fix(ext/ffi): disallow empty ffi structs (#17487)

This patch makes `NativeType` to `libffi::middle::Type` conversion
failliable and w.t disallows struct with empty fields. libffi does not
handle "empty" struct because they don't exist in C (or Rust).

Fixes #17481

ext/ffi/call.rs

@@ -278,7 +278,7 @@ where
     permissions.check(None)?;
   };
 
-  let symbol = PtrSymbol::new(pointer, &def);
+  let symbol = PtrSymbol::new(pointer, &def)?;
   let call_args = ffi_parse_args(scope, parameters, &def.parameters)?;
   let def_result = def.result.clone();
 
@@ -379,7 +379,7 @@ where
     permissions.check(None)?;
   };
 
-  let symbol = PtrSymbol::new(pointer, &def);
+  let symbol = PtrSymbol::new(pointer, &def)?;
   let call_args = ffi_parse_args(scope, parameters, &def.parameters)?;
 
   let out_buffer = out_buffer

ext/ffi/callback.rs

@@ -40,18 +40,19 @@ pub struct PtrSymbol {
 }
 
 impl PtrSymbol {
-  pub fn new(fn_ptr: usize, def: &ForeignFunction) -> Self {
+  pub fn new(fn_ptr: usize, def: &ForeignFunction) -> Result<Self, AnyError> {
     let ptr = libffi::middle::CodePtr::from_ptr(fn_ptr as _);
     let cif = libffi::middle::Cif::new(
       def
         .parameters
         .clone()
         .into_iter()
-        .map(libffi::middle::Type::from),
-      def.result.clone().into(),
+        .map(libffi::middle::Type::try_from)
+        .collect::<Result<Vec<_>, _>>()?,
+      def.result.clone().try_into()?,
     );
 
-    Self { cif, ptr }
+    Ok(Self { cif, ptr })
   }
 }
 
@@ -578,8 +579,12 @@ where
     waker: None,
   }));
   let cif = Cif::new(
-    args.parameters.into_iter().map(libffi::middle::Type::from),
-    libffi::middle::Type::from(args.result),
+    args
+      .parameters
+      .into_iter()
+      .map(libffi::middle::Type::try_from)
+      .collect::<Result<Vec<_>, _>>()?,
+    libffi::middle::Type::try_from(args.result)?,
   );
 
   // SAFETY: CallbackInfo is leaked, is not null and stays valid as long as the callback exists.

ext/ffi/dlfcn.rs

@@ -166,8 +166,9 @@ where
             .parameters
             .clone()
             .into_iter()
-            .map(libffi::middle::Type::from),
-          foreign_fn.result.clone().into(),
+            .map(libffi::middle::Type::try_from)
+            .collect::<Result<Vec<_>, _>>()?,
+          foreign_fn.result.clone().try_into()?,
         );
 
         let func_key = v8::String::new(scope, &symbol_key).unwrap();

ext/ffi/symbol.rs

@@ -1,5 +1,8 @@
 // Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
 
+use deno_core::error::type_error;
+use deno_core::error::AnyError;
+
 /// Defines the accepted types that can be used as
 /// parameters and return values in FFI.
 #[derive(Clone, Debug, serde::Deserialize, Eq, PartialEq)]
@@ -25,9 +28,11 @@ pub enum NativeType {
   Struct(Box<[NativeType]>),
 }
 
-impl From<NativeType> for libffi::middle::Type {
-  fn from(native_type: NativeType) -> Self {
-    match native_type {
+impl TryFrom<NativeType> for libffi::middle::Type {
+  type Error = AnyError;
+
+  fn try_from(native_type: NativeType) -> Result<Self, Self::Error> {
+    Ok(match native_type {
       NativeType::Void => libffi::middle::Type::void(),
       NativeType::U8 | NativeType::Bool => libffi::middle::Type::u8(),
       NativeType::I8 => libffi::middle::Type::i8(),
@@ -44,10 +49,18 @@ impl From<NativeType> for libffi::middle::Type {
       NativeType::Pointer | NativeType::Buffer | NativeType::Function => {
         libffi::middle::Type::pointer()
       }
-      NativeType::Struct(fields) => libffi::middle::Type::structure(
-        fields.iter().map(|field| field.clone().into()),
-      ),
+      NativeType::Struct(fields) => {
+        libffi::middle::Type::structure(match fields.len() > 0 {
+          true => fields
+            .iter()
+            .map(|field| field.clone().try_into())
+            .collect::<Result<Vec<_>, _>>()?,
+          false => {
+            return Err(type_error("Struct must have at least one field"))
           }
+        })
+      }
+    })
   }
 }
 

test_ffi/tests/test.js

@@ -37,6 +37,40 @@ assertThrows(
   "Failed to register symbol non_existent_symbol",
 );
 
+assertThrows(() => {
+  Deno.dlopen(libPath, {
+    print_something: {
+      parameters: [],
+      result: { struct: [] }
+    },
+  }),
+  TypeError,
+  "Struct must have at least one field"
+});
+
+assertThrows(() => {
+  Deno.dlopen(libPath, {
+    print_something: {
+      parameters: [ { struct: [] } ],
+      result: "void",
+    },
+  }),
+  TypeError,
+  "Struct must have at least one field"
+});
+
+const Empty = { struct: [] }
+assertThrows(() => {
+  Deno.dlopen(libPath, {
+    print_something: {
+      parameters: [ { struct: [Empty] } ],
+      result: "void",
+    },
+  }),
+  TypeError,
+  "Struct must have at least one field"
+});
+
 const Point = ["f64", "f64"];
 const Size = ["f64", "f64"];
 const Rect = ["f64", "f64", "f64", "f64"];