6 files changed, 22 insertions, 2 deletions
diff --git a/src/libstd/sys/cloudabi/stdio.rs b/src/libstd/sys/cloudabi/stdio.rs
index 9519a926471..1d7344f921c 100644
--- a/src/libstd/sys/cloudabi/stdio.rs
+++ b/src/libstd/sys/cloudabi/stdio.rs
@@ -77,3 +77,7 @@ pub fn is_ebadf(err: &io::Error) -> bool {
 }
 
 pub const STDIN_BUF_SIZE: usize = ::sys_common::io::DEFAULT_BUF_SIZE;
+
+pub fn stderr_prints_nothing() -> bool {
+    false
+}
diff --git a/src/libstd/sys/redox/stdio.rs b/src/libstd/sys/redox/stdio.rs
index 3abb094ac34..7a4d11b0ecb 100644
--- a/src/libstd/sys/redox/stdio.rs
+++ b/src/libstd/sys/redox/stdio.rs
@@ -75,3 +75,7 @@ pub fn is_ebadf(err: &io::Error) -> bool {
 }
 
 pub const STDIN_BUF_SIZE: usize = ::sys_common::io::DEFAULT_BUF_SIZE;
+
+pub fn stderr_prints_nothing() -> bool {
+    false
+}
diff --git a/src/libstd/sys/unix/stdio.rs b/src/libstd/sys/unix/stdio.rs
index e9b3d4affc7..87ba2aef4f1 100644
--- a/src/libstd/sys/unix/stdio.rs
+++ b/src/libstd/sys/unix/stdio.rs
@@ -75,3 +75,7 @@ pub fn is_ebadf(err: &io::Error) -> bool {
 }
 
 pub const STDIN_BUF_SIZE: usize = ::sys_common::io::DEFAULT_BUF_SIZE;
+
+pub fn stderr_prints_nothing() -> bool {
+    false
+}
diff --git a/src/libstd/sys/wasm/rwlock.rs b/src/libstd/sys/wasm/rwlock.rs
index 8b06f541674..6516010af47 100644
--- a/src/libstd/sys/wasm/rwlock.rs
+++ b/src/libstd/sys/wasm/rwlock.rs
@@ -30,7 +30,7 @@ impl RWLock {
         if *mode >= 0 {
             *mode += 1;
         } else {
-            panic!("rwlock locked for writing");
+            rtabort!("rwlock locked for writing");
         }
     }
 
@@ -51,7 +51,7 @@ impl RWLock {
         if *mode == 0 {
             *mode = -1;
         } else {
-            panic!("rwlock locked for reading")
+            rtabort!("rwlock locked for reading")
         }
     }
 
diff --git a/src/libstd/sys/wasm/stdio.rs b/src/libstd/sys/wasm/stdio.rs
index beb19c0ed2c..023f29576a2 100644
--- a/src/libstd/sys/wasm/stdio.rs
+++ b/src/libstd/sys/wasm/stdio.rs
@@ -69,3 +69,7 @@ pub const STDIN_BUF_SIZE: usize = 0;
 pub fn is_ebadf(_err: &io::Error) -> bool {
     true
 }
+
+pub fn stderr_prints_nothing() -> bool {
+    !cfg!(feature = "wasm_syscall")
+}
diff --git a/src/libstd/sys/windows/stdio.rs b/src/libstd/sys/windows/stdio.rs
index b43df20bddd..81b89da21d3 100644
--- a/src/libstd/sys/windows/stdio.rs
+++ b/src/libstd/sys/windows/stdio.rs
@@ -227,3 +227,7 @@ pub fn is_ebadf(err: &io::Error) -> bool {
 // idea is that on windows we use a slightly smaller buffer that's
 // been seen to be acceptable.
 pub const STDIN_BUF_SIZE: usize = 8 * 1024;
+
+pub fn stderr_prints_nothing() -> bool {
+    false
+}