitting (default: no) Stabilize: Required to build Chromium, users shouldn't need a nightly compiler for that.-Z thinlto=val – enable ThinLTO when possible-Z dylib-lto=val – enables LTO for dylib crate type-Z emit-thin-lto=val – emit the bc module with thin LTO info (default: yes)-Z allow-features=val – only allow the listed language features to be enabled in code (comma separated)-Z assume-incomplete-release=val – make cfg(version) treat the current version as incomplete (default: no)-Z crate-attr=val – inject the given attribute in the crate-Z fewer-names=val – reduce memory use by retaining fewer names within compilation artifacts (LLVM-IR) (default: no)-Z flatten-format-args=val – flatten nested format_args!() and literals into a simplified format_args!() call (default: yes)-Z force-unstable-if-unmarked=val – force all crates to be rustc_private unstable (default: no)-Z identify-regions=val – display unnamed regions as '<id>, using a non-ident unique id (default: no)-Z keep-hygiene-data=val – keep hygiene data after analysis (default: no)-Z layout-seed=val – seed layout randomization-Z maximal-hir-to-mir-coverage=val – save as much information as possible about the correspondence between MIR and HIR as source scopes (default: no)-Z mir-emit-retag=val – emit Retagging MIR statements, interpreted e.g., by miri; implies -Zmir-opt-level=0 (default: no)-Z mir-keep-place-mention=val – keep place mention MIR statements, interpreted e.g., by miri; implies -Zmir-opt-level=0 (default: no)-Z move-size-limit=val – the size at which the large_assignments lint starts to be emitted-Z no-parallel-backend=val – run LLVM in non-parallel mode (while keeping codegen-units and ThinLTO)
-Z normalize-docs=val – normalize associated items in rustdoc when generating documentation-Z oom=val – panic strategy for out-of-memory handling-Z panic-abort-tests=val – support compiling tests with panic=abort (default: no)-Z panic-in-drop=val – panic strategy for panics in drops-Z polonius=val – enable polonius-based borrow-checker (default: no)-Z randomize-layout=val – randomize the layout of types (default: no)-Z remap-cwd-prefix=val – remap paths under the current working directory to this path prefix-Z remap-path-scope=val – remap path scope (default: all)-Z staticlib-allow-rdylib-deps=val – allow staticlibs to have rust dylib dependencies-Z strict-init-checks=val – control if mem::uninitialized and mem::zeroed panic on more UB-Z temps-dir=val – the directory the intermediate files are written to-Z thir-unsafeck=val – use the THIR unsafety checker (default: no)-Z threads=val – use a thread pool with N threads
-Z tls-model=val – choose the TLS model to use (rustc --print tls-models for details)-Z trait-solver=val – specify the trait solver mode used by rustc (default: classic)-Z translate-remapped-path-to-local-path=val – translate remapped paths into local paths when possible (default: yes)-Z uninit-const-chunk-threshold=val – allow generating const initializers with mixed init/uninit chunks, and set the maximum number of chunks for which this is allowed (default: 16)-Z unstable-options=val – adds unstable command line options to rustc interface (default: no)-Z wasi-exec-model=val – whether to build a wasi command or reactor
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