tell people how to set miri flags

Author: RalfJung

src/tools/miri/cargo-miri/src/phases.rs

@@ -23,6 +23,12 @@ Subcommands:
     clean                    Clean the Miri cache & target directory
 
 The cargo options are exactly the same as for `cargo run` and `cargo test`, respectively.
+Furthermore, the following extra flags and environment variables are recognized for `run` and `test`:
+
+    --many-seeds[=from..to]  Run the program/tests many times with different seeds in the given range.
+                             The range defaults to `0..64`.
+
+    MIRIFLAGS                Extra flags to pass to the Miri driver. Use this to pass `-Zmiri-...` flags.
 
 Examples:
     cargo miri run

src/tools/miri/src/diagnostics.rs

@@ -227,8 +227,8 @@ pub fn report_error<'tcx>(
         let helps = match info {
             UnsupportedInIsolation(_) =>
                 vec![
-                    (None, format!("pass the flag `-Zmiri-disable-isolation` to disable isolation;")),
-                    (None, format!("or pass `-Zmiri-isolation-error=warn` to configure Miri to return an error code from isolated operations (if supported for that operation) and continue with a warning")),
+                    (None, format!("set `MIRIFLAGS=-Zmiri-disable-isolation` to disable isolation;")),
+                    (None, format!("or set `MIRIFLAGS=-Zmiri-isolation-error=warn` to make Miri return an error code from isolated operations (if supported for that operation) and continue with a warning")),
                 ],
             UnsupportedForeignItem(_) => {
                 vec![
@@ -463,19 +463,22 @@ pub fn report_leaks<'tcx>(
 ) {
     let mut any_pruned = false;
     for (id, kind, mut alloc) in leaks {
+        let mut title = format!(
+            "memory leaked: {id:?} ({}, size: {:?}, align: {:?})",
+            kind,
+            alloc.size().bytes(),
+            alloc.align.bytes()
+        );
         let Some(backtrace) = alloc.extra.backtrace.take() else {
+            ecx.tcx.dcx().err(title);
             continue;
         };
+        title.push_str(", allocated here:");
         let (backtrace, pruned) = prune_stacktrace(backtrace, &ecx.machine);
         any_pruned |= pruned;
         report_msg(
             DiagLevel::Error,
-            format!(
-                "memory leaked: {id:?} ({}, size: {:?}, align: {:?}), allocated here:",
-                kind,
-                alloc.size().bytes(),
-                alloc.align.bytes()
-            ),
+            title,
             vec![],
             vec![],
             vec![],
@@ -642,13 +645,9 @@ impl<'tcx> MiriMachine<'tcx> {
                     (
                         None,
                         format!(
-                            "This program is using integer-to-pointer casts or (equivalently) `ptr::with_exposed_provenance`,"
+                            "This program is using integer-to-pointer casts or (equivalently) `ptr::with_exposed_provenance`, which means that Miri might miss pointer bugs in this program."
                         ),
                     ),
-                    (
-                        None,
-                        format!("which means that Miri might miss pointer bugs in this program."),
-                    ),
                     (
                         None,
                         format!(
@@ -664,13 +663,13 @@ impl<'tcx> MiriMachine<'tcx> {
                     (
                         None,
                         format!(
-                            "You can then pass the `-Zmiri-strict-provenance` flag to Miri, to ensure you are not relying on `with_exposed_provenance` semantics."
+                            "You can then set `MIRIFLAGS=-Zmiri-strict-provenance` to ensure you are not relying on `with_exposed_provenance` semantics."
                         ),
                     ),
                     (
                         None,
                         format!(
-                            "Alternatively, the `-Zmiri-permissive-provenance` flag disables this warning."
+                            "Alternatively, `MIRIFLAGS=-Zmiri-permissive-provenance` disables this warning."
                         ),
                     ),
                 ],

src/tools/miri/src/eval.rs

@@ -468,22 +468,15 @@ pub fn eval_entry<'tcx>(
         // Check for thread leaks.
         if !ecx.have_all_terminated() {
             tcx.dcx().err("the main thread terminated without waiting for all remaining threads");
-            tcx.dcx().note("pass `-Zmiri-ignore-leaks` to disable this check");
+            tcx.dcx().note("set `MIRIFLAGS=-Zmiri-ignore-leaks` to disable this check");
             return None;
         }
         // Check for memory leaks.
         info!("Additional static roots: {:?}", ecx.machine.static_roots);
         let leaks = ecx.find_leaked_allocations(&ecx.machine.static_roots);
         if !leaks.is_empty() {
             report_leaks(&ecx, leaks);
-            let leak_message = "the evaluated program leaked memory, pass `-Zmiri-ignore-leaks` to disable this check";
-            if ecx.machine.collect_leak_backtraces {
-                // If we are collecting leak backtraces, each leak is a distinct error diagnostic.
-                tcx.dcx().note(leak_message);
-            } else {
-                // If we do not have backtraces, we just report an error without any span.
-                tcx.dcx().err(leak_message);
-            };
+            tcx.dcx().note("set `MIRIFLAGS=-Zmiri-ignore-leaks` to disable this check");
             // Ignore the provided return code - let the reported error
             // determine the return code.
             return None;

src/tools/miri/tests/fail-dep/concurrency/libc_pthread_create_main_terminate.stderr

@@ -1,6 +1,6 @@
 error: the main thread terminated without waiting for all remaining threads
 
-note: pass `-Zmiri-ignore-leaks` to disable this check
+note: set `MIRIFLAGS=-Zmiri-ignore-leaks` to disable this check
 
 error: aborting due to 1 previous error
 

src/tools/miri/tests/fail-dep/libc/aligned_alloc_size_zero_leak.stderr

@@ -9,7 +9,7 @@ LL |         aligned_alloc(2, 0);
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
-note: the evaluated program leaked memory, pass `-Zmiri-ignore-leaks` to disable this check
+note: set `MIRIFLAGS=-Zmiri-ignore-leaks` to disable this check
 
 error: aborting due to 1 previous error
 

src/tools/miri/tests/fail-dep/libc/fs/isolated_stdin.stderr

@@ -4,8 +4,8 @@ error: unsupported operation: `read` from stdin not available when isolation is
 LL |         libc::read(0, bytes.as_mut_ptr() as *mut libc::c_void, 512);
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `read` from stdin not available when isolation is enabled
    |
-   = help: pass the flag `-Zmiri-disable-isolation` to disable isolation;
-   = help: or pass `-Zmiri-isolation-error=warn` to configure Miri to return an error code from isolated operations (if supported for that operation) and continue with a warning
+   = help: set `MIRIFLAGS=-Zmiri-disable-isolation` to disable isolation;
+   = help: or set `MIRIFLAGS=-Zmiri-isolation-error=warn` to make Miri return an error code from isolated operations (if supported for that operation) and continue with a warning
    = note: BACKTRACE:
    = note: inside `main` at $DIR/isolated_stdin.rs:LL:CC
 

src/tools/miri/tests/fail-dep/libc/malloc_zero_memory_leak.stderr

@@ -9,7 +9,7 @@ LL |         let _ptr = libc::malloc(0);
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
-note: the evaluated program leaked memory, pass `-Zmiri-ignore-leaks` to disable this check
+note: set `MIRIFLAGS=-Zmiri-ignore-leaks` to disable this check
 
 error: aborting due to 1 previous error
 

src/tools/miri/tests/fail-dep/libc/posix_memalign_size_zero_leak.stderr

@@ -9,7 +9,7 @@ LL |     let _ = unsafe { libc::posix_memalign(&mut ptr, align, size) };
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
-note: the evaluated program leaked memory, pass `-Zmiri-ignore-leaks` to disable this check
+note: set `MIRIFLAGS=-Zmiri-ignore-leaks` to disable this check
 
 error: aborting due to 1 previous error
 

src/tools/miri/tests/fail/intrinsics/ptr_metadata_uninit_slice_len.stderr

@@ -4,12 +4,11 @@ warning: integer-to-pointer cast
 LL |         (*p.as_mut_ptr().cast::<[*const i32; 2]>())[0] = 4 as *const i32;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ integer-to-pointer cast
    |
-   = help: This program is using integer-to-pointer casts or (equivalently) `ptr::with_exposed_provenance`,
-   = help: which means that Miri might miss pointer bugs in this program.
+   = help: This program is using integer-to-pointer casts or (equivalently) `ptr::with_exposed_provenance`, which means that Miri might miss pointer bugs in this program.
    = help: See https://doc.rust-lang.org/nightly/std/ptr/fn.with_exposed_provenance.html for more details on that operation.
    = help: To ensure that Miri does not miss bugs in your program, use Strict Provenance APIs (https://doc.rust-lang.org/nightly/std/ptr/index.html#strict-provenance, https://crates.io/crates/sptr) instead.
-   = help: You can then pass the `-Zmiri-strict-provenance` flag to Miri, to ensure you are not relying on `with_exposed_provenance` semantics.
-   = help: Alternatively, the `-Zmiri-permissive-provenance` flag disables this warning.
+   = help: You can then set `MIRIFLAGS=-Zmiri-strict-provenance` to ensure you are not relying on `with_exposed_provenance` semantics.
+   = help: Alternatively, `MIRIFLAGS=-Zmiri-permissive-provenance` disables this warning.
    = note: BACKTRACE:
    = note: inside `main` at $DIR/ptr_metadata_uninit_slice_len.rs:LL:CC
 

src/tools/miri/tests/fail/memleak.stderr

@@ -18,7 +18,7 @@ LL |     std::mem::forget(Box::new(42));
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
-note: the evaluated program leaked memory, pass `-Zmiri-ignore-leaks` to disable this check
+note: set `MIRIFLAGS=-Zmiri-ignore-leaks` to disable this check
 
 error: aborting due to 1 previous error