1 // Copyright 2014-2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! [Flexible target specification.](https://github.com/rust-lang/rfcs/pull/131)
13 //! Rust targets a wide variety of usecases, and in the interest of flexibility,
14 //! allows new target triples to be defined in configuration files. Most users
15 //! will not need to care about these, but this is invaluable when porting Rust
16 //! to a new platform, and allows for an unprecedented level of control over how
17 //! the compiler works.
19 //! # Using custom targets
21 //! A target triple, as passed via `rustc --target=TRIPLE`, will first be
22 //! compared against the list of built-in targets. This is to ease distributing
23 //! rustc (no need for configuration files) and also to hold these built-in
24 //! targets as immutable and sacred. If `TRIPLE` is not one of the built-in
25 //! targets, rustc will check if a file named `TRIPLE` exists. If it does, it
26 //! will be loaded as the target configuration. If the file does not exist,
27 //! rustc will search each directory in the environment variable
28 //! `RUST_TARGET_PATH` for a file named `TRIPLE.json`. The first one found will
29 //! be loaded. If no file is found in any of those directories, a fatal error
32 //! Projects defining their own targets should use
33 //! `--target=path/to/my-awesome-platform.json` instead of adding to
34 //! `RUST_TARGET_PATH`.
36 //! # Defining a new target
38 //! Targets are defined using [JSON](http://json.org/). The `Target` struct in
39 //! this module defines the format the JSON file should take, though each
40 //! underscore in the field names should be replaced with a hyphen (`-`) in the
41 //! JSON file. Some fields are required in every target specification, such as
42 //! `llvm-target`, `target-endian`, `target-pointer-width`, `data-layout`,
43 //! `arch`, and `os`. In general, options passed to rustc with `-C` override
44 //! the target's settings, though `target-feature` and `link-args` will *add*
45 //! to the list specified by the target, rather than replace.
47 use serialize::json::{Json, ToJson};
48 use std::collections::BTreeMap;
49 use std::default::Default;
50 use std::io::prelude::*;
65 mod windows_msvc_base;
67 pub type TargetResult = Result<Target, String>;
69 macro_rules! supported_targets {
70 ( $(($triple:expr, $module:ident)),+ ) => (
73 /// List of supported targets
74 const TARGETS: &'static [&'static str] = &[$($triple),*];
76 fn load_specific(target: &str) -> TargetResult {
80 let mut t = try!($module::target());
81 t.options.is_builtin = true;
83 // round-trip through the JSON parser to ensure at
84 // run-time that the parser works correctly
85 t = try!(Target::from_json(t.to_json()));
86 debug!("Got builtin target: {:?}", t);
90 _ => Err(format!("Unable to find target: {}", target))
94 pub fn get_targets() -> Box<Iterator<Item=String>> {
95 Box::new(TARGETS.iter().filter_map(|t| -> Option<String> {
97 .and(Ok(t.to_string()))
103 mod test_json_encode_decode {
104 use serialize::json::ToJson;
106 $(use super::$module;)*
111 // Grab the TargetResult struct. If we successfully retrieved
112 // a Target, then the test JSON encoding/decoding can run for this
113 // Target on this testing platform (i.e., checking the iOS targets
114 // only on a Mac test platform).
115 let _ = $module::target().map(|original| {
116 let as_json = original.to_json();
117 let parsed = Target::from_json(as_json).unwrap();
118 assert_eq!(original, parsed);
127 ("x86_64-unknown-linux-gnu", x86_64_unknown_linux_gnu),
128 ("i686-unknown-linux-gnu", i686_unknown_linux_gnu),
129 ("i586-unknown-linux-gnu", i586_unknown_linux_gnu),
130 ("mips-unknown-linux-gnu", mips_unknown_linux_gnu),
131 ("mipsel-unknown-linux-gnu", mipsel_unknown_linux_gnu),
132 ("powerpc-unknown-linux-gnu", powerpc_unknown_linux_gnu),
133 ("powerpc64-unknown-linux-gnu", powerpc64_unknown_linux_gnu),
134 ("powerpc64le-unknown-linux-gnu", powerpc64le_unknown_linux_gnu),
135 ("s390x-unknown-linux-gnu", s390x_unknown_linux_gnu),
136 ("arm-unknown-linux-gnueabi", arm_unknown_linux_gnueabi),
137 ("arm-unknown-linux-gnueabihf", arm_unknown_linux_gnueabihf),
138 ("arm-unknown-linux-musleabi", arm_unknown_linux_musleabi),
139 ("arm-unknown-linux-musleabihf", arm_unknown_linux_musleabihf),
140 ("armv7-unknown-linux-gnueabihf", armv7_unknown_linux_gnueabihf),
141 ("armv7-unknown-linux-musleabihf", armv7_unknown_linux_musleabihf),
142 ("aarch64-unknown-linux-gnu", aarch64_unknown_linux_gnu),
143 ("x86_64-unknown-linux-musl", x86_64_unknown_linux_musl),
144 ("i686-unknown-linux-musl", i686_unknown_linux_musl),
145 ("mips-unknown-linux-musl", mips_unknown_linux_musl),
146 ("mipsel-unknown-linux-musl", mipsel_unknown_linux_musl),
147 ("mips-unknown-linux-uclibc", mips_unknown_linux_uclibc),
148 ("mipsel-unknown-linux-uclibc", mipsel_unknown_linux_uclibc),
150 ("i686-linux-android", i686_linux_android),
151 ("arm-linux-androideabi", arm_linux_androideabi),
152 ("armv7-linux-androideabi", armv7_linux_androideabi),
153 ("aarch64-linux-android", aarch64_linux_android),
155 ("i686-unknown-freebsd", i686_unknown_freebsd),
156 ("x86_64-unknown-freebsd", x86_64_unknown_freebsd),
158 ("i686-unknown-dragonfly", i686_unknown_dragonfly),
159 ("x86_64-unknown-dragonfly", x86_64_unknown_dragonfly),
161 ("x86_64-unknown-bitrig", x86_64_unknown_bitrig),
162 ("x86_64-unknown-openbsd", x86_64_unknown_openbsd),
163 ("x86_64-unknown-netbsd", x86_64_unknown_netbsd),
164 ("x86_64-rumprun-netbsd", x86_64_rumprun_netbsd),
166 ("x86_64-apple-darwin", x86_64_apple_darwin),
167 ("i686-apple-darwin", i686_apple_darwin),
169 ("i386-apple-ios", i386_apple_ios),
170 ("x86_64-apple-ios", x86_64_apple_ios),
171 ("aarch64-apple-ios", aarch64_apple_ios),
172 ("armv7-apple-ios", armv7_apple_ios),
173 ("armv7s-apple-ios", armv7s_apple_ios),
175 ("x86_64-sun-solaris", x86_64_sun_solaris),
177 ("x86_64-pc-windows-gnu", x86_64_pc_windows_gnu),
178 ("i686-pc-windows-gnu", i686_pc_windows_gnu),
180 ("x86_64-pc-windows-msvc", x86_64_pc_windows_msvc),
181 ("i686-pc-windows-msvc", i686_pc_windows_msvc),
182 ("i586-pc-windows-msvc", i586_pc_windows_msvc),
184 ("le32-unknown-nacl", le32_unknown_nacl),
185 ("asmjs-unknown-emscripten", asmjs_unknown_emscripten)
188 /// Everything `rustc` knows about how to compile for a specific target.
190 /// Every field here must be specified, and has no default value.
191 #[derive(PartialEq, Clone, Debug)]
193 /// Target triple to pass to LLVM.
194 pub llvm_target: String,
195 /// String to use as the `target_endian` `cfg` variable.
196 pub target_endian: String,
197 /// String to use as the `target_pointer_width` `cfg` variable.
198 pub target_pointer_width: String,
199 /// OS name to use for conditional compilation.
200 pub target_os: String,
201 /// Environment name to use for conditional compilation.
202 pub target_env: String,
203 /// Vendor name to use for conditional compilation.
204 pub target_vendor: String,
205 /// Architecture to use for ABI considerations. Valid options: "x86",
206 /// "x86_64", "arm", "aarch64", "mips", "powerpc", and "powerpc64".
208 /// [Data layout](http://llvm.org/docs/LangRef.html#data-layout) to pass to LLVM.
209 pub data_layout: String,
210 /// Optional settings with defaults.
211 pub options: TargetOptions,
214 /// Optional aspects of a target specification.
216 /// This has an implementation of `Default`, see each field for what the default is. In general,
217 /// these try to take "minimal defaults" that don't assume anything about the runtime they run in.
218 #[derive(PartialEq, Clone, Debug)]
219 pub struct TargetOptions {
220 /// Whether the target is built-in or loaded from a custom target specification.
221 pub is_builtin: bool,
223 /// Linker to invoke. Defaults to "cc".
225 /// Archive utility to use when managing archives. Defaults to "ar".
228 /// Linker arguments that are unconditionally passed *before* any
229 /// user-defined libraries.
230 pub pre_link_args: Vec<String>,
231 /// Objects to link before all others, always found within the
233 pub pre_link_objects_exe: Vec<String>, // ... when linking an executable
234 pub pre_link_objects_dll: Vec<String>, // ... when linking a dylib
235 /// Linker arguments that are unconditionally passed after any
236 /// user-defined but before post_link_objects. Standard platform
237 /// libraries that should be always be linked to, usually go here.
238 pub late_link_args: Vec<String>,
239 /// Objects to link after all others, always found within the
241 pub post_link_objects: Vec<String>,
242 /// Linker arguments that are unconditionally passed *after* any
243 /// user-defined libraries.
244 pub post_link_args: Vec<String>,
246 /// Default CPU to pass to LLVM. Corresponds to `llc -mcpu=$cpu`. Defaults
249 /// Default target features to pass to LLVM. These features will *always* be
250 /// passed, and cannot be disabled even via `-C`. Corresponds to `llc
251 /// -mattr=$features`.
252 pub features: String,
253 /// Whether dynamic linking is available on this target. Defaults to false.
254 pub dynamic_linking: bool,
255 /// Whether executables are available on this target. iOS, for example, only allows static
256 /// libraries. Defaults to false.
257 pub executables: bool,
258 /// Relocation model to use in object file. Corresponds to `llc
259 /// -relocation-model=$relocation_model`. Defaults to "pic".
260 pub relocation_model: String,
261 /// Code model to use. Corresponds to `llc -code-model=$code_model`. Defaults to "default".
262 pub code_model: String,
263 /// Do not emit code that uses the "red zone", if the ABI has one. Defaults to false.
264 pub disable_redzone: bool,
265 /// Eliminate frame pointers from stack frames if possible. Defaults to true.
266 pub eliminate_frame_pointer: bool,
267 /// Emit each function in its own section. Defaults to true.
268 pub function_sections: bool,
269 /// String to prepend to the name of every dynamic library. Defaults to "lib".
270 pub dll_prefix: String,
271 /// String to append to the name of every dynamic library. Defaults to ".so".
272 pub dll_suffix: String,
273 /// String to append to the name of every executable.
274 pub exe_suffix: String,
275 /// String to prepend to the name of every static library. Defaults to "lib".
276 pub staticlib_prefix: String,
277 /// String to append to the name of every static library. Defaults to ".a".
278 pub staticlib_suffix: String,
279 /// OS family to use for conditional compilation. Valid options: "unix", "windows".
280 pub target_family: Option<String>,
281 /// Whether the target toolchain is like OSX's. Only useful for compiling against iOS/OS X, in
282 /// particular running dsymutil and some other stuff like `-dead_strip`. Defaults to false.
283 pub is_like_osx: bool,
284 /// Whether the target toolchain is like Solaris's.
285 /// Only useful for compiling against Illumos/Solaris,
286 /// as they have a different set of linker flags. Defaults to false.
287 pub is_like_solaris: bool,
288 /// Whether the target toolchain is like Windows'. Only useful for compiling against Windows,
289 /// only really used for figuring out how to find libraries, since Windows uses its own
290 /// library naming convention. Defaults to false.
291 pub is_like_windows: bool,
292 pub is_like_msvc: bool,
293 /// Whether the target toolchain is like Android's. Only useful for compiling against Android.
294 /// Defaults to false.
295 pub is_like_android: bool,
296 /// Whether the linker support GNU-like arguments such as -O. Defaults to false.
297 pub linker_is_gnu: bool,
298 /// The MinGW toolchain has a known issue that prevents it from correctly
299 /// handling COFF object files with more than 2^15 sections. Since each weak
300 /// symbol needs its own COMDAT section, weak linkage implies a large
301 /// number sections that easily exceeds the given limit for larger
302 /// codebases. Consequently we want a way to disallow weak linkage on some
304 pub allows_weak_linkage: bool,
305 /// Whether the linker support rpaths or not. Defaults to false.
307 /// Whether to disable linking to compiler-rt. Defaults to false, as LLVM
308 /// will emit references to the functions that compiler-rt provides.
309 pub no_compiler_rt: bool,
310 /// Whether to disable linking to the default libraries, typically corresponds
311 /// to `-nodefaultlibs`. Defaults to true.
312 pub no_default_libraries: bool,
313 /// Dynamically linked executables can be compiled as position independent
314 /// if the default relocation model of position independent code is not
315 /// changed. This is a requirement to take advantage of ASLR, as otherwise
316 /// the functions in the executable are not randomized and can be used
317 /// during an exploit of a vulnerability in any code.
318 pub position_independent_executables: bool,
319 /// Format that archives should be emitted in. This affects whether we use
320 /// LLVM to assemble an archive or fall back to the system linker, and
321 /// currently only "gnu" is used to fall into LLVM. Unknown strings cause
322 /// the system linker to be used.
323 pub archive_format: String,
324 /// Is asm!() allowed? Defaults to true.
326 /// Whether the target uses a custom unwind resumption routine.
327 /// By default LLVM lowers `resume` instructions into calls to `_Unwind_Resume`
328 /// defined in libgcc. If this option is enabled, the target must provide
329 /// `eh_unwind_resume` lang item.
330 pub custom_unwind_resume: bool,
332 /// Default crate for allocation symbols to link against
333 pub lib_allocation_crate: String,
334 pub exe_allocation_crate: String,
336 /// Flag indicating whether ELF TLS (e.g. #[thread_local]) is available for
338 pub has_elf_tls: bool,
339 // This is mainly for easy compatibility with emscripten.
340 // If we give emcc .o files that are actually .bc files it
342 pub obj_is_bitcode: bool,
344 /// Maximum integer size in bits that this target can perform atomic
346 pub max_atomic_width: u64,
349 impl Default for TargetOptions {
350 /// Create a set of "sane defaults" for any target. This is still
351 /// incomplete, and if used for compilation, will certainly not work.
352 fn default() -> TargetOptions {
355 linker: option_env!("CFG_DEFAULT_LINKER").unwrap_or("cc").to_string(),
356 ar: option_env!("CFG_DEFAULT_AR").unwrap_or("ar").to_string(),
357 pre_link_args: Vec::new(),
358 post_link_args: Vec::new(),
359 cpu: "generic".to_string(),
360 features: "".to_string(),
361 dynamic_linking: false,
363 relocation_model: "pic".to_string(),
364 code_model: "default".to_string(),
365 disable_redzone: false,
366 eliminate_frame_pointer: true,
367 function_sections: true,
368 dll_prefix: "lib".to_string(),
369 dll_suffix: ".so".to_string(),
370 exe_suffix: "".to_string(),
371 staticlib_prefix: "lib".to_string(),
372 staticlib_suffix: ".a".to_string(),
375 is_like_solaris: false,
376 is_like_windows: false,
377 is_like_android: false,
379 linker_is_gnu: false,
380 allows_weak_linkage: true,
382 no_compiler_rt: false,
383 no_default_libraries: true,
384 position_independent_executables: false,
385 pre_link_objects_exe: Vec::new(),
386 pre_link_objects_dll: Vec::new(),
387 post_link_objects: Vec::new(),
388 late_link_args: Vec::new(),
389 archive_format: "gnu".to_string(),
390 custom_unwind_resume: false,
391 lib_allocation_crate: "alloc_system".to_string(),
392 exe_allocation_crate: "alloc_system".to_string(),
395 obj_is_bitcode: false,
402 /// Given a function ABI, turn "System" into the correct ABI for this target.
403 pub fn adjust_abi(&self, abi: Abi) -> Abi {
406 if self.options.is_like_windows && self.arch == "x86" {
416 /// Load a target descriptor from a JSON object.
417 pub fn from_json(obj: Json) -> TargetResult {
418 // While ugly, this code must remain this way to retain
419 // compatibility with existing JSON fields and the internal
420 // expected naming of the Target and TargetOptions structs.
421 // To ensure compatibility is retained, the built-in targets
422 // are round-tripped through this code to catch cases where
423 // the JSON parser is not updated to match the structs.
425 let get_req_field = |name: &str| {
427 .map(|s| s.as_string())
428 .and_then(|os| os.map(|s| s.to_string())) {
429 Some(val) => Ok(val),
431 return Err(format!("Field {} in target specification is required", name))
436 let get_opt_field = |name: &str, default: &str| {
437 obj.find(name).and_then(|s| s.as_string())
438 .map(|s| s.to_string())
439 .unwrap_or(default.to_string())
442 let mut base = Target {
443 llvm_target: try!(get_req_field("llvm-target")),
444 target_endian: try!(get_req_field("target-endian")),
445 target_pointer_width: try!(get_req_field("target-pointer-width")),
446 data_layout: try!(get_req_field("data-layout")),
447 arch: try!(get_req_field("arch")),
448 target_os: try!(get_req_field("os")),
449 target_env: get_opt_field("env", ""),
450 target_vendor: get_opt_field("vendor", "unknown"),
451 options: Default::default(),
454 // Default max-atomic-width to target-pointer-width
455 base.options.max_atomic_width = base.target_pointer_width.parse().unwrap();
458 ($key_name:ident) => ( {
459 let name = (stringify!($key_name)).replace("_", "-");
460 obj.find(&name[..]).map(|o| o.as_string()
461 .map(|s| base.options.$key_name = s.to_string()));
463 ($key_name:ident, bool) => ( {
464 let name = (stringify!($key_name)).replace("_", "-");
466 .map(|o| o.as_boolean()
467 .map(|s| base.options.$key_name = s));
469 ($key_name:ident, u64) => ( {
470 let name = (stringify!($key_name)).replace("_", "-");
473 .map(|s| base.options.$key_name = s));
475 ($key_name:ident, list) => ( {
476 let name = (stringify!($key_name)).replace("_", "-");
477 obj.find(&name[..]).map(|o| o.as_array()
478 .map(|v| base.options.$key_name = v.iter()
479 .map(|a| a.as_string().unwrap().to_string()).collect()
483 ($key_name:ident, optional) => ( {
484 let name = (stringify!($key_name)).replace("_", "-");
485 if let Some(o) = obj.find(&name[..]) {
486 base.options.$key_name = o
488 .map(|s| s.to_string() );
493 key!(is_builtin, bool);
496 key!(pre_link_args, list);
497 key!(pre_link_objects_exe, list);
498 key!(pre_link_objects_dll, list);
499 key!(late_link_args, list);
500 key!(post_link_objects, list);
501 key!(post_link_args, list);
504 key!(dynamic_linking, bool);
505 key!(executables, bool);
506 key!(relocation_model);
508 key!(disable_redzone, bool);
509 key!(eliminate_frame_pointer, bool);
510 key!(function_sections, bool);
514 key!(staticlib_prefix);
515 key!(staticlib_suffix);
516 key!(target_family, optional);
517 key!(is_like_osx, bool);
518 key!(is_like_solaris, bool);
519 key!(is_like_windows, bool);
520 key!(is_like_msvc, bool);
521 key!(is_like_android, bool);
522 key!(linker_is_gnu, bool);
523 key!(allows_weak_linkage, bool);
524 key!(has_rpath, bool);
525 key!(no_compiler_rt, bool);
526 key!(no_default_libraries, bool);
527 key!(position_independent_executables, bool);
528 key!(archive_format);
529 key!(allow_asm, bool);
530 key!(custom_unwind_resume, bool);
531 key!(lib_allocation_crate);
532 key!(exe_allocation_crate);
533 key!(has_elf_tls, bool);
534 key!(obj_is_bitcode, bool);
535 key!(max_atomic_width, u64);
540 /// Search RUST_TARGET_PATH for a JSON file specifying the given target
541 /// triple. Note that it could also just be a bare filename already, so also
542 /// check for that. If one of the hardcoded targets we know about, just
543 /// return it directly.
545 /// The error string could come from any of the APIs called, including
546 /// filesystem access and JSON decoding.
547 pub fn search(target: &str) -> Result<Target, String> {
549 use std::ffi::OsString;
551 use std::path::{Path, PathBuf};
554 fn load_file(path: &Path) -> Result<Target, String> {
555 let mut f = File::open(path).map_err(|e| e.to_string())?;
556 let mut contents = Vec::new();
557 f.read_to_end(&mut contents).map_err(|e| e.to_string())?;
558 let obj = json::from_reader(&mut &contents[..])
559 .map_err(|e| e.to_string())?;
560 Target::from_json(obj)
563 if let Ok(t) = load_specific(target) {
567 let path = Path::new(target);
570 return load_file(&path);
574 let mut target = target.to_string();
575 target.push_str(".json");
576 PathBuf::from(target)
579 let target_path = env::var_os("RUST_TARGET_PATH")
580 .unwrap_or(OsString::new());
582 // FIXME 16351: add a sane default search path?
584 for dir in env::split_paths(&target_path) {
585 let p = dir.join(&path);
587 return load_file(&p);
591 Err(format!("Could not find specification for target {:?}", target))
595 impl ToJson for Target {
596 fn to_json(&self) -> Json {
597 let mut d = BTreeMap::new();
598 let default: TargetOptions = Default::default();
600 macro_rules! target_val {
602 let name = (stringify!($attr)).replace("_", "-");
603 d.insert(name.to_string(), self.$attr.to_json());
605 ($attr:ident, $key_name:expr) => ( {
606 let name = $key_name;
607 d.insert(name.to_string(), self.$attr.to_json());
611 macro_rules! target_option_val {
613 let name = (stringify!($attr)).replace("_", "-");
614 if default.$attr != self.options.$attr {
615 d.insert(name.to_string(), self.options.$attr.to_json());
618 ($attr:ident, $key_name:expr) => ( {
619 let name = $key_name;
620 if default.$attr != self.options.$attr {
621 d.insert(name.to_string(), self.options.$attr.to_json());
626 target_val!(llvm_target);
627 target_val!(target_endian);
628 target_val!(target_pointer_width);
630 target_val!(target_os, "os");
631 target_val!(target_env, "env");
632 target_val!(target_vendor, "vendor");
634 target_val!(data_layout);
636 target_option_val!(is_builtin);
637 target_option_val!(linker);
638 target_option_val!(ar);
639 target_option_val!(pre_link_args);
640 target_option_val!(pre_link_objects_exe);
641 target_option_val!(pre_link_objects_dll);
642 target_option_val!(late_link_args);
643 target_option_val!(post_link_objects);
644 target_option_val!(post_link_args);
645 target_option_val!(cpu);
646 target_option_val!(features);
647 target_option_val!(dynamic_linking);
648 target_option_val!(executables);
649 target_option_val!(relocation_model);
650 target_option_val!(code_model);
651 target_option_val!(disable_redzone);
652 target_option_val!(eliminate_frame_pointer);
653 target_option_val!(function_sections);
654 target_option_val!(dll_prefix);
655 target_option_val!(dll_suffix);
656 target_option_val!(exe_suffix);
657 target_option_val!(staticlib_prefix);
658 target_option_val!(staticlib_suffix);
659 target_option_val!(target_family);
660 target_option_val!(is_like_osx);
661 target_option_val!(is_like_solaris);
662 target_option_val!(is_like_windows);
663 target_option_val!(is_like_msvc);
664 target_option_val!(is_like_android);
665 target_option_val!(linker_is_gnu);
666 target_option_val!(allows_weak_linkage);
667 target_option_val!(has_rpath);
668 target_option_val!(no_compiler_rt);
669 target_option_val!(no_default_libraries);
670 target_option_val!(position_independent_executables);
671 target_option_val!(archive_format);
672 target_option_val!(allow_asm);
673 target_option_val!(custom_unwind_resume);
674 target_option_val!(lib_allocation_crate);
675 target_option_val!(exe_allocation_crate);
676 target_option_val!(has_elf_tls);
677 target_option_val!(obj_is_bitcode);
678 target_option_val!(max_atomic_width);
684 fn maybe_jemalloc() -> String {
685 if cfg!(feature = "jemalloc") {
686 "alloc_jemalloc".to_string()
688 "alloc_system".to_string()