make cargo-miri show_error a bit nicer to use

cargo-miri/src/main.rs

@@ -1,10 +1,12 @@
 #![feature(let_else)]
 #![allow(clippy::useless_format, clippy::derive_partial_eq_without_eq, rustc::internal)]
 
+#[macro_use]
+mod util;
+
 mod arg;
 mod phases;
 mod setup;
-mod util;
 mod version;
 
 use std::{env, iter};
@@ -73,9 +75,9 @@ fn main() {
     }
 
     let Some(first) = args.next() else {
-        show_error(format!(
+        show_error!(
             "`cargo-miri` called without first argument; please only invoke this binary through `cargo miri`"
-        ))
+        )
     };
     match first.as_str() {
         "miri" => phase_cargo_miri(args),

cargo-miri/src/phases.rs

@@ -77,15 +77,15 @@ pub fn phase_cargo_miri(mut args: impl Iterator<Item = String>) {
     // We cannot know which of those flags take arguments and which do not,
     // so we cannot detect subcommands later.
     let Some(subcommand) = args.next() else {
-        show_error(format!("`cargo miri` needs to be called with a subcommand (`run`, `test`)"));
+        show_error!("`cargo miri` needs to be called with a subcommand (`run`, `test`)");
     };
     let subcommand = match &*subcommand {
         "setup" => MiriCommand::Setup,
         "test" | "t" | "run" | "r" | "nextest" => MiriCommand::Forward(subcommand),
         _ =>
-            show_error(format!(
+            show_error!(
                 "`cargo miri` supports the following subcommands: `run`, `test`, `nextest`, and `setup`."
-            )),
+            ),
     };
     let verbose = num_arg_flag("-v");
 
@@ -123,7 +123,7 @@ pub fn phase_cargo_miri(mut args: impl Iterator<Item = String>) {
         match arg {
             Ok(value) => {
                 if target_dir.is_some() {
-                    show_error(format!("`--target-dir` is provided more than once"));
+                    show_error!("`--target-dir` is provided more than once");
                 }
                 target_dir = Some(value.into());
             }
@@ -456,16 +456,13 @@ pub fn phase_runner(mut binary_args: impl Iterator<Item = String>, phase: Runner
 
     let binary = binary_args.next().unwrap();
     let file = File::open(&binary)
-        .unwrap_or_else(|_| show_error(format!(
+        .unwrap_or_else(|_| show_error!(
             "file {:?} not found or `cargo-miri` invoked incorrectly; please only invoke this binary through `cargo miri`", binary
-        )));
+        ));
     let file = BufReader::new(file);
 
     let info = serde_json::from_reader(file).unwrap_or_else(|_| {
-        show_error(format!(
+        show_error!("file {:?} contains outdated or invalid JSON; try `cargo clean`", binary)
-            "file {:?} contains outdated or invalid JSON; try `cargo clean`",
-            binary
-        ))
     });
     let info = match info {
         CrateRunInfo::RunWith(info) => info,
@@ -562,7 +559,7 @@ pub fn phase_rustdoc(mut args: impl Iterator<Item = String>) {
             // An existing --runtool flag indicates cargo is running in cross-target mode, which we don't support.
             // Note that this is only passed when cargo is run with the unstable -Zdoctest-xcompile flag;
             // otherwise, we won't be called as rustdoc at all.
-            show_error(format!("cross-interpreting doctests is not currently supported by Miri."));
+            show_error!("cross-interpreting doctests is not currently supported by Miri.");
         } else {
             cmd.arg(arg);
         }

cargo-miri/src/setup.rs

@@ -73,7 +73,7 @@ pub fn setup(subcommand: &MiriCommand, host: &str, target: &str) {
     if xargo_version().map_or(true, |v| v < XARGO_MIN_VERSION) {
         if std::env::var_os("XARGO_CHECK").is_some() {
             // The user manually gave us a xargo binary; don't do anything automatically.
-            show_error(format!("xargo is too old; please upgrade to the latest version"))
+            show_error!("xargo is too old; please upgrade to the latest version")
         }
         let mut cmd = cargo();
         cmd.args(&["install", "xargo"]);
@@ -97,10 +97,10 @@ pub fn setup(subcommand: &MiriCommand, host: &str, target: &str) {
                 .output()
                 .expect("failed to determine sysroot");
             if !output.status.success() {
-                show_error(format!(
+                show_error!(
                     "Failed to determine sysroot; Miri said:\n{}",
                     String::from_utf8_lossy(&output.stderr).trim_end()
-                ));
+                );
             }
             let sysroot = std::str::from_utf8(&output.stdout).unwrap();
             let sysroot = Path::new(sysroot.trim_end_matches('\n'));
@@ -121,14 +121,14 @@ pub fn setup(subcommand: &MiriCommand, host: &str, target: &str) {
         }
     };
     if !rust_src.exists() {
-        show_error(format!("given Rust source directory `{}` does not exist.", rust_src.display()));
+        show_error!("given Rust source directory `{}` does not exist.", rust_src.display());
     }
     if rust_src.file_name().and_then(OsStr::to_str) != Some("library") {
-        show_error(format!(
+        show_error!(
             "given Rust source directory `{}` does not seem to be the `library` subdirectory of \
              a Rust source checkout.",
             rust_src.display()
-        ));
+        );
     }
 
     // Next, we need our own libstd. Prepare a xargo project for that purpose.
@@ -226,11 +226,9 @@ pub fn setup(subcommand: &MiriCommand, host: &str, target: &str) {
     // Finally run it!
     if command.status().expect("failed to run xargo").success().not() {
         if only_setup {
-            show_error(format!("failed to run xargo, see error details above"))
+            show_error!("failed to run xargo, see error details above")
         } else {
-            show_error(format!(
+            show_error!("failed to run xargo; run `cargo miri setup` to see the error details")
-                "failed to run xargo; run `cargo miri setup` to see the error details"
-            ))
         }
     }
 

cargo-miri/src/util.rs

@@ -14,6 +14,15 @@
 
 pub use crate::arg::*;
 
+pub fn show_error(msg: &str) -> ! {
+    eprintln!("fatal error: {msg}");
+    std::process::exit(1)
+}
+
+macro_rules! show_error {
+    ($($tt:tt)*) => { show_error(&format!($($tt)*)) };
+}
+
 /// The information to run a crate with the given environment.
 #[derive(Clone, Serialize, Deserialize)]
 pub struct CrateRunEnv {
@@ -55,10 +64,10 @@ pub enum CrateRunInfo {
 impl CrateRunInfo {
     pub fn store(&self, filename: &Path) {
         let file = File::create(filename)
-            .unwrap_or_else(|_| show_error(format!("cannot create `{}`", filename.display())));
+            .unwrap_or_else(|_| show_error!("cannot create `{}`", filename.display()));
         let file = BufWriter::new(file);
         serde_json::ser::to_writer(file, self)
-            .unwrap_or_else(|_| show_error(format!("cannot write to `{}`", filename.display())));
+            .unwrap_or_else(|_| show_error!("cannot write to `{}`", filename.display()));
     }
 }
 
@@ -70,11 +79,6 @@ pub enum MiriCommand {
     Forward(String),
 }
 
-pub fn show_error(msg: String) -> ! {
-    eprintln!("fatal error: {}", msg);
-    std::process::exit(1)
-}
-
 /// Escapes `s` in a way that is suitable for using it as a string literal in TOML syntax.
 pub fn escape_for_toml(s: &str) -> String {
     // We want to surround this string in quotes `"`. So we first escape all quotes,
@@ -187,15 +191,15 @@ pub fn ask_to_run(mut cmd: Command, ask: bool, text: &str) {
         match buf.trim().to_lowercase().as_ref() {
             // Proceed.
             "" | "y" | "yes" => {}
-            "n" | "no" => show_error(format!("aborting as per your request")),
+            "n" | "no" => show_error!("aborting as per your request"),
-            a => show_error(format!("invalid answer `{}`", a)),
+            a => show_error!("invalid answer `{}`", a),
         };
     } else {
         eprintln!("Running `{:?}` to {}.", cmd, text);
     }
 
     if cmd.status().unwrap_or_else(|_| panic!("failed to execute {:?}", cmd)).success().not() {
-        show_error(format!("failed to {}", text));
+        show_error!("failed to {}", text);
     }
 }