Rename flag, datastructure and messaging around muting stdout and stderr

src/bin/miri.rs

@@ -374,8 +374,8 @@ fn main() {
                     miri_config.tag_raw = true;
                     miri_config.check_number_validity = true;
                 }
-                "-Zmiri-drop-stdout-stderr" => {
-                    miri_config.drop_stdout_stderr = true;
+                "-Zmiri-mute-stdout-stderr" => {
+                    miri_config.mute_stdout_stderr = true;
                 }
                 "-Zmiri-track-raw-pointers" => {
                     eprintln!(

src/eval.rs

@@ -118,7 +118,7 @@ pub struct MiriConfig {
     pub strict_provenance: bool,
     /// Whether to ignore any output by the program. This is helpful when debugging miri
     /// as its messages don't get intermingled with the program messages.
-    pub drop_stdout_stderr: bool,
+    pub mute_stdout_stderr: bool,
 }
 
 impl Default for MiriConfig {
@@ -145,7 +145,7 @@ impl Default for MiriConfig {
             panic_on_unsupported: false,
             backtrace_style: BacktraceStyle::Short,
             strict_provenance: false,
-            drop_stdout_stderr: false,
+            mute_stdout_stderr: false,
         }
     }
 }

src/machine.rs

@@ -292,8 +292,8 @@ pub struct Evaluator<'mir, 'tcx> {
     /// Failure rate of compare_exchange_weak, between 0.0 and 1.0
     pub(crate) cmpxchg_weak_failure_rate: f64,
 
-    /// Corresponds to -Zmiri-drop-stdout-stderr and doesn't write the output but acts as if it succeeded.
-    pub(crate) drop_stdout_stderr: bool,
+    /// Corresponds to -Zmiri-mute-stdout-stderr and doesn't write the output but acts as if it succeeded.
+    pub(crate) mute_stdout_stderr: bool,
 }
 
 impl<'mir, 'tcx> Evaluator<'mir, 'tcx> {
@@ -330,7 +330,7 @@ impl<'mir, 'tcx> Evaluator<'mir, 'tcx> {
             validate: config.validate,
             enforce_number_validity: config.check_number_validity,
             enforce_abi: config.check_abi,
-            file_handler: FileHandler::new(config.drop_stdout_stderr),
+            file_handler: FileHandler::new(config.mute_stdout_stderr),
             dir_handler: Default::default(),
             time_anchor: Instant::now(),
             layouts,
@@ -347,7 +347,7 @@ impl<'mir, 'tcx> Evaluator<'mir, 'tcx> {
             tracked_alloc_ids: config.tracked_alloc_ids.clone(),
             check_alignment: config.check_alignment,
             cmpxchg_weak_failure_rate: config.cmpxchg_weak_failure_rate,
-            drop_stdout_stderr: config.drop_stdout_stderr,
+            mute_stdout_stderr: config.mute_stdout_stderr,
         }
     }
 

src/shims/posix/fs.rs

@@ -252,11 +252,11 @@ impl FileDescriptor for io::Stderr {
 }
 
 #[derive(Debug)]
-struct DevNull;
+struct DummyOutput;
 
-impl FileDescriptor for DevNull {
+impl FileDescriptor for DummyOutput {
     fn as_file_handle<'tcx>(&self) -> InterpResult<'tcx, &FileHandle> {
-        throw_unsup_format!("/dev/null cannot be used as FileHandle");
+        throw_unsup_format!("stderr and stdout cannot be used as FileHandle");
     }
 
     fn read<'tcx>(
@@ -264,7 +264,7 @@ impl FileDescriptor for DevNull {
         _communicate_allowed: bool,
         _bytes: &mut [u8],
     ) -> InterpResult<'tcx, io::Result<usize>> {
-        throw_unsup_format!("cannot read from /dev/null");
+        throw_unsup_format!("cannot read from stderr or stdout");
     }
 
     fn write<'tcx>(
@@ -272,7 +272,7 @@ impl FileDescriptor for DevNull {
         _communicate_allowed: bool,
         bytes: &[u8],
     ) -> InterpResult<'tcx, io::Result<usize>> {
-        // We just don't write anything
+        // We just don't write anything, but report to the user that we did.
         Ok(Ok(bytes.len()))
     }
 
@@ -281,18 +281,18 @@ impl FileDescriptor for DevNull {
         _communicate_allowed: bool,
         _offset: SeekFrom,
     ) -> InterpResult<'tcx, io::Result<u64>> {
-        throw_unsup_format!("cannot seek on /dev/null");
+        throw_unsup_format!("cannot seek on stderr or stdout");
     }
 
     fn close<'tcx>(
         self: Box<Self>,
         _communicate_allowed: bool,
     ) -> InterpResult<'tcx, io::Result<i32>> {
-        throw_unsup_format!("/dev/null cannot be closed");
+        throw_unsup_format!("stderr and stdout cannot be closed");
     }
 
     fn dup<'tcx>(&mut self) -> io::Result<Box<dyn FileDescriptor>> {
-        Ok(Box::new(DevNull))
+        Ok(Box::new(DummyOutput))
     }
 }
 
@@ -302,11 +302,11 @@ pub struct FileHandler {
 }
 
 impl<'tcx> FileHandler {
-    pub(crate) fn new(drop_stdout_stderr: bool) -> FileHandler {
+    pub(crate) fn new(mute_stdout_stderr: bool) -> FileHandler {
         let mut handles: BTreeMap<_, Box<dyn FileDescriptor>> = BTreeMap::new();
-        if drop_stdout_stderr {
-            handles.insert(0i32, Box::new(DevNull));
-            handles.insert(1i32, Box::new(DevNull));
+        if mute_stdout_stderr {
+            handles.insert(0i32, Box::new(DummyOutput));
+            handles.insert(1i32, Box::new(DummyOutput));
         } else {
             handles.insert(0i32, Box::new(io::stdin()));
             handles.insert(1i32, Box::new(io::stdout()));

src/shims/windows/dlsym.rs

@@ -75,7 +75,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                     use std::io::{self, Write};
 
                     let buf_cont = this.read_bytes_ptr(buf, Size::from_bytes(u64::from(n)))?;
-                    let res = if this.machine.drop_stdout_stderr {
+                    let res = if this.machine.mute_stdout_stderr {
                         Ok(buf_cont.len())
                     } else if handle == -11 {
                         io::stdout().write(buf_cont)

tests/run-pass/hide_stdout.rs

@@ -1,4 +1,4 @@
-// compile-flags: -Zmiri-drop-stdout-stderr
+// compile-flags: -Zmiri-mute-stdout-stderr
 
 fn main() {
     println!("cake");