Don't automatically enable std and alloc features of dependencies

Unless it's currently required.

Part of #656.

crates/block2/Cargo.toml

@@ -22,8 +22,8 @@ workspace = true
 default = ["std"]
 
 # Currently not possible to turn off, put here for forwards compatibility.
-std = ["alloc", "objc2/std"]
-alloc = ["objc2/alloc"]
+std = ["alloc"]
+alloc = []
 
 # Deprecated; this is the default on Apple platforms, and not applicable on other platforms.
 apple = []
@@ -48,12 +48,12 @@ unstable-objfw = []
 unstable-private = []
 
 [dependencies]
-objc2 = { path = "../objc2", version = "0.5.2", default-features = false }
+objc2 = { path = "../objc2", version = "0.5.2", default-features = false, features = ["std"] }
 
 [dev-dependencies.objc2-foundation]
 path = "../../framework-crates/objc2-foundation"
 default-features = false
-features = ["NSError"]
+features = ["std", "NSError"]
 
 [package.metadata.docs.rs]
 default-target = "aarch64-apple-darwin"

crates/block2/src/lib.rs

@@ -304,12 +304,13 @@
 #![cfg_attr(docsrs, feature(doc_auto_cfg, doc_cfg_hide))]
 #![cfg_attr(docsrs, doc(cfg_hide(doc)))]
 
+#[cfg(not(feature = "alloc"))]
+compile_error!("The `alloc` feature currently must be enabled.");
+
 extern crate alloc;
+#[cfg(feature = "std")]
 extern crate std;
 
-#[cfg(not(feature = "std"))]
-compile_error!("The `std` feature currently must be enabled.");
-
 #[cfg(all(
     not(docsrs),
     not(any(

crates/block2/src/rc_block.rs

@@ -154,7 +154,7 @@ impl<F: ?Sized> RcBlock<F> {
     /// # Example
     ///
     /// ```
-    /// # use std::ffi::CStr;
+    /// # use core::ffi::CStr;
     /// # use block2::{Block, ManualBlockEncoding, RcBlock};
     /// # use objc2_foundation::NSError;
     /// #
@@ -173,7 +173,7 @@ impl<F: ?Sized> RcBlock<F> {
     /// let my_block = RcBlock::with_encoding::<_, _, _, MyBlockEncoding>(|_err: *mut NSError| {
     ///     42i32
     /// });
-    /// assert_eq!(my_block.call((std::ptr::null_mut(),)), 42);
+    /// assert_eq!(my_block.call((core::ptr::null_mut(),)), 42);
     /// ```
     #[inline]
     pub fn with_encoding<'f, A, R, Closure, E>(closure: Closure) -> Self

crates/block2/src/stack.rs

@@ -205,7 +205,7 @@ where
     /// # Example
     ///
     /// ```
-    /// # use std::ffi::CStr;
+    /// # use core::ffi::CStr;
     /// # use block2::{Block, ManualBlockEncoding, StackBlock};
     /// # use objc2_foundation::NSError;
     /// #
@@ -224,7 +224,7 @@ where
     /// let my_block = StackBlock::with_encoding::<MyBlockEncoding>(|_err: *mut NSError| {
     ///     42i32
     /// });
-    /// assert_eq!(my_block.call((std::ptr::null_mut(),)), 42);
+    /// assert_eq!(my_block.call((core::ptr::null_mut(),)), 42);
     /// ```
     #[inline]
     pub fn with_encoding<E>(closure: Closure) -> Self

crates/block2/src/traits.rs

@@ -1,8 +1,7 @@
+use core::ffi::CStr;
 use core::marker::PhantomData;
 use core::mem;
 use core::ptr;
-// TODO: use `core` when the MSRV is at least 1.64.
-use std::ffi::CStr;
 
 use objc2::encode::EncodeArguments;
 use objc2::encode::{EncodeArgument, EncodeReturn};
@@ -347,7 +346,7 @@ mod tests {
                 unsafe { CStr::from_bytes_with_nul_unchecked(b"C12@?0i4f8\0") };
         }
         // HACK: use `identity` in order to circumvent a Clippy warning.
-        assert!(!std::convert::identity(UserSpecified::<Enc1>::IS_NONE));
+        assert!(!core::convert::identity(UserSpecified::<Enc1>::IS_NONE));
 
         // No input + no output case.
         struct Enc2;
@@ -361,7 +360,7 @@ mod tests {
             const ENCODING_CSTR: &'static CStr =
                 unsafe { CStr::from_bytes_with_nul_unchecked(b"v4@?0\0") };
         }
-        assert!(!std::convert::identity(UserSpecified::<Enc2>::IS_NONE));
+        assert!(!core::convert::identity(UserSpecified::<Enc2>::IS_NONE));
 
         // Ensure we don't rely on the encoding string's emptiness.
         struct Enc3;
@@ -371,14 +370,14 @@ mod tests {
             const ENCODING_CSTR: &'static CStr =
                 unsafe { CStr::from_bytes_with_nul_unchecked(b"\0") };
         }
-        assert!(!std::convert::identity(UserSpecified::<Enc3>::IS_NONE));
+        assert!(!core::convert::identity(UserSpecified::<Enc3>::IS_NONE));
 
         // Only `NoBlockEncoding` should be `IS_NONE`.
-        assert!(std::convert::identity(NoBlockEncoding::<(), ()>::IS_NONE));
-        assert!(std::convert::identity(
+        assert!(core::convert::identity(NoBlockEncoding::<(), ()>::IS_NONE));
+        assert!(core::convert::identity(
             NoBlockEncoding::<(i32, f32), u8>::IS_NONE
         ));
-        assert!(std::convert::identity(
+        assert!(core::convert::identity(
             NoBlockEncoding::<(*const u8,), *const c_char>::IS_NONE
         ));
     }

crates/dispatch2/CHANGELOG.md

@@ -50,6 +50,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
   crate.
 - Added `Once`, a wrapper over `dispatch_once_f` which works similarly to
   `std::sync::Once`.
+- Added `#![no_std]` support
 
 ### Changed
 - Moved to the `objc2` project.

crates/dispatch2/Cargo.toml

@@ -18,9 +18,9 @@ workspace = true
 
 [dependencies]
 bitflags = { version = "2.5.0", default-features = false }
-block2 = { path = "../block2", version = "0.5.1", default-features = false, optional = true }
+block2 = { path = "../block2", version = "0.5.1", default-features = false, optional = true, features = ["alloc"] }
 libc = { version = "0.2.80", default-features = false, optional = true }
-objc2 = { path = "../objc2", version = "0.5.2", default-features = false, optional = true }
+objc2 = { path = "../objc2", version = "0.5.2", default-features = false, optional = true, features = ["std"] }
 
 [package.metadata.docs.rs]
 default-target = "aarch64-apple-darwin"
@@ -39,10 +39,8 @@ targets = [
 
 [features]
 default = ["std"]
-
-# Currently not possible to turn off, put here for forwards compatibility.
-std = ["alloc", "bitflags/std", "block2?/std", "libc?/std", "objc2?/std"]
-alloc = ["block2?/alloc", "objc2?/alloc"]
+std = ["alloc", "bitflags/std"]
+alloc = []
 block2 = ["dep:block2"]
 libc = ["dep:libc"]
 objc2 = ["dep:objc2"]

crates/header-translator/src/default_cargo.toml

@@ -26,7 +26,5 @@ targets = [
 
 [features]
 default = ["std"]
-
-# Currently not possible to turn off, put here for forwards compatibility.
 std = ["alloc"]
 alloc = []

crates/header-translator/src/library.rs

@@ -116,6 +116,17 @@ impl Library {
             }
         }
 
+        for (krate, (_, _, krate_features)) in &mut dependencies {
+            // std is currently required for objc2
+            if *krate == "objc2" {
+                krate_features.insert("std".into());
+            }
+            // alloc is currently required for these crates
+            if matches!(*krate, "block2" | "dispatch2" | "objc2-foundation") {
+                krate_features.insert("alloc".into());
+            }
+        }
+
         dependencies
     }
 
@@ -273,6 +284,10 @@ see that for related crates.", self.data.krate)?;
                 (false, false) => format!("../{krate}"),
             };
             let mut table = match *krate {
+                "dispatch2" => InlineTable::from_iter([
+                    ("path", Value::from(path)),
+                    ("version", Value::from("0.1.0")),
+                ]),
                 "objc2" => InlineTable::from_iter([
                     ("path", Value::from(path)),
                     ("version", Value::from("0.5.2")),
@@ -327,19 +342,15 @@ see that for related crates.", self.data.krate)?;
                 .entry(krate)
                 .or_insert(Item::Value(Value::InlineTable(table)));
 
-            cargo_toml["features"]["std"]
-                .as_array_mut()
-                .unwrap()
-                .push(Value::from(format!(
-                    "{krate}{}/std",
-                    if *required { "" } else { "?" },
-                )));
-            if *krate != "bitflags" && *krate != "libc" {
-                cargo_toml["features"]["alloc"]
+            // Bitflags is more of an "internal" dependency, just like
+            // objc2-encode is mostly an internal dependency to objc2, so it's
+            // fine to special-case std for that here.
+            if *krate == "bitflags" {
+                cargo_toml["features"]["std"]
                     .as_array_mut()
                     .unwrap()
                     .push(Value::from(format!(
-                        "{krate}{}/alloc",
+                        "{krate}{}/std",
                         if *required { "" } else { "?" },
                     )));
             }

crates/objc2-encode/src/lib.rs

@@ -45,12 +45,10 @@
 #[cfg(not(feature = "alloc"))]
 compile_error!("the `alloc` feature currently must be enabled");
 
+extern crate alloc;
 #[cfg(any(feature = "std", doc))]
 extern crate std;
 
-#[cfg(any(feature = "alloc", test))]
-extern crate alloc;
-
 mod encoding;
 mod encoding_box;
 mod helper;

crates/objc2/Cargo.toml

@@ -25,8 +25,8 @@ workspace = true
 default = ["std"]
 
 # Currently not possible to turn off, put here for forwards compatibility.
-std = ["alloc", "objc2-encode/std", "block2/std", "objc2-foundation/std", "objc2-exception-helper?/std"]
-alloc = ["objc2-encode/alloc", "block2/alloc", "objc2-foundation/alloc", "objc2-exception-helper?/alloc"]
+std = ["alloc", "objc2-encode/std"]
+alloc = ["objc2-encode/alloc"]
 
 # Enables `objc2::exception::throw` and `objc2::exception::catch`
 exception = ["dep:objc2-exception-helper"]
@@ -125,11 +125,12 @@ objc2-exception-helper = { path = "../objc2-exception-helper", version = "0.1.0"
 iai = { version = "0.1", git = "https://github.com/madsmtm/iai", branch = "callgrind" }
 static_assertions = "1.1.0"
 memoffset = "0.9.0"
-block2 = { path = "../block2", default-features = false }
+block2 = { path = "../block2" }
 objc2-core-foundation = { path = "../../framework-crates/objc2-core-foundation", default-features = false, features = [
     "CFCGTypes",
 ] }
 objc2-foundation = { path = "../../framework-crates/objc2-foundation", default-features = false, features = [
+    "std",
     "NSArray",
     "NSDate",
     "NSDictionary",

crates/objc2/src/topics/about_generated/CHANGELOG.md

@@ -105,6 +105,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 * **BREAKING**: The feature flag guarding `SCSensitivityAnalysis` changed.
 * **BREAKING**: `-[NSSavePanel beginSheetForDirectory:file:modalForWindow:modalDelegate:didEndSelector:contextInfo:]`
   now takes an optional value as the file path.
+* **BREAKING**: No longer automatically enable `std` and `alloc` features of
+  dependencies. If you want a certain framework crate to use `std` or `alloc`
+  features, you cannot rely on a higher-level crate to enable that for you.
 
 ### Deprecated
 * Moved `MainThreadMarker` from `objc2-foundation` to `objc2`.

crates/test-assembly/crates/test_define_class/Cargo.toml

@@ -8,22 +8,22 @@ publish = false
 path = "lib.rs"
 
 [dependencies]
-objc2 = { path = "../../../objc2", optional = true }
-objc2-foundation = { path = "../../../../framework-crates/objc2-foundation", optional = true }
+objc2 = { path = "../../../objc2" }
+objc2-foundation = { path = "../../../../framework-crates/objc2-foundation" }
 
 [features]
-default = ["all", "objc2", "objc2-foundation"]
+default = ["all"]
 # Runtime
-gnustep-1-7 = ["objc2?/gnustep-1-7", "objc2-foundation?/gnustep-1-7"]
-gnustep-1-8 = ["gnustep-1-7", "objc2?/gnustep-1-8", "objc2-foundation?/gnustep-1-8"]
-gnustep-1-9 = ["gnustep-1-8", "objc2?/gnustep-1-9", "objc2-foundation?/gnustep-1-9"]
-gnustep-2-0 = ["gnustep-1-9", "objc2?/gnustep-2-0", "objc2-foundation?/gnustep-2-0"]
-gnustep-2-1 = ["gnustep-2-0", "objc2?/gnustep-2-1", "objc2-foundation?/gnustep-2-1"]
+gnustep-1-7 = ["objc2/gnustep-1-7", "objc2-foundation/gnustep-1-7"]
+gnustep-1-8 = ["gnustep-1-7", "objc2/gnustep-1-8", "objc2-foundation/gnustep-1-8"]
+gnustep-1-9 = ["gnustep-1-8", "objc2/gnustep-1-9", "objc2-foundation/gnustep-1-9"]
+gnustep-2-0 = ["gnustep-1-9", "objc2/gnustep-2-0", "objc2-foundation/gnustep-2-0"]
+gnustep-2-1 = ["gnustep-2-0", "objc2/gnustep-2-1", "objc2-foundation/gnustep-2-1"]
 
-all = ["objc2-foundation?/block2", "objc2-foundation?/NSObject", "objc2-foundation?/NSZone"]
+all = ["objc2-foundation/block2", "objc2-foundation/NSObject", "objc2-foundation/NSZone"]
 
 # Hack to prevent the feature flag from being enabled in the entire project
-assembly-features = ["all", "objc2?/unstable-static-sel-inlined", "objc2?/unstable-static-class-inlined"]
+assembly-features = ["all", "objc2/unstable-static-sel-inlined", "objc2/unstable-static-class-inlined"]
 
 [package.metadata.release]
 release = false

crates/test-ui/Cargo.toml

@@ -39,13 +39,13 @@ gnustep-2-1 = ["gnustep-2-0", "block2/gnustep-2-1", "objc2/gnustep-2-1", "objc2-
 trybuild = { version = "1.0.72", optional = true }
 block2 = { path = "../block2" }
 objc2 = { path = "../objc2" }
-objc2-foundation = { path = "../../framework-crates/objc2-foundation" }
+objc2-foundation = { path = "../../framework-crates/objc2-foundation", default-features = false, features = ["std"] }
 
 # To make CI work
 [target.'cfg(not(target_vendor = "apple"))'.dependencies]
 block2 = { path = "../block2", features = ["gnustep-1-7"] }
 objc2 = { path = "../objc2", features = ["gnustep-1-7"] }
-objc2-foundation = { path = "../../framework-crates/objc2-foundation", features = ["gnustep-1-7"] }
+objc2-foundation = { path = "../../framework-crates/objc2-foundation", default-features = false, features = ["std", "gnustep-1-7"] }
 
 [[bin]]
 name = "test-ui"

crates/tests/Cargo.toml

@@ -38,7 +38,7 @@ unstable-objfw = ["block2/unstable-objfw", "objc2/unstable-objfw"]
 [dependencies]
 block2 = { path = "../block2" }
 objc2 = { path = "../objc2" }
-objc2-foundation = { path = "../../framework-crates/objc2-foundation" }
+objc2-foundation = { path = "../../framework-crates/objc2-foundation", default-features = false, features = ["std"] }
 
 [build-dependencies]
 cc = "1.0"