make std feature conflict with hashbrown in compile error and gate free_list_allocator by feature

Author: CrazyboyQCD

src/allocator/dedicated_block_allocator/mod.rs

@@ -101,17 +101,20 @@ impl SubAllocator for DedicatedBlockAllocator {
     ) {
         let empty = "".to_string();
         let name = self.name.as_ref().unwrap_or(&empty);
-
-        let backtrace_info = if cfg!(feature = "std") {
-            format!(
+        let backtrace_info;
+        #[cfg(feature = "std")]
+        {
+            backtrace_info = format!(
                 r#"
-        backtrace: {}
-    "#,
+            backtrace: {}
+        "#,
                 self.backtrace
             )
-        } else {
-            "".to_owned()
-        };
+        }
+        #[cfg(not(feature = "std"))]
+        {
+            backtrace_info = "".to_owned()
+        }
 
         log!(
             log_level,

src/allocator/free_list_allocator/mod.rs

@@ -5,12 +5,15 @@ use alloc::{
     string::{String, ToString},
     vec::Vec,
 };
-#[cfg(all(feature = "std", not(feature = "hashbrown")))]
-use std::collections::{HashMap, HashSet};
+
 #[cfg(feature = "std")]
-use std::{backtrace::Backtrace, sync::Arc};
+use std::{
+    backtrace::Backtrace,
+    collections::{HashMap, HashSet},
+    sync::Arc,
+};
 
-#[cfg(all(not(feature = "std"), feature = "hashbrown"))]
+#[cfg(feature = "hashbrown")]
 use hashbrown::{HashMap, HashSet};
 use log::{log, Level};
 
@@ -377,16 +380,20 @@ impl SubAllocator for FreeListAllocator {
             }
             let empty = "".to_string();
             let name = chunk.name.as_ref().unwrap_or(&empty);
-            let backtrace_info = if cfg!(feature = "std") {
-                format!(
+            let backtrace_info;
+            #[cfg(feature = "std")]
+            {
+                backtrace_info = format!(
                     r#"
             backtrace: {}
         "#,
                     chunk.backtrace
                 )
-            } else {
-                "".to_owned()
-            };
+            }
+            #[cfg(not(feature = "std"))]
+            {
+                backtrace_info = "".to_owned()
+            }
             log!(
                 log_level,
                 r#"leak detected: {{

src/allocator/mod.rs

@@ -10,7 +10,9 @@ use crate::result::*;
 pub(crate) mod dedicated_block_allocator;
 pub(crate) use dedicated_block_allocator::DedicatedBlockAllocator;
 
+#[cfg(any(feature = "std", feature = "hashbrown"))]
 pub(crate) mod free_list_allocator;
+#[cfg(any(feature = "std", feature = "hashbrown"))]
 pub(crate) use free_list_allocator::FreeListAllocator;
 
 #[derive(PartialEq, Copy, Clone, Debug)]

src/lib.rs

@@ -222,8 +222,8 @@
 #[macro_use]
 extern crate alloc;
 
-#[cfg(all(not(feature = "std"), not(feature = "hashbrown")))]
-compile_error!("\"hashbrown\" feature should be enabled in \"no_std\" environment.");
+#[cfg(all(feature = "std", feature = "hashbrown"))]
+compile_error!("\"hashbrown\" feature should not be enabled in \"std\" environment.");
 
 #[cfg(all(not(feature = "std"), feature = "visualizer"))]
 compile_error!("Cannot enable \"visualizer\" feature in \"no_std\" environment.");