Add no_std support to bevy_log

Shatur · Shatur · commit c39807d48bfe · 2025-08-12T21:43:44.000+03:00
Currently requires a new release of `tracing-subscriber`. Once released,
2 lines needs to be uncommented in `Cargo.toml`, see `TODO`.
diff --git a/Cargo.toml b/Cargo.toml
@@ -145,7 +145,6 @@ default = [
   "bevy_gizmos",
   "bevy_gltf",
   "bevy_input_focus",
-  "bevy_log",
   "bevy_mesh_picking_backend",
   "bevy_pbr",
   "bevy_picking",
@@ -309,9 +308,6 @@ bevy_dev_tools = ["bevy_internal/bevy_dev_tools"]
 # Enable the Bevy Remote Protocol
 bevy_remote = ["bevy_internal/bevy_remote"]
 
-# Enable integration with `tracing` and `log`
-bevy_log = ["bevy_internal/bevy_log"]
-
 # Enable input focus subsystem
 bevy_input_focus = ["bevy_internal/bevy_input_focus"]
 
@@ -1710,7 +1706,6 @@ wasm = true
 name = "headless"
 path = "examples/app/headless.rs"
 doc-scrape-examples = true
-required-features = ["bevy_log"]
 
 [package.metadata.example.headless]
 name = "Headless"
diff --git a/crates/bevy_animation/Cargo.toml b/crates/bevy_animation/Cargo.toml
@@ -45,6 +45,18 @@ tracing = { version = "0.1", default-features = false, features = ["std"] }
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 # TODO: Assuming all wasm builds are for the browser. Require `no_std` support to break assumption.
 uuid = { version = "1.13.1", default-features = false, features = ["js"] }
+bevy_log = { path = "../bevy_log", version = "0.17.0-dev", default-features = false, features = [
+  "web",
+] }
+bevy_app = { path = "../bevy_app", version = "0.17.0-dev", default-features = false, features = [
+  "web",
+] }
+bevy_platform = { path = "../bevy_platform", version = "0.17.0-dev", default-features = false, features = [
+  "web",
+] }
+bevy_reflect = { path = "../bevy_reflect", version = "0.17.0-dev", default-features = false, features = [
+  "web",
+] }
 
 [lints]
 workspace = true
diff --git a/crates/bevy_dylib/src/lib.rs b/crates/bevy_dylib/src/lib.rs
@@ -53,6 +53,8 @@
 //! use bevy_dylib;
 //! ```
 
+#![no_std]
+
 // Force linking of the main bevy crate
 #[expect(
     unused_imports,
diff --git a/crates/bevy_gltf/Cargo.toml b/crates/bevy_gltf/Cargo.toml
@@ -66,6 +66,21 @@ smallvec = { version = "1", default-features = false }
 tracing = { version = "0.1", default-features = false, features = ["std"] }
 bevy_log = { path = "../bevy_log", version = "0.17.0-dev" }
 
+[target.'cfg(target_arch = "wasm32")'.dependencies]
+# TODO: Assuming all wasm builds are for the browser. Require `no_std` support to break assumption.
+bevy_log = { path = "../bevy_log", version = "0.17.0-dev", default-features = false, features = [
+  "web",
+] }
+bevy_app = { path = "../bevy_app", version = "0.17.0-dev", default-features = false, features = [
+  "web",
+] }
+bevy_platform = { path = "../bevy_platform", version = "0.17.0-dev", default-features = false, features = [
+  "web",
+] }
+bevy_reflect = { path = "../bevy_reflect", version = "0.17.0-dev", default-features = false, features = [
+  "web",
+] }
+
 [lints]
 workspace = true
 
diff --git a/crates/bevy_internal/Cargo.toml b/crates/bevy_internal/Cargo.toml
@@ -332,6 +332,7 @@ std = [
   "bevy_ecs/std",
   "bevy_input/std",
   "bevy_input_focus?/std",
+  "bevy_log/std",
   "bevy_math/std",
   "bevy_platform/std",
   "bevy_reflect/std",
@@ -348,6 +349,7 @@ critical-section = [
   "bevy_app/critical-section",
   "bevy_diagnostic/critical-section",
   "bevy_ecs/critical-section",
+  "bevy_log/critical-section",
   "bevy_input/critical-section",
   "bevy_input_focus?/critical-section",
   "bevy_platform/critical-section",
@@ -377,7 +379,7 @@ async_executor = [
 
 # Enables use of browser APIs.
 # Note this is currently only applicable on `wasm32` architectures.
-web = ["bevy_app/web", "bevy_platform/web", "bevy_reflect/web"]
+web = ["bevy_app/web", "bevy_log/web", "bevy_platform/web", "bevy_reflect/web"]
 
 hotpatching = ["bevy_app/hotpatching", "bevy_ecs/hotpatching"]
 
@@ -400,6 +402,7 @@ bevy_ecs = { path = "../bevy_ecs", version = "0.17.0-dev", default-features = fa
 bevy_input = { path = "../bevy_input", version = "0.17.0-dev", default-features = false, features = [
   "bevy_reflect",
 ] }
+bevy_log = { path = "../bevy_log", version = "0.17.0-dev", default-features = false }
 bevy_math = { path = "../bevy_math", version = "0.17.0-dev", default-features = false, features = [
   "bevy_reflect",
   "nostd-libm",
@@ -421,9 +424,6 @@ bevy_transform = { path = "../bevy_transform", version = "0.17.0-dev", default-f
 bevy_utils = { path = "../bevy_utils", version = "0.17.0-dev", default-features = false }
 bevy_tasks = { path = "../bevy_tasks", version = "0.17.0-dev", default-features = false }
 
-# bevy (std required)
-bevy_log = { path = "../bevy_log", version = "0.17.0-dev", optional = true }
-
 # bevy (optional)
 bevy_a11y = { path = "../bevy_a11y", optional = true, version = "0.17.0-dev", features = [
   "bevy_reflect",
diff --git a/crates/bevy_internal/src/default_plugins.rs b/crates/bevy_internal/src/default_plugins.rs
@@ -4,7 +4,6 @@ plugin_group! {
     /// This plugin group will add all the default plugins for a *Bevy* application:
     pub struct DefaultPlugins {
         bevy_app:::PanicHandlerPlugin,
-        #[cfg(feature = "bevy_log")]
         bevy_log:::LogPlugin,
         bevy_app:::TaskPoolPlugin,
         bevy_diagnostic:::FrameCountPlugin,
diff --git a/crates/bevy_internal/src/lib.rs b/crates/bevy_internal/src/lib.rs
@@ -54,7 +54,6 @@ pub use bevy_input as input;
 pub use bevy_input_focus as input_focus;
 #[cfg(feature = "bevy_light")]
 pub use bevy_light as light;
-#[cfg(feature = "bevy_log")]
 pub use bevy_log as log;
 pub use bevy_math as math;
 #[cfg(feature = "bevy_mesh")]
diff --git a/crates/bevy_internal/src/prelude.rs b/crates/bevy_internal/src/prelude.rs
@@ -1,14 +1,10 @@
 #[doc(hidden)]
 pub use crate::{
-    app::prelude::*, ecs::prelude::*, input::prelude::*, math::prelude::*, platform::prelude::*,
-    reflect::prelude::*, time::prelude::*, transform::prelude::*, utils::prelude::*,
-    DefaultPlugins, MinimalPlugins,
+    app::prelude::*, ecs::prelude::*, input::prelude::*, log::prelude::*, math::prelude::*,
+    platform::prelude::*, reflect::prelude::*, time::prelude::*, transform::prelude::*,
+    utils::prelude::*, DefaultPlugins, MinimalPlugins,
 };
 
-#[doc(hidden)]
-#[cfg(feature = "bevy_log")]
-pub use crate::log::prelude::*;
-
 #[doc(hidden)]
 #[cfg(feature = "bevy_window")]
 pub use crate::window::prelude::*;
diff --git a/crates/bevy_log/Cargo.toml b/crates/bevy_log/Cargo.toml
@@ -9,25 +9,55 @@ license = "MIT OR Apache-2.0"
 keywords = ["bevy"]
 
 [features]
-trace = ["tracing-error"]
-trace_tracy_memory = ["dep:tracy-client"]
+default = ["std"]
+trace = ["std", "dep:tracing-error"]
+trace_tracy_memory = ["std", "dep:tracy-client"]
+
+# Platform Compatibility
+
+# Allows access to the `std` crate. Enabling this feature will prevent compilation
+# on `no_std` targets, but provides access to certain additional features on
+# supported platforms.
+std = [
+  "bevy_app/std",
+  "bevy_utils/std",
+  "bevy_ecs/std",
+  "tracing/std",
+  "tracing-subscriber/std",
+  "tracing-log/std",
+]
+
+## `critical-section` provides the building blocks for synchronization primitives
+## on all platforms, including `no_std`.
+critical-section = [
+  # TODO: wait for `tracing-subscriber` release
+  # "tracing-subscriber/critical-section"
+]
+
+# Enables use of browser APIs.
+# Note this is currently only applicable on `wasm32` architectures.
+web = ["bevy_app/web", "dep:tracing-wasm"]
 
 [dependencies]
 # bevy
-bevy_app = { path = "../bevy_app", version = "0.17.0-dev" }
-bevy_utils = { path = "../bevy_utils", version = "0.17.0-dev" }
-bevy_platform = { path = "../bevy_platform", version = "0.17.0-dev" }
-bevy_ecs = { path = "../bevy_ecs", version = "0.17.0-dev" }
+bevy_app = { path = "../bevy_app", version = "0.17.0-dev", default-features = false }
+bevy_utils = { path = "../bevy_utils", version = "0.17.0-dev", default-features = false }
+bevy_platform = { path = "../bevy_platform", version = "0.17.0-dev", default-features = false }
+bevy_ecs = { path = "../bevy_ecs", version = "0.17.0-dev", default-features = false }
 
 # other
-tracing-subscriber = { version = "0.3.1", features = [
+tracing-subscriber = { version = "0.3.1", default-features = false, features = [
   "registry",
   "env-filter",
+  "fmt",
+  "tracing-log",
 ] }
 tracing-chrome = { version = "0.7.0", optional = true }
-tracing-log = "0.2.0"
+tracing-log = { version = "0.2.0", default-features = false, features = [
+  "log-tracer",
+] }
 tracing-error = { version = "0.2.0", optional = true }
-tracing = { version = "0.1", default-features = false, features = ["std"] }
+tracing = { version = "0.1", default-features = false }
 
 # Tracy dependency compatibility table:
 # https://github.com/nagisa/rust_tracy_client
@@ -38,15 +68,17 @@ tracy-client = { version = "0.18.0", optional = true }
 android_log-sys = "0.3.0"
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
-tracing-wasm = "0.2.1"
-# TODO: Assuming all wasm builds are for the browser. Require `no_std` support to break assumption.
-bevy_app = { path = "../bevy_app", version = "0.17.0-dev", default-features = false, features = [
-  "web",
-] }
+tracing-wasm = { version = "0.2.1", optional = true }
 
 [target.'cfg(target_os = "ios")'.dependencies]
 tracing-oslog = "0.3"
 
+[target.'cfg(not(all(target_has_atomic = "8", target_has_atomic = "16", target_has_atomic = "32", target_has_atomic = "64", target_has_atomic = "ptr")))'.dependencies]
+tracing-subscriber = { version = "0.3.1", default-features = false, features = [
+  # TODO: wait for `tracing-subscriber` release
+  # "portable-atomic",
+] }
+
 [lints]
 workspace = true
 
diff --git a/crates/bevy_log/src/android_tracing.rs b/crates/bevy_log/src/android_tracing.rs
@@ -1,4 +1,4 @@
-use alloc::ffi::CString;
+use alloc::{ffi::CString, format, string::String, vec::Vec};
 use core::fmt::{Debug, Write};
 use tracing::{
     field::Field,
diff --git a/crates/bevy_log/src/lib.rs b/crates/bevy_log/src/lib.rs
@@ -15,10 +15,11 @@
 //!
 //! For more fine-tuned control over logging behavior, set up the [`LogPlugin`] or
 //! `DefaultPlugins` during app initialization.
+#![no_std]
 
 extern crate alloc;
-
-use core::error::Error;
+#[cfg(feature = "std")]
+extern crate std;
 
 #[cfg(target_os = "android")]
 mod android_tracing;
@@ -52,6 +53,15 @@ pub use tracing::{
 };
 pub use tracing_subscriber;
 
+use alloc::{
+    boxed::Box,
+    format,
+    string::{String, ToString},
+};
+use core::error::Error;
+#[cfg(feature = "std")]
+use std::eprintln;
+
 use bevy_app::{App, Plugin};
 use tracing_log::LogTracer;
 use tracing_subscriber::{
@@ -312,9 +322,10 @@ impl Plugin for LogPlugin {
                 _ = from_env_error
                     .source()
                     .and_then(|source| source.downcast_ref::<ParseError>())
-                    .map(|parse_err| {
+                    .inspect(|_parse_err| {
                         // we cannot use the `error!` macro here because the logger is not ready yet.
-                        eprintln!("LogPlugin failed to parse filter from env: {parse_err}");
+                        #[cfg(feature = "std")]
+                        eprintln!("LogPlugin failed to parse filter from env: {_parse_err}");
                     });
 
                 Ok::<EnvFilter, FromEnvError>(EnvFilter::builder().parse_lossy(&default_filter))
@@ -358,6 +369,7 @@ impl Plugin for LogPlugin {
             #[cfg(feature = "tracing-tracy")]
             let tracy_layer = tracing_tracy::TracyLayer::default();
 
+            #[cfg(feature = "std")]
             let fmt_layer = (self.fmt_layer)(app).unwrap_or_else(|| {
                 // note: the implementation of `Default` reads from the env var NO_COLOR
                 // to decide whether to use ANSI color codes, which is common convention
@@ -373,6 +385,7 @@ impl Plugin for LogPlugin {
                     meta.fields().field("tracy.frame_mark").is_none()
                 }));
 
+            #[cfg(any(feature = "std", feature = "tracing-tracy"))]
             let subscriber = subscriber.with(fmt_layer);
 
             #[cfg(feature = "tracing-chrome")]
diff --git a/crates/bevy_text/Cargo.toml b/crates/bevy_text/Cargo.toml
@@ -41,6 +41,21 @@ smallvec = { version = "1", default-features = false }
 sys-locale = "0.3.0"
 tracing = { version = "0.1", default-features = false, features = ["std"] }
 
+[target.'cfg(target_arch = "wasm32")'.dependencies]
+# TODO: Assuming all wasm builds are for the browser. Require `no_std` support to break assumption.
+bevy_log = { path = "../bevy_log", version = "0.17.0-dev", default-features = false, features = [
+  "web",
+] }
+bevy_app = { path = "../bevy_app", version = "0.17.0-dev", default-features = false, features = [
+  "web",
+] }
+bevy_platform = { path = "../bevy_platform", version = "0.17.0-dev", default-features = false, features = [
+  "web",
+] }
+bevy_reflect = { path = "../bevy_reflect", version = "0.17.0-dev", default-features = false, features = [
+  "web",
+] }
+
 [dev-dependencies]
 approx = "0.5.1"
 
diff --git a/crates/bevy_transform/Cargo.toml b/crates/bevy_transform/Cargo.toml
@@ -41,7 +41,7 @@ default = ["std", "bevy-support", "bevy_reflect", "async_executor"]
 ## systems for transform propagation and more.
 ## This exists because it allows opting out of all of this, leaving only a bare-bones transform struct,
 ## which enables users to depend on that without needing the larger Bevy dependency tree.
-bevy-support = ["alloc", "dep:bevy_app", "dep:bevy_ecs"]
+bevy-support = ["alloc", "dep:bevy_app", "dep:bevy_log", "dep:bevy_ecs"]
 
 ## Adds serialization support through `serde`.
 serialize = ["dep:serde", "bevy_math/serialize"]
@@ -69,7 +69,7 @@ async_executor = ["std", "bevy_tasks/async_executor"]
 std = [
   "alloc",
   "bevy_app?/std",
-  "bevy_log",
+  "bevy_log?/std",
   "bevy_ecs?/std",
   "bevy_math/std",
   "bevy_reflect?/std",
diff --git a/crates/bevy_transform/src/systems.rs b/crates/bevy_transform/src/systems.rs
@@ -332,7 +332,6 @@ mod parallel {
     /// children to the queue once it has propagated their [`GlobalTransform`].
     #[inline]
     fn propagation_worker(queue: &WorkQueue, nodes: &NodeQuery) {
-        #[cfg(feature = "std")]
         let _span = bevy_log::info_span!("transform propagation worker").entered();
 
         let mut outbox = queue.local_queue.borrow_local_mut();
diff --git a/crates/bevy_winit/Cargo.toml b/crates/bevy_winit/Cargo.toml
@@ -85,6 +85,9 @@ bevy_platform = { path = "../bevy_platform", version = "0.17.0-dev", default-fea
 bevy_reflect = { path = "../bevy_reflect", version = "0.17.0-dev", default-features = false, features = [
   "web",
 ] }
+bevy_log = { path = "../bevy_log", version = "0.17.0-dev", default-features = false, features = [
+  "web",
+] }
 
 [lints]
 workspace = true
diff --git a/docs/cargo_features.md b/docs/cargo_features.md
@@ -26,7 +26,6 @@ The default feature set enables most of the expected features of a game engine,
 |bevy_gizmos|Adds support for rendering gizmos|
 |bevy_gltf|[glTF](https://www.khronos.org/gltf/) support|
 |bevy_input_focus|Enable input focus subsystem|
-|bevy_log|Enable integration with `tracing` and `log`|
 |bevy_mesh_picking_backend|Provides an implementation for picking meshes|
 |bevy_pbr|Adds PBR rendering|
 |bevy_picking|Provides picking functionality|

Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-use alloc::ffi::CString;`
	`1`	`+use alloc::{ffi::CString, format, string::String, vec::Vec};`
`2`	`2`	`use core::fmt::{Debug, Write};`
`3`	`3`	`use tracing::{`
`4`	`4`	`field::Field,`