Use cargo locate-project (rust-lang#904)

* use message-format plain, update error handling

Author: tedinski

src/cargo-kani/src/args_toml.rs

@@ -4,19 +4,28 @@
 use anyhow::{bail, Result};
 use std::collections::BTreeMap;
 use std::ffi::OsString;
+use std::path::PathBuf;
+use std::process::Command;
 use toml::value::Table;
 use toml::Value;
 
 /// Produces a set of arguments to pass to ourself (cargo-kani) from a Cargo.toml project file
 pub fn config_toml_to_args() -> Result<Vec<OsString>> {
-    // TODO: `cargo locate-project` maybe?
-    let file = std::fs::read_to_string("Cargo.toml");
-    if let Ok(file) = file {
-        toml_to_args(&file)
-    } else {
-        // Suppress the error if we can't find it, for now.
-        Ok(vec![])
+    let file = std::fs::read_to_string(cargo_locate_project()?)?;
+    toml_to_args(&file)
+}
+
+/// `locate-project` produces a response like: `/full/path/to/src/cargo-kani/Cargo.toml`
+fn cargo_locate_project() -> Result<PathBuf> {
+    let cmd =
+        Command::new("cargo").args(["locate-project", "--message-format", "plain"]).output()?;
+    if !cmd.status.success() {
+        let err = std::str::from_utf8(&cmd.stderr)?;
+        bail!("{}", err);
     }
+    let path = std::str::from_utf8(&cmd.stdout)?;
+    // A trim is essential: remove the trailing newline
+    Ok(path.trim().into())
 }
 
 /// Parse a config toml string and extract the cargo-kani arguments we should try injecting

src/cargo-kani/src/call_cbmc.rs

@@ -109,6 +109,10 @@ impl KaniSession {
             args.push("--nan-check".into());
             args.push("--pointer-overflow-check".into());
             args.push("--undefined-shift-check".into());
+            // With PR #647 we use Rust's `-C overflow-checks=on` instead of:
+            // --unsigned-overflow-check
+            // --signed-overflow-check
+            // So these options are deliberately skipped to avoid erroneously re-checking operations.
         }
         if self.args.checks.unwinding_on() {
             args.push("--unwinding-assertions".into());

src/cargo-kani/src/call_goto_cc.rs

@@ -25,12 +25,8 @@ impl KaniSession {
 
         // Special case hack for handling the "c-ffi" abs-type
         if self.args.use_abs && self.args.abs_type == AbstractionType::CFfi {
-            let mut vec = self.kani_c_stubs.clone();
-            vec.push("vec");
-            vec.push("vec.c");
-            let mut hashset = self.kani_c_stubs.clone();
-            hashset.push("hashset");
-            hashset.push("hashset.c");
+            let vec = self.kani_c_stubs.join("vec/vec.c");
+            let hashset = self.kani_c_stubs.join("hashset/hashset.c");
 
             args.push(vec.into_os_string());
             args.push(hashset.into_os_string());

src/cargo-kani/src/util.rs

@@ -8,9 +8,7 @@ use std::process::Command;
 
 /// Replace an extension with another one, in a new PathBuf. (See tests for examples)
 pub fn alter_extension(path: &Path, ext: &str) -> PathBuf {
-    let mut result = path.to_owned();
-    result.set_extension(ext);
-    result
+    path.with_extension(ext)
 }
 
 /// Add an extension to an existing file path (amazingly Rust doesn't support this well)