Auto merge of #7535 - ehuss:better-windows-errors, r=alexcrichton

Show better error message for Windows abnormal termination.

This helps display better error messages when there is an abnormal termination on Windows.

If rustc crashes, there was a slight mistake in #6270, where the error code was actually negative, so the message was getting hidden behind the `--verbose` flag.  This changes it show that the abnormal error is always shown if rustc crashes in an unusual way.

This also changes `cargo test` to display a better message if the test crashes.  Previously:

```
running 1 test
error: test failed, to rerun pass '--bin crash'
```

New:

```
running 1 test
error: test failed, to rerun pass '--bin crash'

Caused by:
  process didn't exit successfully: `D:\Temp\crash\target\debug\deps\crash-b3c2389529da3d3e.exe` (exit code: 0xc0000374, STATUS_HEAP_CORRUPTION)
```

I didn't add any tests because testing on this on Windows seems a little precarious.  AFAIK, the exact error message depends on the processor (like x86 vs i686), and Windows version.  I was concerned about chasing down every little nuance, though I'm willing to try if it seems important.

Fixes rust-lang/rust#65692 (I think).

src/bin/cargo/commands/test.rs

@@ -1,6 +1,7 @@
-use cargo::ops::{self, CompileFilter, FilterRule, LibRule};
-
 use crate::command_prelude::*;
+use cargo::ops::{self, CompileFilter, FilterRule, LibRule};
+use cargo::util::errors;
+use failure::Fail;
 
 pub fn cli() -> App {
     subcommand("test")
@@ -164,12 +165,15 @@ pub fn exec(config: &mut Config, args: &ArgMatches<'_>) -> CliResult {
     let err = ops::run_tests(&ws, &ops, &test_args)?;
     match err {
         None => Ok(()),
-        Some(err) => Err(match err.exit.as_ref().and_then(|e| e.code()) {
-            Some(i) => CliError::new(
-                failure::format_err!("{}", err.hint(&ws, &ops.compile_opts)),
-                i,
-            ),
-            None => CliError::new(err.into(), 101),
-        }),
+        Some(err) => {
+            let context = failure::format_err!("{}", err.hint(&ws, &ops.compile_opts));
+            let e = match err.exit.as_ref().and_then(|e| e.code()) {
+                // Don't show "process didn't exit successfully" for simple errors.
+                Some(i) if errors::is_simple_exit_code(i) => CliError::new(context, i),
+                Some(i) => CliError::new(err.context(context).into(), i),
+                None => CliError::new(err.context(context).into(), 101),
+            };
+            Err(e)
+        }
     }
 }

src/cargo/core/compiler/mod.rs

@@ -45,7 +45,7 @@ use crate::core::manifest::TargetSourcePath;
 use crate::core::profiles::{Lto, PanicStrategy, Profile};
 use crate::core::Feature;
 use crate::core::{PackageId, Target};
-use crate::util::errors::{CargoResult, CargoResultExt, Internal, ProcessError};
+use crate::util::errors::{self, CargoResult, CargoResultExt, Internal, ProcessError};
 use crate::util::machine_message::Message;
 use crate::util::paths;
 use crate::util::{self, machine_message, ProcessBuilder};
@@ -271,7 +271,7 @@ fn rustc<'a, 'cfg>(
                 .as_ref()
                 .and_then(|perr| perr.exit.and_then(|e| e.code()))
             {
-                Some(n) if n < 128 => Internal::new(err).into(),
+                Some(n) if errors::is_simple_exit_code(n) => Internal::new(err).into(),
                 _ => err,
             }
         }

src/cargo/util/errors.rs

@@ -381,6 +381,17 @@ pub fn process_error(
     }
 }
 
+pub fn is_simple_exit_code(code: i32) -> bool {
+    // Typical unix exit codes are 0 to 127.
+    // Windows doesn't have anything "typical", and is a
+    // 32-bit number (which appears signed here, but is really
+    // unsigned). However, most of the interesting NTSTATUS
+    // codes are very large. This is just a rough
+    // approximation of which codes are "normal" and which
+    // ones are abnormal termination.
+    code >= 0 && code <= 127
+}
+
 pub fn internal<S: fmt::Display>(error: S) -> failure::Error {
     _internal(&error)
 }