rand: bubble up IO messages futher.

The various ...Rng::new() methods can hit IO errors from the OSRng they use,
and it seems sensible to expose them at a higher level. Unfortunately, writing
e.g. `StdRng::new().unwrap()` gives a much poorer error message than if it
failed internally, but this is a problem with all `IoResult`s.

14 files changed, 102 insertions, 77 deletions

diff --git a/src/libcollections/deque.rs b/src/libcollections/deque.rs
index 05df04d293f..6fd525bac2e 100644
--- a/src/libcollections/deque.rs
+++ b/src/libcollections/deque.rs
@@ -52,7 +52,7 @@ pub mod bench {
                                                   map: &mut M,
                                                   bh: &mut BenchHarness) {
         // setup
-        let mut rng = rand::XorShiftRng::new();
+        let mut rng = rand::weak_rng();
 
         map.clear();
         for _ in range(0, n) {
@@ -89,7 +89,7 @@ pub mod bench {
                                                 map: &mut M,
                                                 bh: &mut BenchHarness) {
         // setup
-        let mut rng = rand::XorShiftRng::new();
+        let mut rng = rand::weak_rng();
         let mut keys = slice::from_fn(n, |_| rng.gen::<uint>() % n);
 
         for k in keys.iter() {
diff --git a/src/libgreen/sched.rs b/src/libgreen/sched.rs
index 5571d4f4687..c38d136e939 100644
--- a/src/libgreen/sched.rs
+++ b/src/libgreen/sched.rs
@@ -966,7 +966,12 @@ impl ClosureConverter for UnsafeTaskReceiver {
 // worry there.
 #[cfg(windows)]
 fn new_sched_rng() -> XorShiftRng {
-    XorShiftRng::new()
+    match XorShiftRng::new() {
+        Ok(r) => r,
+        Err(e) => {
+            rtabort!("sched: failed to create seeded RNG: {}", e)
+        }
+    }
 }
 #[cfg(unix)]
 fn new_sched_rng() -> XorShiftRng {
diff --git a/src/librand/distributions/exponential.rs b/src/librand/distributions/exponential.rs
index 369828d5969..889c83b28c2 100644
--- a/src/librand/distributions/exponential.rs
+++ b/src/librand/distributions/exponential.rs
@@ -126,7 +126,7 @@ mod bench {
 
     #[bench]
     fn rand_exp(bh: &mut BenchHarness) {
-        let mut rng = XorShiftRng::new();
+        let mut rng = XorShiftRng::new().unwrap();
         let mut exp = Exp::new(2.71828 * 3.14159);
 
         bh.iter(|| {
diff --git a/src/librand/distributions/gamma.rs b/src/librand/distributions/gamma.rs
index 029333cd788..70ab4c86455 100644
--- a/src/librand/distributions/gamma.rs
+++ b/src/librand/distributions/gamma.rs
@@ -370,14 +370,14 @@ mod bench {
     use self::test::BenchHarness;
     use std::mem::size_of;
     use distributions::IndependentSample;
-    use {StdRng, RAND_BENCH_N};
+    use {XorShiftRng, RAND_BENCH_N};
     use super::Gamma;
 
 
     #[bench]
     fn bench_gamma_large_shape(bh: &mut BenchHarness) {
         let gamma = Gamma::new(10., 1.0);
-        let mut rng = StdRng::new();
+        let mut rng = XorShiftRng::new().unwrap();
 
         bh.iter(|| {
             for _ in range(0, RAND_BENCH_N) {
@@ -390,7 +390,7 @@ mod bench {
     #[bench]
     fn bench_gamma_small_shape(bh: &mut BenchHarness) {
         let gamma = Gamma::new(0.1, 1.0);
-        let mut rng = StdRng::new();
+        let mut rng = XorShiftRng::new().unwrap();
 
         bh.iter(|| {
             for _ in range(0, RAND_BENCH_N) {
diff --git a/src/librand/distributions/normal.rs b/src/librand/distributions/normal.rs
index 4c9567efc6e..e163714b005 100644
--- a/src/librand/distributions/normal.rs
+++ b/src/librand/distributions/normal.rs
@@ -193,7 +193,7 @@ mod bench {
 
     #[bench]
     fn rand_normal(bh: &mut BenchHarness) {
-        let mut rng = XorShiftRng::new();
+        let mut rng = XorShiftRng::new().unwrap();
         let mut normal = Normal::new(-2.71828, 3.14159);
 
         bh.iter(|| {
diff --git a/src/librand/isaac.rs b/src/librand/isaac.rs
index 5021675c2d8..f985935e07b 100644
--- a/src/librand/isaac.rs
+++ b/src/librand/isaac.rs
@@ -11,6 +11,7 @@
 //! The ISAAC random number generator.
 
 use {Rng, SeedableRng, OSRng};
+use std::io::IoResult;
 use std::iter::{range_step, Repeat};
 use std::slice::raw;
 use std::mem;
@@ -44,12 +45,13 @@ static EMPTY: IsaacRng = IsaacRng {
 
 impl IsaacRng {
     /// Create an ISAAC random number generator with a random seed.
-    pub fn new() -> IsaacRng {
+    ///
+    /// This reads randomness from the operating system (via `OSRng`)
+    /// which may fail, any error is propagated via the `IoResult`
+    /// return value.
+    pub fn new() -> IoResult<IsaacRng> {
         let mut rng = EMPTY;
-        let mut os_rng = match OSRng::new() {
-            Ok(r) => r,
-            Err(e) => fail!("IsaacRng::new: creating OSRng failed: {}", e)
-        };
+        let mut os_rng = try!(OSRng::new());
         unsafe {
             let ptr = rng.rsl.as_mut_ptr();
 
@@ -59,7 +61,7 @@ impl IsaacRng {
         }
 
         rng.init(true);
-        rng
+        Ok(rng)
     }
 
     /// Create an ISAAC random number generator using the default
@@ -252,12 +254,14 @@ static EMPTY_64: Isaac64Rng = Isaac64Rng {
 impl Isaac64Rng {
     /// Create a 64-bit ISAAC random number generator with a random
     /// seed.
-    pub fn new() -> Isaac64Rng {
+    ///
+    /// This reads randomness from the operating system (via `OSRng`)
+    /// which may fail, any error is propagated via the `IoResult`
+    /// return value.
+    pub fn new() -> IoResult<Isaac64Rng> {
         let mut rng = EMPTY_64;
-        let mut os_rng = match OSRng::new() {
-            Ok(r) => r,
-            Err(e) => fail!("Isaac64Rng::new: creating OSRng failed: {}", e)
-        };
+        let mut os_rng = try!(OSRng::new());
+
         unsafe {
             let ptr = rng.rsl.as_mut_ptr();
 
@@ -267,7 +271,7 @@ impl Isaac64Rng {
         }
 
         rng.init(true);
-        rng
+        Ok(rng)
     }
 
     /// Create a 64-bit ISAAC random number generator using the
@@ -436,19 +440,19 @@ impl<'a> SeedableRng<&'a [u64]> for Isaac64Rng {
 #[cfg(test)]
 mod test {
     use super::{IsaacRng, Isaac64Rng};
-    use {Rng, SeedableRng, OSRng};
+    use {Rng, SeedableRng, task_rng};
     use std::slice;
 
     #[test]
     fn test_rng_32_rand_seeded() {
-        let s = OSRng::new().gen_vec::<u32>(256);
+        let s = task_rng().gen_vec::<u32>(256);
         let mut ra: IsaacRng = SeedableRng::from_seed(s.as_slice());
         let mut rb: IsaacRng = SeedableRng::from_seed(s.as_slice());
         assert_eq!(ra.gen_ascii_str(100u), rb.gen_ascii_str(100u));
     }
     #[test]
     fn test_rng_64_rand_seeded() {
-        let s = OSRng::new().gen_vec::<u64>(256);
+        let s = task_rng().gen_vec::<u64>(256);
         let mut ra: Isaac64Rng = SeedableRng::from_seed(s.as_slice());
         let mut rb: Isaac64Rng = SeedableRng::from_seed(s.as_slice());
         assert_eq!(ra.gen_ascii_str(100u), rb.gen_ascii_str(100u));
@@ -471,7 +475,7 @@ mod test {
 
     #[test]
     fn test_rng_32_reseed() {
-        let s = OSRng::new().gen_vec::<u32>(256);
+        let s = task_rng().gen_vec::<u32>(256);
         let mut r: IsaacRng = SeedableRng::from_seed(s.as_slice());
         let string1 = r.gen_ascii_str(100);
 
@@ -482,7 +486,7 @@ mod test {
     }
     #[test]
     fn test_rng_64_reseed() {
-        let s = OSRng::new().gen_vec::<u64>(256);
+        let s = task_rng().gen_vec::<u64>(256);
         let mut r: Isaac64Rng = SeedableRng::from_seed(s.as_slice());
         let string1 = r.gen_ascii_str(100);
 
diff --git a/src/librand/lib.rs b/src/librand/lib.rs
index 438075998f7..7924f438769 100644
--- a/src/librand/lib.rs
+++ b/src/librand/lib.rs
@@ -76,6 +76,7 @@ println!("{:?}", tuple_ptr)
 #[phase(syntax, link)] extern crate log;
 
 use std::cast;
+use std::io::IoResult;
 use std::kinds::marker;
 use std::local_data;
 use std::str;
@@ -401,7 +402,7 @@ pub trait SeedableRng<Seed>: Rng {
 /// appropriate.
 #[deprecated="use `task_rng` or `StdRng::new`"]
 pub fn rng() -> StdRng {
-    StdRng::new()
+    StdRng::new().unwrap()
 }
 
 /// The standard RNG. This is designed to be efficient on the current
@@ -423,9 +424,12 @@ impl StdRng {
     /// number of random numbers, or doesn't need the utmost speed for
     /// generating each number, `task_rng` and/or `random` may be more
     /// appropriate.
+    ///
+    /// Reading the randomness from the OS may fail, and any error is
+    /// propagated via the `IoResult` return value.
     #[cfg(not(target_word_size="64"))]
-    pub fn new() -> StdRng {
-        StdRng { rng: IsaacRng::new() }
+    pub fn new() -> IoResult<StdRng> {
+        IsaacRng::new().map(|r| StdRng { rng: r })
     }
     /// Create a randomly seeded instance of `StdRng`.
     ///
@@ -435,9 +439,12 @@ impl StdRng {
     /// number of random numbers, or doesn't need the utmost speed for
     /// generating each number, `task_rng` and/or `random` may be more
     /// appropriate.
+    ///
+    /// Reading the randomness from the OS may fail, and any error is
+    /// propagated via the `IoResult` return value.
     #[cfg(target_word_size="64")]
-    pub fn new() -> StdRng {
-        StdRng { rng: Isaac64Rng::new() }
+    pub fn new() -> IoResult<StdRng> {
+        Isaac64Rng::new().map(|r| StdRng { rng: r })
     }
 }
 
@@ -475,7 +482,10 @@ impl<'a> SeedableRng<&'a [uint]> for StdRng {
 /// This will read randomness from the operating system to seed the
 /// generator.
 pub fn weak_rng() -> XorShiftRng {
-    XorShiftRng::new()
+    match XorShiftRng::new() {
+        Ok(r) => r,
+        Err(e) => fail!("weak_rng: failed to create seeded RNG: {}", e)
+    }
 }
 
 /// An Xorshift[1] random number
@@ -537,13 +547,10 @@ impl SeedableRng<[u32, .. 4]> for XorShiftRng {
 
 impl XorShiftRng {
     /// Create an xor shift random number generator with a random seed.
-    pub fn new() -> XorShiftRng {
+    pub fn new() -> IoResult<XorShiftRng> {
         let mut s = [0u8, ..16];
+        let mut r = try!(OSRng::new());
         loop {
-            let mut r = match OSRng::new() {
-                Ok(r) => r,
-                Err(e) => fail!("XorShiftRng::new: creating OSRng failed: {}", e)
-            };
             r.fill_bytes(s);
 
             if !s.iter().all(|x| *x == 0) {
@@ -551,7 +558,7 @@ impl XorShiftRng {
             }
         }
         let s: [u32, ..4] = unsafe { cast::transmute(s) };
-        SeedableRng::from_seed(s)
+        Ok(SeedableRng::from_seed(s))
     }
 }
 
@@ -560,7 +567,10 @@ struct TaskRngReseeder;
 
 impl reseeding::Reseeder<StdRng> for TaskRngReseeder {
     fn reseed(&mut self, rng: &mut StdRng) {
-        *rng = StdRng::new();
+        *rng = match StdRng::new() {
+            Ok(r) => r,
+            Err(e) => fail!("could not reseed task_rng: {}", e)
+        }
     }
 }
 static TASK_RNG_RESEED_THRESHOLD: uint = 32_768;
@@ -597,7 +607,11 @@ local_data_key!(TASK_RNG_KEY: ~TaskRngInner)
 pub fn task_rng() -> TaskRng {
     local_data::get_mut(TASK_RNG_KEY, |rng| match rng {
         None => {
-            let mut rng = ~reseeding::ReseedingRng::new(StdRng::new(),
+            let r = match StdRng::new() {
+                Ok(r) => r,
+                Err(e) => fail!("could not initialize task_rng: {}", e)
+            };
+            let mut rng = ~reseeding::ReseedingRng::new(r,
                                                         TASK_RNG_RESEED_THRESHOLD,
                                                         TaskRngReseeder);
             let ptr = &mut *rng as *mut TaskRngInner;
@@ -680,7 +694,7 @@ pub struct Closed01<F>(F);
 #[cfg(test)]
 mod test {
     use std::slice;
-    use super::{Rng, task_rng, random, OSRng, SeedableRng, StdRng};
+    use super::{Rng, task_rng, random, SeedableRng, StdRng};
 
     struct ConstRng { i: u64 }
     impl Rng for ConstRng {
@@ -842,7 +856,7 @@ mod test {
 
     #[test]
     fn test_std_rng_seeded() {
-        let s = OSRng::new().gen_vec::<uint>(256);
+        let s = task_rng().gen_vec::<uint>(256);
         let mut ra: StdRng = SeedableRng::from_seed(s.as_slice());
         let mut rb: StdRng = SeedableRng::from_seed(s.as_slice());
         assert_eq!(ra.gen_ascii_str(100u), rb.gen_ascii_str(100u));
@@ -850,7 +864,7 @@ mod test {
 
     #[test]
     fn test_std_rng_reseed() {
-        let s = OSRng::new().gen_vec::<uint>(256);
+        let s = task_rng().gen_vec::<uint>(256);
         let mut r: StdRng = SeedableRng::from_seed(s.as_slice());
         let string1 = r.gen_ascii_str(100);
 
@@ -873,7 +887,7 @@ mod bench {
 
     #[bench]
     fn rand_xorshift(bh: &mut BenchHarness) {
-        let mut rng = XorShiftRng::new();
+        let mut rng = XorShiftRng::new().unwrap();
         bh.iter(|| {
             for _ in range(0, RAND_BENCH_N) {
                 rng.gen::<uint>();
@@ -884,7 +898,7 @@ mod bench {
 
     #[bench]
     fn rand_isaac(bh: &mut BenchHarness) {
-        let mut rng = IsaacRng::new();
+        let mut rng = IsaacRng::new().unwrap();
         bh.iter(|| {
             for _ in range(0, RAND_BENCH_N) {
                 rng.gen::<uint>();
@@ -895,7 +909,7 @@ mod bench {
 
     #[bench]
     fn rand_isaac64(bh: &mut BenchHarness) {
-        let mut rng = Isaac64Rng::new();
+        let mut rng = Isaac64Rng::new().unwrap();
         bh.iter(|| {
             for _ in range(0, RAND_BENCH_N) {
                 rng.gen::<uint>();
@@ -906,7 +920,7 @@ mod bench {
 
     #[bench]
     fn rand_std(bh: &mut BenchHarness) {
-        let mut rng = StdRng::new();
+        let mut rng = StdRng::new().unwrap();
         bh.iter(|| {
             for _ in range(0, RAND_BENCH_N) {
                 rng.gen::<uint>();
@@ -917,7 +931,7 @@ mod bench {
 
     #[bench]
     fn rand_shuffle_100(bh: &mut BenchHarness) {
-        let mut rng = XorShiftRng::new();
+        let mut rng = XorShiftRng::new().unwrap();
         let x : &mut[uint] = [1,..100];
         bh.iter(|| {
             rng.shuffle_mut(x);
diff --git a/src/librand/os.rs b/src/librand/os.rs
index 396346b672f..fc0944fc7db 100644
--- a/src/librand/os.rs
+++ b/src/librand/os.rs
@@ -192,7 +192,7 @@ mod test {
 
     #[test]
     fn test_os_rng() {
-        let mut r = OSRng::new();
+        let mut r = OSRng::new().unwrap();
 
         r.next_u32();
         r.next_u64();
@@ -214,7 +214,7 @@ mod test {
 
                 // deschedule to attempt to interleave things as much
                 // as possible (XXX: is this a good test?)
-                let mut r = OSRng::new();
+                let mut r = OSRng::new().unwrap();
                 task::deschedule();
                 let mut v = [0u8, .. 1000];
 
diff --git a/src/librand/reseeding.rs b/src/librand/reseeding.rs
index a64124e637e..131f081cba7 100644
--- a/src/librand/reseeding.rs
+++ b/src/librand/reseeding.rs
@@ -100,12 +100,12 @@ impl<S, R: SeedableRng<S>, Rsdr: Reseeder<R>>
 /// # Example
 ///
 /// ```rust
-/// use rand::{Rng, SeedableRng};
+/// use rand::{Rng, SeedableRng, StdRng};
 /// use rand::reseeding::{Reseeder, ReseedingRng};
 ///
 /// struct TickTockReseeder { tick: bool }
-/// impl Reseeder<rand::StdRng> for TickTockReseeder {
-///     fn reseed(&mut self, rng: &mut rand::StdRng) {
+/// impl Reseeder<StdRng> for TickTockReseeder {
+///     fn reseed(&mut self, rng: &mut StdRng) {
 ///         let val = if self.tick {0} else {1};
 ///         rng.reseed(&[val]);
 ///         self.tick = !self.tick;
@@ -113,7 +113,9 @@ impl<S, R: SeedableRng<S>, Rsdr: Reseeder<R>>
 /// }
 /// fn main() {
 ///     let rsdr = TickTockReseeder { tick: true };
-///     let mut rng = ReseedingRng::new(rand::StdRng::new(), 10, rsdr);
+///
+///     let inner = StdRng::new().unwrap();
+///     let mut rng = ReseedingRng::new(inner, 10, rsdr);
 ///
 ///     // this will repeat, because it gets reseeded very regularly.
 ///     println!("{}", rng.gen_ascii_str(100));
diff --git a/src/libstd/fmt/num.rs b/src/libstd/fmt/num.rs
index 4b35a7596c9..85fffc5545a 100644
--- a/src/libstd/fmt/num.rs
+++ b/src/libstd/fmt/num.rs
@@ -400,31 +400,31 @@ mod bench {
 
         #[bench]
         fn format_bin(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { format!("{:t}", rng.gen::<uint>()); })
         }
 
         #[bench]
         fn format_oct(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { format!("{:o}", rng.gen::<uint>()); })
         }
 
         #[bench]
         fn format_dec(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { format!("{:u}", rng.gen::<uint>()); })
         }
 
         #[bench]
         fn format_hex(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { format!("{:x}", rng.gen::<uint>()); })
         }
 
         #[bench]
         fn format_base_36(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { format!("{}", radix(rng.gen::<uint>(), 36)); })
         }
     }
@@ -436,31 +436,31 @@ mod bench {
 
         #[bench]
         fn format_bin(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { format!("{:t}", rng.gen::<int>()); })
         }
 
         #[bench]
         fn format_oct(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { format!("{:o}", rng.gen::<int>()); })
         }
 
         #[bench]
         fn format_dec(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { format!("{:d}", rng.gen::<int>()); })
         }
 
         #[bench]
         fn format_hex(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { format!("{:x}", rng.gen::<int>()); })
         }
 
         #[bench]
         fn format_base_36(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { format!("{}", radix(rng.gen::<int>(), 36)); })
         }
     }
diff --git a/src/libstd/io/fs.rs b/src/libstd/io/fs.rs
index e66aa8c0046..63973584c1e 100644
--- a/src/libstd/io/fs.rs
+++ b/src/libstd/io/fs.rs
@@ -1285,7 +1285,7 @@ mod test {
         use rand::{StdRng, Rng};
 
         let mut bytes = [0, ..1024];
-        StdRng::new().fill_bytes(bytes);
+        StdRng::new().unwrap().fill_bytes(bytes);
 
         let tmpdir = tmpdir();
 
diff --git a/src/libstd/num/strconv.rs b/src/libstd/num/strconv.rs
index 9f9a9ec8e2e..c516973ddd5 100644
--- a/src/libstd/num/strconv.rs
+++ b/src/libstd/num/strconv.rs
@@ -821,31 +821,31 @@ mod bench {
 
         #[bench]
         fn to_str_bin(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { rng.gen::<uint>().to_str_radix(2); })
         }
 
         #[bench]
         fn to_str_oct(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { rng.gen::<uint>().to_str_radix(8); })
         }
 
         #[bench]
         fn to_str_dec(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { rng.gen::<uint>().to_str_radix(10); })
         }
 
         #[bench]
         fn to_str_hex(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { rng.gen::<uint>().to_str_radix(16); })
         }
 
         #[bench]
         fn to_str_base_36(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { rng.gen::<uint>().to_str_radix(36); })
         }
     }
@@ -857,31 +857,31 @@ mod bench {
 
         #[bench]
         fn to_str_bin(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { rng.gen::<int>().to_str_radix(2); })
         }
 
         #[bench]
         fn to_str_oct(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { rng.gen::<int>().to_str_radix(8); })
         }
 
         #[bench]
         fn to_str_dec(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { rng.gen::<int>().to_str_radix(10); })
         }
 
         #[bench]
         fn to_str_hex(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { rng.gen::<int>().to_str_radix(16); })
         }
 
         #[bench]
         fn to_str_base_36(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { rng.gen::<int>().to_str_radix(36); })
         }
     }
@@ -893,7 +893,7 @@ mod bench {
 
         #[bench]
         fn float_to_str(bh: &mut BenchHarness) {
-            let mut rng = XorShiftRng::new();
+            let mut rng = XorShiftRng::new().unwrap();
             bh.iter(|| { f64::to_str(rng.gen()); })
         }
     }
diff --git a/src/libstd/rt/task.rs b/src/libstd/rt/task.rs
index ededc69c5a1..abaa91b12f8 100644
--- a/src/libstd/rt/task.rs
+++ b/src/libstd/rt/task.rs
@@ -434,7 +434,7 @@ mod test {
     #[test]
     fn rng() {
         use rand::{StdRng, Rng};
-        let mut r = StdRng::new();
+        let mut r = StdRng::new().unwrap();
         let _ = r.next_u32();
     }
 
diff --git a/src/test/bench/noise.rs b/src/test/bench/noise.rs
index 4954f083b36..babf3f737fb 100644
--- a/src/test/bench/noise.rs
+++ b/src/test/bench/noise.rs
@@ -41,7 +41,7 @@ struct Noise2DContext {
 
 impl Noise2DContext {
     fn new() -> Noise2DContext {
-        let mut rng = StdRng::new();
+        let mut rng = StdRng::new().unwrap();
 
         let mut rgradients = [Vec2 { x: 0.0, y: 0.0 }, ..256];
         for x in rgradients.mut_iter() {