Implement generic type for test_ftruncate

tests/pass-dep/shims/libc-fs.rs

@@ -17,9 +17,9 @@ fn main() {
     test_dup_stdout_stderr();
     test_canonicalize_too_long();
     test_rename();
-    test_ftruncate(libc::ftruncate);
+    test_ftruncate::<libc::off_t>(libc::ftruncate);
     #[cfg(target_os = "linux")]
-    test_ftruncate(libc::ftruncate64);
+    test_ftruncate::<libc::off64_t>(libc::ftruncate64);
     test_readlink();
     test_file_open_unix_allow_two_args();
     test_file_open_unix_needs_three_args();
@@ -162,7 +162,12 @@ fn test_rename() {
     remove_file(&path2).unwrap();
 }
 
-fn test_ftruncate(ftruncate: unsafe extern "C" fn(fd: libc::c_int, length: i64) -> libc::c_int) {
+fn test_ftruncate<T: Length>(
+    ftruncate: unsafe extern "C" fn(fd: libc::c_int, length: T) -> libc::c_int,
+) {
+    // libc::off_t is i32 in target i686-unknown-linux-gnu
+    // https://docs.rs/libc/latest/i686-unknown-linux-gnu/libc/type.off_t.html
+
     let bytes = b"hello";
     let path = prepare("miri_test_libc_fs_ftruncate.txt");
     let mut file = File::create(&path).unwrap();
@@ -174,7 +179,8 @@ fn test_ftruncate(ftruncate: unsafe extern "C" fn(fd: libc::c_int, length: i64)
     let fd = unsafe { libc::open(c_path.as_ptr(), libc::O_RDWR) };
 
     // Truncate to a bigger size
-    let mut res = unsafe { ftruncate(fd, 10) };
+    let length_10: i64 = 10;
+    let mut res = unsafe { ftruncate(fd, Length::convert(length_10)) };
     assert_eq!(res, 0);
     assert_eq!(file.metadata().unwrap().len(), 10);
 
@@ -184,7 +190,8 @@ fn test_ftruncate(ftruncate: unsafe extern "C" fn(fd: libc::c_int, length: i64)
     assert_eq!(file.metadata().unwrap().len(), 10);
 
     // Truncate to smaller size
-    res = unsafe { ftruncate(fd, 2) };
+    let length_2: i64 = 2;
+    res = unsafe { ftruncate(fd, Length::convert(length_2)) };
     assert_eq!(res, 0);
     assert_eq!(file.metadata().unwrap().len(), 2);
 
@@ -251,3 +258,20 @@ fn test_posix_mkstemp() {
         assert_eq!(e.kind(), std::io::ErrorKind::InvalidInput);
     }
 }
+
+// Trait implemented for test_ftruncate to convert i64 to the provided type
+trait Length: Sized {
+    fn convert(t: i64) -> Self;
+}
+
+impl Length for i32 {
+    fn convert(t: i64) -> i32 {
+        t as i32
+    }
+}
+
+impl Length for i64 {
+    fn convert(t: i64) -> i64 {
+        t
+    }
+}