Remove no_run from doctests

Uses `qadapt::is_active` to work around rust-lang/cargo#6570.
Currently assumes that *some* allocation will have happened
by the time `fn main()` is called, which is sub-par.

src/lib.rs

@@ -17,23 +17,27 @@
 //! Actually making use of QADAPT is straight-forward. To set up the allocator,
 //! place the following snippet in either your program binaries (main.rs) or tests:
 //!
-//! ```rust,no_run
+//! ```rust
 //! use qadapt::QADAPT;
 //!
 //! #[global_allocator]
 //! static Q: QADAPT = QADAPT;
 //!
 //! fn main() {
+//!     # // Because `debug_assertions` are on for doctests in release mode
+//!     # // we have to add an extra guard.
+//!     # if qadapt::is_active() {
 //!     if cfg!(debug_assertions) {
 //!         assert!(qadapt::is_active());
 //!     }
+//!     # }
 //! }
 //! ```
 //!
 //! After that, there are two ways of telling QADAPT that it should trigger a panic:
 //!
 //! 1. Annotate functions with the `#[no_alloc]` proc macro:
-//! ```rust,no_run
+//! ```rust
 //! use qadapt::no_alloc;
 //! use qadapt::QADAPT;
 //! use std::panic::catch_unwind;
@@ -57,7 +61,9 @@
 //!     do_math();
 //!
 //!     let err = catch_unwind(|| does_panic());
+//!     # if qadapt::is_active() {
 //!     assert!(err.is_err());
+//!     # }
 //! }
 //! ```
 //!
@@ -96,22 +102,27 @@ use std::thread;
 thread_local! {
     static PROTECTION_LEVEL: RwLock<usize> = RwLock::new(0);
 }
+static IS_ACTIVE: RwLock<bool> = RwLock::new(false);
+static INTERNAL_ALLOCATION: RwLock<usize> = RwLock::new(usize::max_value());
+
 
 /// The QADAPT allocator itself
 ///
 /// To make use of the allocator, include this code block in your program
 /// binaries/tests:
 ///
-/// ```rust,no_run
+/// ```rust
 /// use qadapt::QADAPT;
 ///
 /// #[global_allocator]
 /// static Q: QADAPT = QADAPT;
 ///
 /// fn main() {
+///     # if qadapt::is_active() {
 ///     if cfg!(debug_assertions) {
 ///         assert!(qadapt::is_active());
 ///     }
+///     # }
 /// }
 /// ```
 pub struct QADAPT;
@@ -228,7 +239,7 @@ pub fn exit_protected() {
 /// in code that was not intended to be allocation-free. The compiler will warn you
 /// that there is an unreachable statement if this happens.
 ///
-/// ```rust,no_run
+/// ```rust
 /// use qadapt::assert_no_alloc;
 /// use qadapt::QADAPT;
 /// use std::panic::catch_unwind;
@@ -247,8 +258,10 @@ pub fn exit_protected() {
 ///     // QADAPT allocation guards, this triggers a panic:
 ///     // `Box::new` forces an allocation, and QADAPT still thinks
 ///     // we're in a protected region because of the return in  `early_return()`
+///     # if qadapt::is_active() {
 ///     let res = catch_unwind(|| Box::new(x));
 ///     assert!(res.is_err());
+///     # }
 /// }
 #[macro_export]
 macro_rules! assert_no_alloc {
@@ -260,16 +273,13 @@ macro_rules! assert_no_alloc {
     }};
 }
 
-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()`.
 ///
 /// **Note**: For release builds, `protection_level()` will always return 0.
 ///
 /// **Example**:
 ///
-/// ```rust,no_run
+/// ```rust
 /// use qadapt::enter_protected;
 /// use qadapt::exit_protected;
 /// use qadapt::QADAPT;
@@ -279,6 +289,7 @@ static INTERNAL_ALLOCATION: RwLock<usize> = RwLock::new(usize::max_value());
 /// static Q: QADAPT = QADAPT;
 ///
 /// fn main() {
+///     # if qadapt::is_active() {
 ///     enter_protected();
 ///     // We're now in an allocation-protected code region
 ///     assert_eq!(1, protection_level());
@@ -288,6 +299,7 @@ static INTERNAL_ALLOCATION: RwLock<usize> = RwLock::new(usize::max_value());
 ///     assert_eq!(2, protection_level());
 ///     exit_protected();
 ///     exit_protected();
+///     # }
 ///     
 ///     // It's now safe to allocate/drop
 /// }
@@ -302,7 +314,7 @@ pub fn protection_level() -> usize {
 ///
 /// **Example**:
 ///
-/// ```rust,no_run
+/// ```rust
 /// use qadapt::is_active;
 /// use qadapt::QADAPT;
 ///
@@ -310,9 +322,11 @@ pub fn protection_level() -> usize {
 /// static Q: QADAPT = QADAPT;
 ///
 /// pub fn main() {
+///     # if qadapt::is_active() {
 ///     if cfg!(debug_assertions) {
 ///         assert!(is_active());
 ///     }
+///     # }
 /// }
 /// ```
 pub fn is_active() -> bool {