Get rid of CBox

nix-rust/src/c.rs

@@ -1,20 +1,21 @@
 use super::{
     error,
-    foreign::{self, CBox},
+    foreign::{self},
     store::path,
     store::StorePath,
     util,
 };
 
 #[no_mangle]
-pub extern "C" fn unpack_tarfile(
+pub unsafe extern "C" fn unpack_tarfile(
     source: foreign::Source,
     dest_dir: &str,
-) -> CBox<Result<(), error::CppException>> {
-    CBox::new(
+    out: *mut Result<(), error::CppException>,
+) {
+    out.write(
         util::tarfile::unpack_tarfile(source, std::path::Path::new(dest_dir))
             .map_err(|err| err.into()),
-    )
+    );
 }
 
 #[no_mangle]

nix-rust/src/foreign.rs

@@ -12,22 +12,3 @@ impl std::io::Read for Source {
         Ok(n)
     }
 }
-
-pub struct CBox<T> {
-    pub ptr: *mut libc::c_void,
-    phantom: std::marker::PhantomData<T>,
-}
-
-impl<T> CBox<T> {
-    pub fn new(t: T) -> Self {
-        unsafe {
-            let size = std::mem::size_of::<T>();
-            let ptr = libc::malloc(size);
-            *(ptr as *mut T) = t; // FIXME: probably UB
-            Self {
-                ptr,
-                phantom: std::marker::PhantomData,
-            }
-        }
-    }
-}