Warning message if guards without allocator enabled

Cargo.toml

@@ -19,7 +19,11 @@ maintenance = { status = "actively-developed" }
 
 [dependencies]
 libc = "0.2"
+log = "0.4"
 spin = "0.4"
 thread-id = "3.3"
 
 qadapt-macro = { version = "0.7.0", path = "./qadapt-macro" }
+
+[dev-dependencies]
+env_logger = "0.6"

examples/release_mode.rs

@@ -14,6 +14,7 @@ fn does_allocate() -> Box<u8> {
 fn main() {
     // If you were to run `cargo run --example release_mode`, this program blows up.
     // If, however, you ran `cargo run --release --example release_mode`,
-    // nothing interesting will happen.
+    // nothing interesting will happen since panic-related code is stripped
+    // for release builds.
     does_allocate();
 }

examples/setup_warning.rs

@@ -0,0 +1,21 @@
+extern crate env_logger;
+extern crate qadapt;
+
+use qadapt::allocate_panic;
+
+// Note that we're missing the `#[global_allocator]` attribute
+
+#[allocate_panic]
+fn does_allocate() -> Box<u8> {
+    Box::new(0)
+}
+
+fn main() {
+    // This code will warn that QADAPT isn't being used, but won't trigger a panic.
+    // Run with `RUST_LOG=warn cargo run --example setup_warning`
+    env_logger::init();
+    does_allocate();
+
+    // The warning will only trigger once though
+    does_allocate();
+}

src/lib.rs

@@ -12,6 +12,8 @@
 //! for some helper macros to make working with QADAPT a bit easier.
 #![deny(missing_docs)]
 extern crate libc;
+#[macro_use]
+extern crate log;
 extern crate qadapt_macro;
 extern crate spin;
 // thread_id is necessary because `std::thread::current()` panics if we have not yet
@@ -45,6 +47,11 @@ pub fn enter_protected() {
             return;
         }
 
+        if *IS_ACTIVE.read() == false {
+            *IS_ACTIVE.write() = true;
+            warn!("QADAPT not initialized when using allocation guards; please verify `#[global_allocator]` is set!");
+        }
+
         PROTECTION_LEVEL
             .try_with(|v| {
                 *v.write() += 1;
@@ -76,6 +83,7 @@ pub fn exit_protected() {
     }
 }
 
+static IS_ACTIVE: RwLock<bool> = RwLock::new(false);
 static INTERNAL_ALLOCATION: RwLock<usize> = RwLock::new(usize::max_value());
 
 /// Get the current "protection level" in QADAPT: calls to enter_protected() - exit_protected()
@@ -115,6 +123,10 @@ fn alloc_immediate() -> bool {
 
 unsafe impl GlobalAlloc for QADAPT {
     unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        if *IS_ACTIVE.read() == false {
+            *IS_ACTIVE.write() = true;
+        }
+
         // If we're attempting to allocate our PROTECTION_LEVEL thread local,
         // just allow it through
         if alloc_immediate() {