remove sentinel, put statics in .rdata

Author: Robo210

src/lib.rs

@@ -215,7 +215,6 @@ macro_rules! etw_event {
         };
 
         // These two statics need to be mut to avoid compiler errors about *const EventMetadata not being Sync.
-        // It's unclear why mut avoids these errors.
 
         paste! {
             #[cfg(target_os = "linux")]
@@ -227,7 +226,7 @@ macro_rules! etw_event {
 
         paste! {
             #[cfg(target_os = "windows")]
-            #[link_section = ".rsdata$zRSETW5"]
+            #[link_section = ".rdata$zRSETW5"]
             #[allow(non_upper_case_globals)]
             #[used]
             static mut [<ETW_META_PTR $name>]: *const $crate::_details::EventMetadata = &ETW_META;

src/native/etw.rs

@@ -6,13 +6,13 @@ use tracelogging::*;
 use tracelogging_dynamic::EventBuilder;
 use tracing_subscriber::registry::{LookupSpan, SpanRef};
 
-// Items within this .rsdata section will be sorted alphabetically, thus the start is named with "0", the end "9", and each metadata "5".
+// Items within this .rdata section will be sorted alphabetically, thus the start is named with "0", the end "9", and each metadata "5".
 // If these statics aren't mut then everything will silently fail to work.
 #[allow(non_upper_case_globals)]
-#[link_section = ".rsdata$zRSETW0"]
+#[link_section = ".rdata$zRSETW0"]
 pub(crate) static mut _start__etw_kw: usize = 0;
 #[allow(non_upper_case_globals)]
-#[link_section = ".rsdata$zRSETW9"]
+#[link_section = ".rdata$zRSETW9"]
 pub(crate) static mut _stop__etw_kw: usize = 0;
 
 thread_local! {static EBW: std::cell::RefCell<EventBuilder>  = RefCell::new(EventBuilder::new());}

src/native/mod.rs

@@ -15,12 +15,6 @@ pub mod noop;
 #[cfg(not(any(target_os = "windows", target_os = "linux")))]
 #[doc(hidden)]
 pub use noop::Provider;
-#[cfg(not(any(target_os = "windows", target_os = "linux")))]
-#[doc(hidden)]
-pub(crate) use noop::_start__etw_kw;
-#[cfg(not(any(target_os = "windows", target_os = "linux")))]
-#[doc(hidden)]
-pub(crate) use noop::_stop__etw_kw;
 
 #[cfg(target_os = "linux")]
 #[doc(hidden)]
@@ -41,9 +35,6 @@ pub(crate) use tracelogging_dynamic::Guid as native_guid;
 #[cfg(target_os = "linux")]
 pub(crate) use eventheader::Guid as native_guid;
 
-// Used to detect the noop implementation, for testing purposes
-pub(crate) const MAGIC_STATICS_SENTINEL: usize = usize::from_ne_bytes(*b"NO-OPT00");
-
 use crate::error::EtwError;
 
 #[doc(hidden)]

src/native/noop.rs

@@ -4,12 +4,6 @@ use tracing_subscriber::registry::{LookupSpan, SpanRef};
 
 use crate::error::EtwError;
 
-// We use this magic value to determine
-#[allow(non_upper_case_globals)]
-pub(crate) static _start__etw_kw: usize = super::MAGIC_STATICS_SENTINEL;
-#[allow(non_upper_case_globals)]
-pub(crate) static _stop__etw_kw: usize = super::MAGIC_STATICS_SENTINEL;
-
 #[doc(hidden)]
 pub struct Provider;
 

src/statics.rs

@@ -19,18 +19,9 @@ pub(crate) static GLOBAL_ACTIVITY_SEED: LazyLock<[u8; 16]> = LazyLock::new(|| {
         data
     });
 
-static EVENT_METADATA: LazyLock<Box<[ParsedEventMetadata]>> = LazyLock::new(|| {
+fn process_static_metadata() -> Box<[ParsedEventMetadata]> {
     // The array of pointers are in a mutable section and can be sorted/deduped, but they are pointing to read-only static data
 
-    // unsafe is necessary on Linux but not Windows
-    #[allow(unused_unsafe)]
-    // SAFETY These aren't "real" extern statics, they are magic statics generated by gcc/llvm that cannot be mutated by other threads.
-    unsafe {
-        if crate::native::_start__etw_kw == crate::native::MAGIC_STATICS_SENTINEL {
-            return Box::new([]);
-        }
-    }
-
     let start =
         &raw const crate::native::_start__etw_kw as *mut *const EventMetadata;
     let stop =
@@ -105,7 +96,13 @@ static EVENT_METADATA: LazyLock<Box<[ParsedEventMetadata]>> = LazyLock::new(|| {
     let mut sorted = vec.into_boxed_slice();
     sorted.sort_unstable_by(|a, b| b.cmp(a));
     sorted
-});
+}
+
+#[cfg(any(target_os = "windows", target_os = "linux"))]
+static EVENT_METADATA: LazyLock<Box<[ParsedEventMetadata]>> = LazyLock::new(process_static_metadata);
+
+#[cfg(not(any(target_os = "windows", target_os = "linux")))]
+static EVENT_METADATA: [ParsedEventMetadata; 0] = [];
 
 impl core::cmp::PartialEq for ParsedEventMetadata {
     fn eq(&self, other: &Self) -> bool {
@@ -223,15 +220,10 @@ mod test {
             sum += event.kw;
         }
 
-        #[allow(unused_unsafe)]
-        let expected = unsafe {
-            if crate::native::_start__etw_kw != crate::native::MAGIC_STATICS_SENTINEL {
-                55
-            }
-            else {
-                0
-            }
-        };
+        #[cfg(any(target_os = "windows", target_os = "linux"))]
+        let expected = 55;
+        #[cfg(not(any(target_os = "windows", target_os = "linux")))]
+        let expected = 0;
 
         assert_eq!(sum, expected);
     }