Auto merge of #1977 - saethlin:short-backtraces, r=RalfJung

Prune backtraces similar to RUST_BACKTRACE=1 logic This removes the majority of output from `cargo miri run` and `cargo miri test` in common usage. ~~I've copied the logic almost directly from `std`: 3b186511f6/library/std/src/sys_common/backtrace.rs (L76-L77~~) ~~It might be nice to have the "some details were omitted" note and a fallback to a setting where we print everything just in case this logic goes sideways, but~~ ~~1. I'm not sure where to put the note~~ ~~2. `MIRI_BACKTRACE`, `RUST_BACKTRACE`, and `RUSTC_CTFE_BACKTRACE` already do something else. Should we repurpose or add on to the semantics of `MIRI_BACKTRACE`?~~ --- Based on this tiny silly crate: ```rust fn main() { some_function(); } fn some_function() { unsafe { let _x: &u8 = core::mem::transmute(1usize); } } #[cfg(test)] mod tests { #[test] fn it_works() { unsafe { let _x: &'static u8 = core::mem::transmute(1usize); } } } ``` `cargo miri run`: Before: ``` Finished dev [unoptimized + debuginfo] target(s) in 0.10s Running `/home/ben/.cargo/bin/cargo-miri target/miri/x86_64-unknown-linux-gnu/debug/scratch` error: Undefined Behavior: type validation failed: encountered a dangling reference (address 0x1 is unallocated) --> src/main.rs:7:23 | 7 | let _x: &u8 = core::mem::transmute(1usize); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a dangling reference (address 0x1 is unallocated) | = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information = note: inside `some_function` at src/main.rs:7:23 note: inside `main` at src/main.rs:2:5 --> src/main.rs:2:5 | 2 | some_function(); | ^^^^^^^^^^^^^^^ = note: inside `<fn() as std::ops::FnOnce<()>>::call_once - shim(fn())` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/core/src/ops/function.rs:227:5 = note: inside `std::sys_common::backtrace::__rust_begin_short_backtrace::<fn(), ()>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/sys_common/backtrace.rs:122:18 = note: inside closure at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/rt.rs:145:18 = note: inside `std::ops::function::impls::<impl std::ops::FnOnce<()> for &dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe>::call_once` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/core/src/ops/function.rs:259:13 = note: inside `std::panicking::r#try::do_call::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panicking.rs:492:40 = note: inside `std::panicking::r#try::<i32, &dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panicking.rs:456:19 = note: inside `std::panic::catch_unwind::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panic.rs:137:14 = note: inside closure at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/rt.rs:128:48 = note: inside `std::panicking::r#try::do_call::<[closure@std::rt::lang_start_internal::{closure#2}], isize>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panicking.rs:492:40 = note: inside `std::panicking::r#try::<isize, [closure@std::rt::lang_start_internal::{closure#2}]>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panicking.rs:456:19 = note: inside `std::panic::catch_unwind::<[closure@std::rt::lang_start_internal::{closure#2}], isize>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panic.rs:137:14 = note: inside `std::rt::lang_start_internal` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/rt.rs:128:20 = note: inside `std::rt::lang_start::<()>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/rt.rs:144:17 error: aborting due to previous error ``` After: ``` Finished dev [unoptimized + debuginfo] target(s) in 0.10s Running `/home/ben/.cargo/bin/cargo-miri target/miri/x86_64-unknown-linux-gnu/debug/scratch` error: Undefined Behavior: type validation failed: encountered a dangling reference (address 0x1 is unallocated) --> src/main.rs:7:23 | 7 | let _x: &u8 = core::mem::transmute(1usize); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a dangling reference (address 0x1 is unallocated) | = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information = note: inside `some_function` at src/main.rs:7:23 note: inside `main` at src/main.rs:2:5 --> src/main.rs:2:5 | 2 | some_function(); | ^^^^^^^^^^^^^^^ note: Some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace. error: aborting due to previous error ``` `cargo miri test` Before: ``` Finished test [unoptimized + debuginfo] target(s) in 0.00s Running unittests (target/miri/x86_64-unknown-linux-gnu/debug/deps/scratch-9d7717efc37bb64c) running 1 test test tests::it_works ... error: Undefined Behavior: type validation failed: encountered a dangling reference (address 0x1 is unallocated) --> src/main.rs:16:35 | 16 | let _x: &'static u8 = core::mem::transmute(1usize); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a dangling reference (address 0x1 is unallocated) | = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information = note: inside `tests::it_works` at src/main.rs:16:35 note: inside closure at src/main.rs:14:5 --> src/main.rs:14:5 | 13 | #[test] | ------- in this procedural macro expansion 14 | / fn it_works() { 15 | | unsafe { 16 | | let _x: &'static u8 = core::mem::transmute(1usize); 17 | | } 18 | | } | |_____^ = note: inside `<[closure@src/main.rs:14:5: 18:6] as std::ops::FnOnce<()>>::call_once - shim` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/core/src/ops/function.rs:227:5 = note: inside `<fn() as std::ops::FnOnce<()>>::call_once - shim(fn())` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/core/src/ops/function.rs:227:5 = note: inside `tests::test::__rust_begin_short_backtrace::<fn()>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/test/src/lib.rs:575:5 = note: inside closure at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/test/src/lib.rs:566:30 = note: inside `<[closure@tests::test::run_test::{closure#1}] as std::ops::FnOnce<()>>::call_once - shim(vtable)` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/core/src/ops/function.rs:227:5 = note: inside `<std::boxed::Box<dyn std::ops::FnOnce() + std::marker::Send> as std::ops::FnOnce<()>>::call_once` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/alloc/src/boxed.rs:1854:9 = note: inside `<std::panic::AssertUnwindSafe<std::boxed::Box<dyn std::ops::FnOnce() + std::marker::Send>> as std::ops::FnOnce<()>>::call_once` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/core/src/panic/unwind_safe.rs:271:9 = note: inside `std::panicking::r#try::do_call::<std::panic::AssertUnwindSafe<std::boxed::Box<dyn std::ops::FnOnce() + std::marker::Send>>, ()>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panicking.rs:492:40 = note: inside `std::panicking::r#try::<(), std::panic::AssertUnwindSafe<std::boxed::Box<dyn std::ops::FnOnce() + std::marker::Send>>>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panicking.rs:456:19 = note: inside `std::panic::catch_unwind::<std::panic::AssertUnwindSafe<std::boxed::Box<dyn std::ops::FnOnce() + std::marker::Send>>, ()>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panic.rs:137:14 = note: inside `tests::test::run_test_in_process` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/test/src/lib.rs:598:18 = note: inside closure at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/test/src/lib.rs:492:39 = note: inside `tests::test::run_test::run_test_inner` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/test/src/lib.rs:530:13 = note: inside `tests::test::run_test` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/test/src/lib.rs:562:28 = note: inside `tests::test::run_tests::<[closure@tests::test::run_tests_console::{closure#2}]>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/test/src/lib.rs:305:17 = note: inside `tests::test::run_tests_console` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/test/src/console.rs:290:5 = note: inside `tests::test::test_main` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/test/src/lib.rs:116:15 = note: inside `tests::test::test_main_static` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/test/src/lib.rs:135:5 = note: inside `main` = note: inside `<fn() as std::ops::FnOnce<()>>::call_once - shim(fn())` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/core/src/ops/function.rs:227:5 = note: inside `std::sys_common::backtrace::__rust_begin_short_backtrace::<fn(), ()>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/sys_common/backtrace.rs:122:18 = note: inside closure at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/rt.rs:145:18 = note: inside `std::ops::function::impls::<impl std::ops::FnOnce<()> for &dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe>::call_once` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/core/src/ops/function.rs:259:13 = note: inside `std::panicking::r#try::do_call::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panicking.rs:492:40 = note: inside `std::panicking::r#try::<i32, &dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panicking.rs:456:19 = note: inside `std::panic::catch_unwind::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panic.rs:137:14 = note: inside closure at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/rt.rs:128:48 = note: inside `std::panicking::r#try::do_call::<[closure@std::rt::lang_start_internal::{closure#2}], isize>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panicking.rs:492:40 = note: inside `std::panicking::r#try::<isize, [closure@std::rt::lang_start_internal::{closure#2}]>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panicking.rs:456:19 = note: inside `std::panic::catch_unwind::<[closure@std::rt::lang_start_internal::{closure#2}], isize>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panic.rs:137:14 = note: inside `std::rt::lang_start_internal` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/rt.rs:128:20 = note: inside `std::rt::lang_start::<()>` at /home/ben/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/rt.rs:144:17 = note: this error originates in the attribute macro `test` (in Nightly builds, run with -Z macro-backtrace for more info) error: aborting due to previous error error: test failed, to rerun pass '--bin scratch' ``` After: ``` Finished test [unoptimized + debuginfo] target(s) in 0.00s Running unittests (target/miri/x86_64-unknown-linux-gnu/debug/deps/scratch-9d7717efc37bb64c) running 1 test test tests::it_works ... error: Undefined Behavior: type validation failed: encountered a dangling reference (address 0x1 is unallocated) --> src/main.rs:16:35 | 16 | let _x: &'static u8 = core::mem::transmute(1usize); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a dangling reference (address 0x1 is unallocated) | = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information = note: inside `tests::it_works` at src/main.rs:16:35 note: inside closure at src/main.rs:14:5 --> src/main.rs:14:5 | 13 | #[test] | ------- in this procedural macro expansion 14 | / fn it_works() { 15 | | unsafe { 16 | | let _x: &'static u8 = core::mem::transmute(1usize); 17 | | } 18 | | } | |_____^ = note: this error originates in the attribute macro `test` (in Nightly builds, run with -Z macro-backtrace for more info) note: Some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace. error: aborting due to previous error error: test failed, to rerun pass '--bin scratch' ```
2022-02-22 15:39:07 +00:00 · 2022-02-22 15:39:07 +00:00 · c71006722e
commit c71006722e
parent d03b4a0c58 19ecd130b5
5 changed files with 76 additions and 2 deletions
--- a/src/bin/miri.rs
+++ b/src/bin/miri.rs
@ -29,6 +29,8 @@ use rustc_middle::{
 };
 use rustc_session::{config::ErrorOutputType, search_paths::PathKind, CtfeBacktrace};

+use miri::BacktraceStyle;
+
 struct MiriCompilerCalls {
    miri_config: miri::MiriConfig,
 }
@ -462,6 +464,14 @@ fn main() {
                    let measureme_out = arg.strip_prefix("-Zmiri-measureme=").unwrap();
                    miri_config.measureme_out = Some(measureme_out.to_string());
                }
+                arg if arg.starts_with("-Zmiri-backtrace=") => {
+                    miri_config.backtrace_style = match arg.strip_prefix("-Zmiri-backtrace=") {
+                        Some("0") => BacktraceStyle::Off,
+                        Some("1") => BacktraceStyle::Short,
+                        Some("full") => BacktraceStyle::Full,
+                        _ => panic!("-Zmiri-backtrace may only be 0, 1, or full"),
+                    };
+                }
                _ => {
                    // Forward to rustc.
                    rustc_args.push(arg);
--- a/src/diagnostics.rs
+++ b/src/diagnostics.rs
@ -157,6 +157,46 @@ pub fn report_error<'tcx, 'mir>(
        }
    };

+    let mut stacktrace = ecx.generate_stacktrace();
+    let has_local_frame = stacktrace.iter().any(|frame| frame.instance.def_id().is_local());
+    match ecx.machine.backtrace_style {
+        BacktraceStyle::Off => {
+            // Retain one frame so that we can print a span for the error itself
+            stacktrace.truncate(1);
+        }
+        BacktraceStyle::Short => {
+            // Only prune frames if there is at least one local frame. This check ensures that if
+            // we get a backtrace that never makes it to the user code because it has detected a
+            // bug in the Rust runtime, we don't prune away every frame.
+            if has_local_frame {
+                // This is part of the logic that `std` uses to select the relevant part of a
+                // backtrace. But here, we only look for __rust_begin_short_backtrace, not
+                // __rust_end_short_backtrace because the end symbol comes from a call to the default
+                // panic handler.
+                stacktrace = stacktrace
+                    .into_iter()
+                    .take_while(|frame| {
+                        let def_id = frame.instance.def_id();
+                        let path = ecx.tcx.tcx.def_path_str(def_id);
+                        !path.contains("__rust_begin_short_backtrace")
+                    })
+                    .collect::<Vec<_>>();
+
+                // After we prune frames from the bottom, there are a few left that are part of the
+                // Rust runtime. So we remove frames until we get to a local symbol, which should be
+                // main or a test.
+                // This len check ensures that we don't somehow remove every frame, as doing so breaks
+                // the primary error message.
+                while stacktrace.len() > 1
+                    && stacktrace.last().map_or(false, |e| !e.instance.def_id().is_local())
+                {
+                    stacktrace.pop();
+                }
+            }
+        }
+        BacktraceStyle::Full => {}
+    }
+
    e.print_backtrace();
    let msg = e.to_string();
    report_msg(
@ -165,9 +205,17 @@ pub fn report_error<'tcx, 'mir>(
        &if let Some(title) = title { format!("{}: {}", title, msg) } else { msg.clone() },
        msg,
        helps,
-        &ecx.generate_stacktrace(),
+        &stacktrace,
    );

+    // Include a note like `std` does for short backtraces, but since we are opt-out not opt-in, we
+    // do not include a note when backtraces are off.
+    if ecx.machine.backtrace_style == BacktraceStyle::Short && has_local_frame {
+        ecx.tcx.sess.diagnostic().note_without_error(
+            "some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace",
+        );
+    }
+
    // Debug-dump all locals.
    for (i, frame) in ecx.active_thread_stack().iter().enumerate() {
        trace!("-------------------");
--- a/src/eval.rs
+++ b/src/eval.rs
@ -57,6 +57,16 @@ pub enum IsolatedOp {
    Allow,
 }

+#[derive(Copy, Clone, PartialEq, Eq)]
+pub enum BacktraceStyle {
+    /// Prints a terser backtrace which ideally only contains relevant information.
+    Short,
+    /// Prints a backtrace with all possible information.
+    Full,
+    /// Prints only the frame that the error occurs in.
+    Off,
+}
+
 /// Configuration needed to spawn a Miri instance.
 #[derive(Clone)]
 pub struct MiriConfig {
@ -98,6 +108,7 @@ pub struct MiriConfig {
    pub measureme_out: Option<String>,
    /// Panic when unsupported functionality is encountered
    pub panic_on_unsupported: bool,
+    pub backtrace_style: BacktraceStyle,
 }

 impl Default for MiriConfig {
@ -121,6 +132,7 @@ impl Default for MiriConfig {
            cmpxchg_weak_failure_rate: 0.8,
            measureme_out: None,
            panic_on_unsupported: false,
+            backtrace_style: BacktraceStyle::Short,
        }
    }
 }
--- a/src/lib.rs
+++ b/src/lib.rs
@ -60,7 +60,7 @@ pub use crate::diagnostics::{
    NonHaltingDiagnostic, TerminationInfo,
 };
 pub use crate::eval::{
-    create_ecx, eval_entry, AlignmentCheck, IsolatedOp, MiriConfig, RejectOpWith,
+    create_ecx, eval_entry, AlignmentCheck, BacktraceStyle, IsolatedOp, MiriConfig, RejectOpWith,
 };
 pub use crate::helpers::EvalContextExt as HelpersEvalContextExt;
 pub use crate::machine::{
--- a/src/machine.rs
+++ b/src/machine.rs
@ -343,6 +343,9 @@ pub struct Evaluator<'mir, 'tcx> {
    /// functionality is encountered. If `false`, an error is propagated in the Miri application context
    /// instead (default behavior)
    pub(crate) panic_on_unsupported: bool,
+
+    /// Equivalent setting as RUST_BACKTRACE on encountering an error.
+    pub(crate) backtrace_style: BacktraceStyle,
 }

 impl<'mir, 'tcx> Evaluator<'mir, 'tcx> {
@ -374,6 +377,7 @@ impl<'mir, 'tcx> Evaluator<'mir, 'tcx> {
            string_cache: Default::default(),
            exported_symbols_cache: FxHashMap::default(),
            panic_on_unsupported: config.panic_on_unsupported,
+            backtrace_style: config.backtrace_style,
        }
    }