Add compile_error! for mutually exclusive features

defmt feature is incompatible with log and std.

In mctp-estack, move the compile_error prior to 'mod' items.
Otherwise it prints warnings in every module.

Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>

Author: mkj

mctp-estack/src/lib.rs

@@ -45,6 +45,11 @@ use heapless::FnvIndexMap;
 
 use mctp::{Eid, Error, MsgIC, MsgType, Result, Tag, TagValue};
 
+#[cfg(not(any(feature = "log", feature = "defmt")))]
+compile_error!("Either log or defmt feature must be enabled");
+#[cfg(all(feature = "log", feature = "defmt"))]
+compile_error!("log and defmt features are mutually exclusive");
+
 pub mod control;
 pub mod fragment;
 pub mod i2c;
@@ -733,9 +738,6 @@ impl EventStamp {
     }
 }
 
-#[cfg(not(any(feature = "log", feature = "defmt")))]
-compile_error!("Either log or defmt feature must be enabled");
-
 pub(crate) mod fmt {
     #[cfg(feature = "defmt")]
     pub use defmt::{debug, error, info, trace, warn};

mctp-usb-embassy/src/mctpusb.rs

@@ -12,6 +12,8 @@ use log::{debug, error, info, trace, warn};
 
 #[cfg(not(any(feature = "log", feature = "defmt")))]
 compile_error!("Either log or defmt feature must be enabled");
+#[cfg(all(feature = "log", feature = "defmt"))]
+compile_error!("log and defmt features are mutually exclusive");
 
 use core::ops::Range;
 

mctp/src/lib.rs

@@ -18,6 +18,11 @@
 
 use core::future::Future;
 
+// Currently there is no defmt::Format implementation for std::io::Error
+// (can't be derived). If needed that could be manually implemented.
+#[cfg(all(feature = "std", feature = "defmt"))]
+compile_error!("std and defmt features are currently mutually exclusive");
+
 /// MCTP endpoint ID
 #[derive(Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd, Hash)]
 #[cfg_attr(feature = "defmt", derive(defmt::Format))]