simplify the logic by using owned results

cpetig · Aug 1, 2024 · a2d05a7 · a2d05a7
1 parent df019cf
commit a2d05a7
Show file tree

Hide file tree

Showing 4 changed files with 18 additions and 109 deletions.
diff --git a/crates/cpp/DESIGN.md b/crates/cpp/DESIGN.md
@@ -72,11 +72,9 @@ For now for functions the following convention is used in both directions:
     - (unchanged) If there are too many (>1) flat results, a local
       uninitialized ret_area is passed via the last argument
 
-    - (change) Returned strings and lists become views, valid until a
-      cabi_post on the ret_area ptr which was passed to the first call.
-      This is mostly a concession to functional safety, avoiding all
-      allocations in the hot path. Caller provided buffers or custom realloc
-      would solve this in a different way.
+    - (unchanged) Returned objects are owned.
+      For functional safety, i.e. avoiding all
+      allocations in the hot path, the hope is with #385.
 
  - The imported resource ABI is used also for exporting
    with one modification:

diff --git a/crates/cpp/tests/meshless_strings/component_a/the_world.cpp b/crates/cpp/tests/meshless_strings/component_a/the_world.cpp
@@ -31,15 +31,9 @@ fooX3AfooX2FstringsX00a(uint8_t *, size_t);
 extern "C" __attribute__((import_module("foo:foo/strings")))
 __attribute__((import_name("b"))) void
 fooX3AfooX2FstringsX00b(uint8_t *);
-extern "C" __attribute__((import_module("cabi_post_foo:foo/strings")))
-__attribute__((import_name("b"))) void
-cabi_post_fooX3AfooX2FstringsX00b(uint8_t *);
 extern "C" __attribute__((import_module("foo:foo/strings")))
 __attribute__((import_name("c"))) void
 fooX3AfooX2FstringsX00c(uint8_t *, size_t, uint8_t *, size_t, uint8_t *);
-extern "C" __attribute__((import_module("cabi_post_foo:foo/strings")))
-__attribute__((import_name("c"))) void
-cabi_post_fooX3AfooX2FstringsX00c(uint8_t *);
 void comp_a::foo::foo::strings::A(std::string_view x) {
   auto const &vec0 = x;
   auto ptr0 = (uint8_t *)(vec0.data());
@@ -53,10 +47,7 @@ wit::string comp_a::foo::foo::strings::B() {
   fooX3AfooX2FstringsX00b(ptr0);
   auto len1 = *((size_t *)(ptr0 + sizeof(void *)));
 
-  auto string1 = wit::string::from_view(
-      std::string_view((char const *)(*((uint8_t **)(ptr0 + 0))), len1));
-
-  cabi_post_fooX3AfooX2FstringsX00b(ptr0);
+  auto string1 = wit::string((char const *)(*((uint8_t **)(ptr0 + 0))), len1);
   return string1;
 }
 wit::string comp_a::foo::foo::strings::C(std::string_view a,
@@ -73,10 +64,7 @@ wit::string comp_a::foo::foo::strings::C(std::string_view a,
   fooX3AfooX2FstringsX00c(ptr0, len0, ptr1, len1, ptr2);
   auto len3 = *((size_t *)(ptr2 + sizeof(void *)));
 
-  auto string3 = wit::string::from_view(
-      std::string_view((char const *)(*((uint8_t **)(ptr2 + 0))), len3));
-
-  cabi_post_fooX3AfooX2FstringsX00c(ptr2);
+  auto string3 = wit::string((char const *)(*((uint8_t **)(ptr2 + 0))), len3);
   return string3;
 }
 extern "C" __attribute__((__export_name__("foo:foo/strings#a"))) void
@@ -99,14 +87,6 @@ a_fooX3AfooX2FstringsX00b(uint8_t *arg0) {
   *((size_t *)(arg0 + sizeof(void *))) = len1;
   *((uint8_t **)(arg0 + 0)) = ptr1;
 }
-extern "C"
-    __attribute__((__weak__,
-                   __export_name__("cabi_post_fooX3AfooX2FstringsX00b"))) void
-    a_cabi_post_fooX3AfooX2FstringsX00b(uint8_t *retptr) {
-  if ((*((size_t *)(retptr + sizeof(void *)))) > 0) {
-    wit::string::drop_raw((void *)(*((uint8_t **)(retptr + 0))));
-  }
-}
 extern "C" __attribute__((__export_name__("foo:foo/strings#c"))) void
 a_fooX3AfooX2FstringsX00c(uint8_t *arg0, size_t arg1, uint8_t *arg2, size_t arg3,
                         uint8_t *arg4) {
@@ -130,13 +110,5 @@ a_fooX3AfooX2FstringsX00c(uint8_t *arg0, size_t arg1, uint8_t *arg2, size_t arg3
   *((size_t *)(arg4 + sizeof(void *))) = len3;
   *((uint8_t **)(arg4 + 0)) = ptr3;
 }
-extern "C"
-    __attribute__((__weak__,
-                   __export_name__("cabi_post_fooX3AfooX2FstringsX00c"))) void
-    a_cabi_post_fooX3AfooX2FstringsX00c(uint8_t *retptr) {
-  if ((*((size_t *)(retptr + sizeof(void *)))) > 0) {
-    wit::string::drop_raw((void *)(*((uint8_t **)(retptr + 0))));
-  }
-}
 
 // Component Adapters
diff --git a/crates/cpp/tests/meshless_strings/component_b/the_world.cpp b/crates/cpp/tests/meshless_strings/component_b/the_world.cpp
@@ -31,15 +31,9 @@ a_fooX3AfooX2FstringsX00a(uint8_t *, size_t);
 extern "C" __attribute__((import_module("foo:foo/strings")))
 __attribute__((import_name("b"))) void
 a_fooX3AfooX2FstringsX00b(uint8_t *);
-extern "C" __attribute__((import_module("cabi_post_foo:foo/strings")))
-__attribute__((import_name("b"))) void
-a_cabi_post_fooX3AfooX2FstringsX00b(uint8_t *);
 extern "C" __attribute__((import_module("foo:foo/strings")))
 __attribute__((import_name("c"))) void
 a_fooX3AfooX2FstringsX00c(uint8_t *, size_t, uint8_t *, size_t, uint8_t *);
-extern "C" __attribute__((import_module("cabi_post_foo:foo/strings")))
-__attribute__((import_name("c"))) void
-a_cabi_post_fooX3AfooX2FstringsX00c(uint8_t *);
 void foo::foo::strings::A(std::string_view x) {
   auto const &vec0 = x;
   auto ptr0 = (uint8_t *)(vec0.data());
@@ -53,10 +47,7 @@ wit::string foo::foo::strings::B() {
   a_fooX3AfooX2FstringsX00b(ptr0);
   auto len1 = *((size_t *)(ptr0 + sizeof(void *)));
 
-  auto string1 = wit::string::from_view(
-      std::string_view((char const *)(*((uint8_t **)(ptr0 + 0))), len1));
-
-  a_cabi_post_fooX3AfooX2FstringsX00b(ptr0);
+  auto string1 = wit::string((char const *)(*((uint8_t **)(ptr0 + 0))), len1);
   return string1;
 }
 wit::string foo::foo::strings::C(std::string_view a, std::string_view b) {
@@ -72,10 +63,7 @@ wit::string foo::foo::strings::C(std::string_view a, std::string_view b) {
   a_fooX3AfooX2FstringsX00c(ptr0, len0, ptr1, len1, ptr2);
   auto len3 = *((size_t *)(ptr2 + sizeof(void *)));
 
-  auto string3 = wit::string::from_view(
-      std::string_view((char const *)(*((uint8_t **)(ptr2 + 0))), len3));
-
-  a_cabi_post_fooX3AfooX2FstringsX00c(ptr2);
+  auto string3 = wit::string((char const *)(*((uint8_t **)(ptr2 + 0))), len3);
   return string3;
 }
 extern "C" __attribute__((__export_name__("foo:foo/strings#a"))) void
@@ -98,14 +86,6 @@ fooX3AfooX2FstringsX00b(uint8_t *arg0) {
   *((size_t *)(arg0 + sizeof(void *))) = len1;
   *((uint8_t **)(arg0 + 0)) = ptr1;
 }
-extern "C"
-    __attribute__((__weak__,
-                   __export_name__("cabi_post_fooX3AfooX2FstringsX00b"))) void
-    cabi_post_fooX3AfooX2FstringsX00b(uint8_t *retptr) {
-  if ((*((size_t *)(retptr + sizeof(void *)))) > 0) {
-    wit::string::drop_raw((void *)(*((uint8_t **)(retptr + 0))));
-  }
-}
 extern "C" __attribute__((__export_name__("foo:foo/strings#c"))) void
 fooX3AfooX2FstringsX00c(uint8_t *arg0, size_t arg1, uint8_t *arg2, size_t arg3,
                         uint8_t *arg4) {
@@ -129,13 +109,5 @@ fooX3AfooX2FstringsX00c(uint8_t *arg0, size_t arg1, uint8_t *arg2, size_t arg3,
   *((size_t *)(arg4 + sizeof(void *))) = len3;
   *((uint8_t **)(arg4 + 0)) = ptr3;
 }
-extern "C"
-    __attribute__((__weak__,
-                   __export_name__("cabi_post_fooX3AfooX2FstringsX00c"))) void
-    cabi_post_fooX3AfooX2FstringsX00c(uint8_t *retptr) {
-  if ((*((size_t *)(retptr + sizeof(void *)))) > 0) {
-    wit::string::drop_raw((void *)(*((uint8_t **)(retptr + 0))));
-  }
-}
 
 // Component Adapters
diff --git a/crates/cpp/tests/meshless_strings/rust_comp_a/src/the_world.rs b/crates/cpp/tests/meshless_strings/rust_comp_a/src/the_world.rs
@@ -49,16 +49,8 @@ pub mod foo {
                     let l1 = *ptr0.add(0).cast::<*mut u8>();
                     let l2 = *ptr0.add(core::mem::size_of::<*const u8>()).cast::<usize>();
                     let len3 = l2;
-                    let string3 = String::from(
-                        std::str::from_utf8(std::slice::from_raw_parts(l1, len3)).unwrap(),
-                    );
-
-                    #[link(wasm_import_module = "cabi_post_foo:foo/strings")]
-                    extern "C" {
-                        #[cfg_attr(target_arch = "wasm32", link_name = "b")]
-                        fn cabi_post_fooX3AfooX2FstringsX00b(_: *mut u8);
-                    }
-                    cabi_post_fooX3AfooX2FstringsX00b(ptr0);
+                    let bytes3 = _rt::Vec::from_raw_parts(l1.cast(), len3, len3);
+                    let string3 = _rt::string_lift(bytes3);
                     string3
                 }
             }
@@ -96,16 +88,8 @@ pub mod foo {
                     let l3 = *ptr2.add(0).cast::<*mut u8>();
                     let l4 = *ptr2.add(core::mem::size_of::<*const u8>()).cast::<usize>();
                     let len5 = l4;
-                    let string5 = String::from(
-                        std::str::from_utf8(std::slice::from_raw_parts(l3, len5)).unwrap(),
-                    );
-
-                    #[link(wasm_import_module = "cabi_post_foo:foo/strings")]
-                    extern "C" {
-                        #[cfg_attr(target_arch = "wasm32", link_name = "c")]
-                        fn cabi_post_fooX3AfooX2FstringsX00c(_: *mut u8);
-                    }
-                    cabi_post_fooX3AfooX2FstringsX00c(ptr2);
+                    let bytes5 = _rt::Vec::from_raw_parts(l3.cast(), len5, len5);
+                    let string5 = _rt::string_lift(bytes5);
                     string5
                 }
             }
@@ -152,13 +136,6 @@ pub mod exports {
                 }
                 #[doc(hidden)]
                 #[allow(non_snake_case)]
-                pub unsafe fn __post_return_b<T: Guest>(arg0: *mut u8) {
-                    let l0 = *arg0.add(0).cast::<*mut u8>();
-                    let l1 = *arg0.add(core::mem::size_of::<*const u8>()).cast::<usize>();
-                    _rt::cabi_dealloc(l0, l1, 1);
-                }
-                #[doc(hidden)]
-                #[allow(non_snake_case)]
                 pub unsafe fn _export_c_cabi<T: Guest>(
                     arg0: *mut u8,
                     arg1: usize,
@@ -184,13 +161,6 @@ pub mod exports {
                     *arg4.add(core::mem::size_of::<*const u8>()).cast::<usize>() = len3;
                     *arg4.add(0).cast::<*mut u8>() = ptr3.cast_mut();
                 }
-                #[doc(hidden)]
-                #[allow(non_snake_case)]
-                pub unsafe fn __post_return_c<T: Guest>(arg0: *mut u8) {
-                    let l0 = *arg0.add(0).cast::<*mut u8>();
-                    let l1 = *arg0.add(core::mem::size_of::<*const u8>()).cast::<usize>();
-                    _rt::cabi_dealloc(l0, l1, 1);
-                }
                 pub trait Guest {
                     fn a(x: _rt::String) -> ();
                     fn b() -> _rt::String;
@@ -211,21 +181,11 @@ pub mod exports {
       unsafe extern "C" fn a_fooX3AfooX2FstringsX00b(ptr: *mut u8) {
         $($path_to_types)*::_export_b_cabi::<$ty>(ptr)
       }
-      #[cfg_attr(target_arch = "wasm32", export_name = "cabi_post_foo:foo/strings#b")]
-      #[cfg_attr(not(target_arch = "wasm32"), no_mangle)]
-      unsafe extern "C" fn a_cabi_post_fooX3AfooX2FstringsX00b(arg0: *mut u8,) {
-        $($path_to_types)*::__post_return_b::<$ty>(arg0)
-      }
       #[cfg_attr(target_arch = "wasm32", export_name = "foo:foo/strings#c")]
       #[cfg_attr(not(target_arch = "wasm32"), no_mangle)]
       unsafe extern "C" fn a_fooX3AfooX2FstringsX00c(arg0: *mut u8,arg1: usize,arg2: *mut u8,arg3: usize, arg4: *mut u8) {
         $($path_to_types)*::_export_c_cabi::<$ty>(arg0, arg1, arg2, arg3, arg4)
       }
-      #[cfg_attr(target_arch = "wasm32", export_name = "cabi_post_foo:foo/strings#c")]
-      #[cfg_attr(not(target_arch = "wasm32"), no_mangle)]
-      unsafe extern "C" fn a_cabi_post_fooX3AfooX2FstringsX00c(arg0: *mut u8,) {
-        $($path_to_types)*::__post_return_c::<$ty>(arg0)
-      }
     };);
   }
                 #[doc(hidden)]
@@ -237,6 +197,13 @@ pub mod exports {
 mod _rt {
     pub use alloc_crate::string::String;
     pub use alloc_crate::vec::Vec;
+    pub unsafe fn string_lift(bytes: Vec<u8>) -> String {
+        if cfg!(debug_assertions) {
+            String::from_utf8(bytes).unwrap()
+        } else {
+            String::from_utf8_unchecked(bytes)
+        }
+    }
 
     #[cfg(target_arch = "wasm32")]
     pub fn run_ctors_once() {