Allow bitflags v1 and v2 to coexist

CHANGELOG.md

@@ -49,6 +49,8 @@ We have several packages which live in this repository. Changes are tracked sepa
 
 ### [defmt-next]
 
+* [#894] Add optional support for bitflags v2
+
 * [#938] Emit `option_env!("DEFMT_LOG")` so rustc depinfo can track it
 * [#935] Add note in book's setup chapter to clarify staticlib setup
 * [#914] Add cargo-deny as a CI action to check crate security and licensing
@@ -845,6 +847,7 @@ Initial release
 [#901]: https://github.com/knurling-rs/defmt/pull/901
 [#899]: https://github.com/knurling-rs/defmt/pull/899
 [#897]: https://github.com/knurling-rs/defmt/pull/897
+[#894]: https://github.com/knurling-rs/defmt/pull/894
 [#889]: https://github.com/knurling-rs/defmt/pull/889
 [#887]: https://github.com/knurling-rs/defmt/pull/887
 [#884]: https://github.com/knurling-rs/defmt/pull/884

defmt/Cargo.toml

@@ -21,6 +21,7 @@ version = "0.3.10"
 alloc = []
 avoid-default-panic = []
 ip_in_core = []
+bitflagsv2 = ["dep:bitflagsv2"]
 
 # Encoding feature flags. These should only be set by end-user crates, not by library crates.
 #
@@ -47,6 +48,7 @@ unstable-test = [ "defmt-macros/unstable-test" ]
 # defmt. Although, multiple versions of defmt might use the *same* defmt-macros.
 defmt-macros = { path = "../macros", version = "=0.4.0" }
 bitflags = "1"
+bitflagsv2 = { package = "bitflags", version = "2", optional = true }
 
 [dev-dependencies]
 rustc_version = "0.4"

defmt/src/export/mod.rs

@@ -8,6 +8,9 @@ use crate::{Format, Formatter, Str};
 pub use self::integers::*;
 pub use bitflags::bitflags;
 
+#[cfg(feature = "bitflagsv2")]
+pub use bitflagsv2::bitflags as bitflagsv2;
+
 pub trait UnsignedInt {}
 impl UnsignedInt for u8 {}
 impl UnsignedInt for u16 {}

defmt/src/lib.rs

@@ -337,7 +337,7 @@ pub use defmt_macros::timestamp;
 
 /// Generates a bitflags structure that can be formatted with defmt.
 ///
-/// This macro is a wrapper around the [`bitflags!`] crate, and provides an (almost) identical
+/// This macro is a wrapper around the [`bitflags!`] macro of the bitflags version 1 crate, and provides an (almost) identical
 /// interface. Refer to [its documentation] for an explanation of the syntax.
 ///
 /// [its documentation]: https://docs.rs/bitflags/1/bitflags/
@@ -367,6 +367,44 @@ pub use defmt_macros::timestamp;
 /// ```
 pub use defmt_macros::bitflags;
 
+/// Generates a bitflags structure that can be formatted with defmt (using version 2 of the bitflags crate)
+///
+
+/// Users of the defmt crate can enable the bitflagsv2 feature by adding `defmt = {version = "1", features = ["bitflagsv2"] }`
+/// to their Cargo.toml. Bitflags version 2 introduces significant improvements over version 1, including a safer
+/// API with the replacement of the unsafe from_bits_unchecked method by the safe from_bits_retain method
+/// and enhanced serialization support via an optional serde feature.
+/// This macro is a wrapper around the [`bitflags!`][bitflagsv2] macro of the bitflags version 2 crate, and provides an (almost) identical
+/// interface. Refer to [its documentation][bitflagsv2] for an explanation of the syntax.
+///
+/// [bitflagsv2]: https://docs.rs/bitflags/2/bitflags/macro.bitflags.html
+///
+/// # Limitations
+///
+/// This macro only supports bitflags structs represented as one of Rust's built-in unsigned integer
+/// types (`u8`, `u16`, `u32`, `u64`, or `u128`). Custom types are not supported. This restriction
+/// is necessary to support defmt's efficient encoding.
+///
+/// # Examples
+///
+/// The example from the bitflagsv2 crate works as-is:
+///
+/// ```
+/// #[cfg(feature = "bitflagsv2")]
+/// defmt::bitflagsv2! {
+///     struct Flags: u32 {
+///         const A = 0b00000001;
+///         const B = 0b00000010;
+///         const C = 0b00000100;
+///         const ABC = Self::A.bits() | Self::B.bits() | Self::C.bits()
+///     }
+/// }
+/// defmt::info!("Flags::ABC: {}", Flags::ABC);
+/// defmt::info!("Flags::empty(): {}", Flags::empty());
+/// ```
+#[cfg(feature = "bitflagsv2")]
+pub use defmt_macros::bitflagsv2;
+
 #[doc(hidden)] // documented as the `Format` trait instead
 pub use defmt_macros::Format;
 

firmware/qemu/Cargo.toml

@@ -11,7 +11,7 @@ name = "defmt-test"
 harness = false
 
 [dependencies]
-defmt = { path = "../../defmt" }
+defmt = { path = "../../defmt", default-features = true, features = ["bitflagsv2"]}
 defmt-semihosting = { path = "../defmt-semihosting" }
 defmt-test = { path = "../defmt-test" }
 cortex-m = "0.7"

firmware/qemu/src/bin/bitflagsv2.out

@@ -0,0 +1,12 @@
+INFO Flags::empty(): FLAG_0
+INFO Flags::empty(): Flags(0x0) (fmt::Debug)
+INFO Flags::all(): FLAG_1 | FLAG_2 | FLAG_7 | FLAG_7_COPY
+INFO Flags::all(): Flags(FLAG_1 | FLAG_2 | FLAG_7) (fmt::Debug)
+INFO Flags::FLAG_1: FLAG_1
+INFO Flags::FLAG_1: Flags(FLAG_1) (fmt::Debug)
+INFO Flags::FLAG_7: FLAG_7 | FLAG_7_COPY
+INFO Flags::FLAG_7: Flags(FLAG_7) (fmt::Debug)
+INFO LargeFlags::ALL: MSB | ALL | NON_LITERAL
+INFO LargeFlags::ALL: LargeFlags(MSB | ALL) (fmt::Debug)
+INFO LargeFlags::empty(): (empty)
+INFO LargeFlags::empty(): LargeFlags(0x0) (fmt::Debug)

firmware/qemu/src/bin/bitflagsv2.rs

@@ -0,0 +1,81 @@
+#![no_std]
+#![no_main]
+#![allow(clippy::bad_bit_mask)]
+
+use cortex_m_rt::entry;
+use cortex_m_semihosting::debug;
+use defmt::{bitflagsv2, Debug2Format};
+
+use defmt_semihosting as _; // global logger
+
+bitflagsv2! {
+    #[derive(Debug)]
+    struct Flags: u8 {
+        #[cfg(not(never))]
+        const FLAG_0 = 0b00;
+        const FLAG_1 = 0b01;
+        const FLAG_2 = 0b10;
+        const FLAG_7 = 1 << 7;
+        const FLAG_7_COPY = Self::FLAG_7.bits();
+        #[cfg(never)]
+        const CFGD_OUT = 1;
+    }
+}
+
+bitflagsv2! {
+    #[derive(Debug)]
+    struct LargeFlags: u128 {
+        const MSB = 1 << 127;
+        const ALL = !0;
+        const NON_LITERAL = compute_flag_value(0x346934553632462);
+    }
+}
+
+const fn compute_flag_value(x: u128) -> u128 {
+    x ^ 0xdeadbeef
+}
+
+#[entry]
+fn main() -> ! {
+    defmt::info!("Flags::empty(): {}", Flags::empty());
+    defmt::info!(
+        "Flags::empty(): {} (fmt::Debug)",
+        Debug2Format(&Flags::empty())
+    );
+    defmt::info!("Flags::all(): {}", Flags::all());
+    defmt::info!("Flags::all(): {} (fmt::Debug)", Debug2Format(&Flags::all()));
+    defmt::info!("Flags::FLAG_1: {}", Flags::FLAG_1);
+    defmt::info!(
+        "Flags::FLAG_1: {} (fmt::Debug)",
+        Debug2Format(&Flags::FLAG_1)
+    );
+    defmt::info!("Flags::FLAG_7: {}", Flags::FLAG_7);
+    defmt::info!(
+        "Flags::FLAG_7: {} (fmt::Debug)",
+        Debug2Format(&Flags::FLAG_7)
+    );
+
+    defmt::info!("LargeFlags::ALL: {}", LargeFlags::ALL);
+    defmt::info!(
+        "LargeFlags::ALL: {} (fmt::Debug)",
+        Debug2Format(&LargeFlags::ALL)
+    );
+    defmt::info!("LargeFlags::empty(): {}", LargeFlags::empty());
+    defmt::info!(
+        "LargeFlags::empty(): {} (fmt::Debug)",
+        Debug2Format(&LargeFlags::empty())
+    );
+
+    loop {
+        debug::exit(debug::EXIT_SUCCESS)
+    }
+}
+
+// like `panic-semihosting` but doesn't print to stdout (that would corrupt the defmt stream)
+#[cfg(target_os = "none")]
+#[panic_handler]
+fn panic(_: &core::panic::PanicInfo) -> ! {
+    loop {
+        debug::exit(debug::EXIT_FAILURE)
+    }
+}

macros/src/items/bitflags.rs

@@ -1,6 +1,6 @@
 use proc_macro::TokenStream;
 use proc_macro2::TokenStream as TokenStream2;
-use quote::{quote, ToTokens};
+use quote::{format_ident, quote, ToTokens};
 use syn::parse_macro_input;
 
 use crate::{cargo, construct};
@@ -9,7 +9,7 @@ use self::input::Input;
 
 mod input;
 
-pub(crate) fn expand(input: TokenStream) -> TokenStream {
+pub(crate) fn expand(input: TokenStream, is_v2: bool) -> TokenStream {
     let bitflags_input = TokenStream2::from(input.clone());
     let input = parse_macro_input!(input as Input);
 
@@ -23,11 +23,13 @@ pub(crate) fn expand(input: TokenStream) -> TokenStream {
         construct::crate_local_disambiguator(),
         cargo::crate_name(),
     );
-    let format_tag = construct::interned_string(&format_string, "bitflags", false, None);
+    let bitflags_tag = if is_v2 { "bitflagsv2" } else { "bitflags" };
+    let format_tag = construct::interned_string(&format_string, bitflags_tag, false, None);
 
     let ident = input.ident();
     let ty = input.ty();
-    let flag_statics = codegen_flag_statics(&input);
+    let flag_statics = codegen_flag_statics(&input, is_v2);
+    let bitflag_macro = format_ident!("{bitflags_tag}");
     quote!(
         const _: () = {
             fn assert<T: defmt::export::UnsignedInt>() {}
@@ -36,7 +38,7 @@ pub(crate) fn expand(input: TokenStream) -> TokenStream {
             #(#flag_statics)*
         };
 
-        defmt::export::bitflags! {
+        defmt::export::#bitflag_macro! {
             #bitflags_input
         }
 
@@ -59,7 +61,7 @@ pub(crate) fn expand(input: TokenStream) -> TokenStream {
     .into()
 }
 
-fn codegen_flag_statics(input: &Input) -> Vec<TokenStream2> {
+fn codegen_flag_statics(input: &Input, is_v2: bool) -> Vec<TokenStream2> {
     input
         .flags()
         .enumerate()
@@ -69,11 +71,21 @@ fn codegen_flag_statics(input: &Input) -> Vec<TokenStream2> {
             let struct_name = input.ident();
             let repr_ty = input.ty();
 
+            let _tag = if is_v2 {
+                "bitflagsv2_value"
+            } else {
+                "bitflags_value"
+            };
             let sym_name = construct::mangled_symbol_name(
-                "bitflags_value",
+                _tag,
                 &format!("{}::{i}::{}", input.ident(), flag.ident()),
             );
 
+            let bits_access = if is_v2 {
+                quote! { bits() }
+            } else {
+                quote! { bits }
+            };
             quote! {
                 #(#cfg_attrs)*
                 #[cfg_attr(target_os = "macos", link_section = ".defmt,end")]
@@ -84,7 +96,7 @@ fn codegen_flag_statics(input: &Input) -> Vec<TokenStream2> {
                     // causes a value such as `1 << 127` to be evaluated as an `i32`, which
                     // overflows. So we instead coerce (but don't cast) it to the bitflags' raw
                     // type, and then cast that to u128.
-                    let coerced_value: #repr_ty = #struct_name::#var_name.bits;
+                    let coerced_value: #repr_ty = #struct_name::#var_name.#bits_access;
                     coerced_value as u128
                 };
             }

macros/src/lib.rs

@@ -199,7 +199,14 @@ pub fn write(args: TokenStream) -> TokenStream {
 #[proc_macro]
 #[proc_macro_error]
 pub fn bitflags(ts: TokenStream) -> TokenStream {
-    items::bitflags::expand(ts)
+    items::bitflags::expand(ts, false)
+}
+
+/* # Items */
+#[proc_macro]
+#[proc_macro_error]
+pub fn bitflagsv2(ts: TokenStream) -> TokenStream {
+    items::bitflags::expand(ts, true)
 }
 
 #[proc_macro]