PR edits requested by @RalfJung: main changes are removing the use of hir types, some refactoring/renaming of functions, and edits to the related test file hierarchy

Author: Ellen Arteca

README.md

@@ -285,6 +285,12 @@ environment variable. We first document the most relevant and most commonly used
   `TERM` environment variable is excluded by default to [speed up the test
   harness](https://github.com/rust-lang/miri/issues/1702). This has no effect unless
   `-Zmiri-disable-isolation` is also set.
+* `-Zmiri-extern-so-file=<path to a shared object file>` is an experimental flag for providing support
+  for FFI calls.
+  **WARNING**: If an invalid/incorrect SO file is specified, this can cause undefined behaviour in Miri itself!
+  This is [work in progress](https://github.com/rust-lang/miri/pull/2363); 
+  current support is for functions with integer arguments/returns.
+  Follow [the discussion on supporting other types](https://github.com/rust-lang/miri/issues/2365). 
 * `-Zmiri-env-forward=<var>` forwards the `var` environment variable to the interpreted program. Can
   be used multiple times to forward several variables. This takes precedence over
   `-Zmiri-env-exclude`: if a variable is both forwarded and exluced, it *will* get forwarded. This

miri

@@ -156,13 +156,6 @@ test|bless)
     # First build and get a sysroot.
     $CARGO build $CARGO_EXTRA_FLAGS --manifest-path "$MIRIDIR"/Cargo.toml
     find_sysroot
-    # if we're on linux
-    if [[ $OSTYPE == 'linux'* ]]; then
-        # rebuild the C test shared object file if it's not there
-        if [ ! -f "tests/external_C/libtestlib.so" ]; then
-            $CC -shared -o tests/external_C/libtestlib.so tests/external_C/test.c
-        fi
-    fi
     if [ "$COMMAND" = "bless" ]; then
         export MIRI_BLESS="Gesundheit"
     fi

src/bin/miri.rs

@@ -487,18 +487,18 @@ fn main() {
                 "full" => BacktraceStyle::Full,
                 _ => panic!("-Zmiri-backtrace may only be 0, 1, or full"),
             };
-        } else if let Some(param) = arg.strip_prefix("-Zmiri-external_c_so_file=") {
+        } else if let Some(param) = arg.strip_prefix("-Zmiri-extern-so-file=") {
             let filename = param.to_string();
             if std::path::Path::new(&filename).exists() {
-                if let Some(other_filename) = miri_config.external_c_so_file {
+                if let Some(other_filename) = miri_config.external_so_file {
                     panic!(
-                        "-Zmiri-external_so_file external SO file is already set to {}",
+                        "-Zmiri-extern-so-file external SO file is already set to {}",
                         other_filename.display()
                     );
                 }
-                miri_config.external_c_so_file = Some(filename.into());
+                miri_config.external_so_file = Some(filename.into());
             } else {
-                panic!("-Zmiri-external_c_so_file path {} does not exist", filename);
+                panic!("-Zmiri-extern-so-file path {} does not exist", filename);
             }
         } else {
             // Forward to rustc.

src/c_ffi_support.rs

@@ -127,9 +127,9 @@ pub struct MiriConfig {
     pub report_progress: Option<u32>,
     /// Whether Stacked Borrows retagging should recurse into fields of datatypes.
     pub retag_fields: bool,
-    /// The location of a shared object file to load when calling external C functions
+    /// The location of a shared object file to load when calling external functions
     /// TODO! consider allowing users to specify paths to multiple SO files, or to a directory
-    pub external_c_so_file: Option<PathBuf>,
+    pub external_so_file: Option<PathBuf>,
 }
 
 impl Default for MiriConfig {
@@ -161,7 +161,7 @@ impl Default for MiriConfig {
             preemption_rate: 0.01, // 1%
             report_progress: None,
             retag_fields: false,
-            external_c_so_file: None,
+            external_so_file: None,
         }
     }
 }

src/eval.rs

@@ -37,7 +37,6 @@ extern crate rustc_session;
 extern crate rustc_span;
 extern crate rustc_target;
 
-mod c_ffi_support;
 mod concurrency;
 mod diagnostics;
 mod eval;
@@ -70,8 +69,6 @@ pub use crate::shims::time::EvalContextExt as _;
 pub use crate::shims::tls::{EvalContextExt as _, TlsData};
 pub use crate::shims::EvalContextExt as _;
 
-pub use crate::c_ffi_support::EvalContextExt as CFFIEvalContextExt;
-
 pub use crate::concurrency::data_race::{
     AtomicFenceOrd, AtomicReadOrd, AtomicRwOrd, AtomicWriteOrd,
     EvalContextExt as DataRaceEvalContextExt,