Make unwinding an optional feature

Author: Amanieu

Cargo.toml

@@ -19,9 +19,10 @@ version = "1.0.0"
 simd = "0.1"
 
 [features]
-default = ["alloc", "valgrind"]
+default = ["alloc", "valgrind", "unwind"]
 alloc = []
 valgrind = ["valgrind_request"]
+unwind = []
 
 # These apply only to tests within this library; assembly at -O0 is completely
 # unreadable, so use -O1.

src/generator.rs

@@ -218,7 +218,9 @@ impl<'a, Input, Output, Stack> Generator<'a, Input, Output, Stack>
   /// Extracts the stack from a generator without checking if the generator function has returned.
   /// This will leave any pointers into the generator stack dangling, and won't run destructors.
   pub unsafe fn unsafe_unwrap(mut self) -> Stack {
-    self.stack_ptr.map(|stack_ptr| arch::unwind(stack_ptr, self.stack.inner.base()));
+    if cfg!(feature = "unwind") {
+      self.stack_ptr.map(|stack_ptr| arch::unwind(stack_ptr, self.stack.inner.base()));
+    }
 
     // We can't just return self.stack since Generator has a Drop impl
     let stack = ptr::read(&self.stack.inner);
@@ -232,8 +234,11 @@ impl<'a, Input, Output, Stack> Drop for Generator<'a, Input, Output, Stack>
     where Input: 'a, Output: 'a, Stack: stack::Stack {
   fn drop(&mut self) {
     unsafe {
-      self.stack_ptr.map(|stack_ptr| arch::unwind(stack_ptr, self.stack.inner.base()));
-      ptr::drop_in_place(&mut self.stack.inner);
+      // If unwinding is not available then we have to leak the stack.
+      if cfg!(feature = "unwind") {
+        self.stack_ptr.map(|stack_ptr| arch::unwind(stack_ptr, self.stack.inner.base()));
+        ptr::drop_in_place(&mut self.stack.inner);
+      }
     }
   }
 }

src/lib.rs

@@ -43,6 +43,11 @@ pub const STACK_ALIGNMENT: usize = arch::STACK_ALIGNMENT;
 
 mod debug;
 
+#[cfg(feature = "unwind")]
+#[path = "unwind.rs"]
+mod unwind;
+#[cfg(not(feature = "unwind"))]
+#[path = "no_unwind.rs"]
 mod unwind;
 
 pub mod generator;

src/no_unwind.rs

@@ -0,0 +1,23 @@
+// This file is part of libfringe, a low-level green threading library.
+// Copyright (c) Amanieu d'Antras <[email protected]>,
+// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
+// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
+// http://opensource.org/licenses/MIT>, at your option. This file may not be
+// copied, modified, or distributed except according to those terms.
+
+use arch::StackPointer;
+
+pub unsafe extern "C" fn unwind_wrapper(arg: usize, sp: StackPointer, _stack_base: *mut u8,
+                                        f: unsafe fn(usize, StackPointer)) -> usize {
+  f(arg, sp);
+  0
+}
+
+pub unsafe extern "C" fn start_unwind(_panic: usize) -> ! {
+  unreachable!();
+}
+
+#[inline]
+pub fn unwind_arg(_stack_base: *mut u8) -> usize {
+  unreachable!();
+}