ctest: add foreign fn tests

ctest-next/src/ast/mod.rs

@@ -7,6 +7,8 @@ mod structure;
 mod type_alias;
 mod union;
 
+use std::fmt;
+
 pub use constant::Const;
 pub use field::Field;
 pub use function::Fn;
@@ -37,6 +39,16 @@ impl From<&str> for Abi {
     }
 }
 
+impl fmt::Display for Abi {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Abi::C => write!(f, "C"),
+            Abi::Rust => write!(f, "Rust"),
+            Abi::Other(s) => write!(f, "{s}"),
+        }
+    }
+}
+
 /// Things that can appear directly inside of a module or scope.
 ///
 /// This is not an exhaustive list and only contains variants directly useful
@@ -47,7 +59,7 @@ pub(crate) enum Item {
     /// Represents a constant defined in Rust.
     Const(Const),
     /// Represents a function defined in Rust.
-    Fn(Fn),
+    Fn(Box<Fn>),
     /// Represents a static variable defined in Rust.
     Static(Static),
     /// Represents a type alias defined in Rust.

ctest-next/src/ffi_items.rs

@@ -57,7 +57,6 @@ impl FfiItems {
     }
 
     /// Return a list of all foreign functions found mapped by their ABI.
-    #[cfg_attr(not(test), expect(unused))]
     pub(crate) fn foreign_functions(&self) -> &Vec<Fn> {
         &self.foreign_functions
     }

ctest-next/src/generator.rs

@@ -42,10 +42,11 @@ pub struct TestGenerator {
     pub(crate) skips: Vec<Skip>,
     verbose_skip: bool,
     pub(crate) volatile_items: Vec<VolatileItem>,
-    array_arg: Option<ArrayArg>,
+    pub(crate) array_arg: Option<ArrayArg>,
     skip_private: bool,
     pub(crate) skip_roundtrip: Option<SkipTest>,
     pub(crate) skip_signededness: Option<SkipTest>,
+    pub(crate) skip_fn_ptrcheck: Option<SkipTest>,
 }
 
 #[derive(Debug, Error)]
@@ -856,6 +857,30 @@ impl TestGenerator {
         self
     }
 
+    /// Configures whether tests for a function pointer's value are generated.
+    ///
+    /// The closure is given a Rust FFI function and returns whether
+    /// the test will be generated.
+    ///
+    /// By default generated tests will ensure that the function pointer in C
+    /// corresponds to the same function pointer in Rust. This can often
+    /// uncover subtle symbol naming issues where a header file is referenced
+    /// through the C identifier `foo` but the underlying symbol is mapped to
+    /// something like `__foo_compat`.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use ctest_next::TestGenerator;
+    ///
+    /// let mut cfg = TestGenerator::new();
+    /// cfg.skip_fn_ptrcheck(|name| name == "T1p");
+    /// ```
+    pub fn skip_fn_ptrcheck(&mut self, f: impl Fn(&str) -> bool + 'static) -> &mut Self {
+        self.skip_fn_ptrcheck = Some(Box::new(f));
+        self
+    }
+
     /// Generate the Rust and C testing files.
     ///
     /// Returns the path to the generated file.

ctest-next/src/lib.rs

@@ -37,7 +37,7 @@ type BoxStr = Box<str>;
 ///
 /// This is necessary because `ctest` does not parse the header file, so it
 /// does not know which items are volatile.
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 #[non_exhaustive]
 pub enum VolatileItemKind {
     /// A struct field.

ctest-next/src/template.rs

@@ -4,7 +4,7 @@ use quote::ToTokens;
 use syn::spanned::Spanned;
 
 use crate::ffi_items::FfiItems;
-use crate::translator::Translator;
+use crate::translator::{TranslationErrorKind, Translator};
 use crate::{
     BoxStr, Field, MapInput, Result, TestGenerator, TranslationError, VolatileItemKind, cdecl,
 };
@@ -53,6 +53,7 @@ pub(crate) struct TestTemplate {
     pub field_ptr_tests: Vec<TestFieldPtr>,
     pub field_size_offset_tests: Vec<TestFieldSizeOffset>,
     pub roundtrip_tests: Vec<TestRoundtrip>,
+    pub foreign_fn_tests: Vec<TestForeignFn>,
     pub signededness_tests: Vec<TestSignededness>,
     pub size_align_tests: Vec<TestSizeAlign>,
     pub const_cstr_tests: Vec<TestCStr>,
@@ -75,6 +76,7 @@ impl TestTemplate {
         template.populate_field_size_offset_tests(&helper)?;
         template.populate_field_ptr_tests(&helper)?;
         template.populate_roundtrip_tests(&helper)?;
+        template.populate_foreign_fn_tests(&helper)?;
 
         Ok(template)
     }
@@ -359,7 +361,7 @@ impl TestTemplate {
             )
             .map_err(|_| {
                 TranslationError::new(
-                    crate::translator::TranslationErrorKind::InvalidReturn,
+                    TranslationErrorKind::InvalidReturn,
                     &field.ty.to_token_stream().to_string(),
                     field.ty.span(),
                 )
@@ -380,6 +382,38 @@ impl TestTemplate {
 
         Ok(())
     }
+
+    /// Populates tests for extern functions.
+    ///
+    /// It also keeps track of the names of each test.
+    fn populate_foreign_fn_tests(
+        &mut self,
+        helper: &TranslateHelper,
+    ) -> Result<(), TranslationError> {
+        let should_skip_fn_test = |ident| {
+            helper
+                .generator
+                .skip_fn_ptrcheck
+                .as_ref()
+                .is_some_and(|skip| skip(ident))
+        };
+        for func in helper.ffi_items.foreign_functions() {
+            if should_skip_fn_test(func.ident()) {
+                continue;
+            }
+
+            let item = TestForeignFn {
+                test_name: foreign_fn_test_ident(func.ident()),
+                id: func.ident().into(),
+                c_val: helper.c_ident(func).into_boxed_str(),
+            };
+
+            self.foreign_fn_tests.push(item.clone());
+            self.test_idents.push(item.test_name);
+        }
+
+        Ok(())
+    }
 }
 
 /* Many test structures have the following fields:
@@ -457,6 +491,13 @@ pub(crate) struct TestRoundtrip {
     pub is_alias: bool,
 }
 
+#[derive(Clone, Debug)]
+pub(crate) struct TestForeignFn {
+    pub test_name: BoxStr,
+    pub c_val: BoxStr,
+    pub id: BoxStr,
+}
+
 fn signededness_test_ident(ident: &str) -> BoxStr {
     format!("ctest_signededness_{ident}").into()
 }
@@ -485,6 +526,10 @@ fn roundtrip_test_ident(ident: &str) -> BoxStr {
     format!("ctest_roundtrip_{ident}").into()
 }
 
+fn foreign_fn_test_ident(ident: &str) -> BoxStr {
+    format!("ctest_foreign_fn_{ident}").into()
+}
+
 /// Wrap methods that depend on both ffi items and the generator.
 pub(crate) struct TranslateHelper<'a> {
     ffi_items: &'a FfiItems,
@@ -533,7 +578,7 @@ impl<'a> TranslateHelper<'a> {
 
         let ty = cdecl::cdecl(&ty, "".to_string()).map_err(|_| {
             TranslationError::new(
-                crate::translator::TranslationErrorKind::InvalidReturn,
+                TranslationErrorKind::InvalidReturn,
                 ident,
                 Span::call_site(),
             )

ctest-next/src/tests.rs

@@ -2,7 +2,7 @@ use syn::spanned::Spanned;
 use syn::visit::Visit;
 
 use crate::ffi_items::FfiItems;
-use crate::translator::Translator;
+use crate::translator::{TranslationErrorKind, Translator};
 use crate::{Result, TestGenerator, TranslationError, cdecl};
 
 const ALL_ITEMS: &str = r#"
@@ -44,13 +44,13 @@ fn r2cdecl(s: &str, name: &str) -> Result<String, TranslationError> {
     let translator = Translator::new(&ffi_items, &generator);
     let ty: syn::Type = syn::parse_str(s).unwrap();
     let translated = translator.translate_type(&ty)?;
-    cdecl::cdecl(&translated, name.to_string()).map_err(|_| {
-        TranslationError::new(
-            crate::translator::TranslationErrorKind::InvalidReturn,
-            s,
-            ty.span(),
-        )
-    })
+    cdecl::cdecl(&translated, name.to_string())
+        .map_err(|_| TranslationError::new(TranslationErrorKind::InvalidReturn, s, ty.span()))
+}
+
+#[track_caller]
+fn assert_r2cdecl(rust: &str, expected: &str) {
+    assert_eq!(r2cdecl(rust, "foo").unwrap(), expected)
 }
 
 #[test]
@@ -70,55 +70,37 @@ fn test_extraction_ffi_items() {
 
 #[test]
 fn test_translation_type_ptr() {
-    assert_eq!(
-        r2cdecl("*const *mut i32", "").unwrap(),
-        "int32_t *const *".to_string()
-    );
-    assert_eq!(
-        r2cdecl("*const [u128; 2 + 3]", "").unwrap(),
-        "unsigned __int128 (*)[2 + 3]".to_string()
-    );
-    assert_eq!(
-        r2cdecl("*const *mut [u8; 5]", "").unwrap(),
-        "uint8_t (*const *)[5]".to_string()
-    );
+    assert_r2cdecl("*const *mut i32", "int32_t *const *foo");
+    assert_r2cdecl("*const [u128; 2 + 3]", "unsigned __int128 (*foo)[2 + 3]");
+    assert_r2cdecl("*const *mut [u8; 5]", "uint8_t (*const *foo)[5]");
+    assert_r2cdecl("*mut *const [u8; 5]", "uint8_t (**foo)[5]");
+    assert_r2cdecl("*const *const [u8; 5]", "uint8_t (*const *foo)[5]");
+    assert_r2cdecl("*mut *mut [u8; 5]", "uint8_t (**foo)[5]");
 }
 
 #[test]
 fn test_translation_type_reference() {
-    assert_eq!(r2cdecl("&u8", "").unwrap(), "const uint8_t *".to_string());
-    assert_eq!(
-        r2cdecl("&&u8", "").unwrap(),
-        "const uint8_t *const *".to_string()
-    );
-    assert_eq!(
-        r2cdecl("*mut &u8", "").unwrap(),
-        "const uint8_t **".to_string()
-    );
-    assert_eq!(
-        r2cdecl("& &mut u8", "").unwrap(),
-        "uint8_t *const *".to_string()
-    );
+    assert_r2cdecl("&u8", "const uint8_t *foo");
+    assert_r2cdecl("&&u8", "const uint8_t *const *foo");
+    assert_r2cdecl("*mut &u8", "const uint8_t **foo");
+    assert_r2cdecl("& &mut u8", "uint8_t *const *foo");
 }
 
 #[test]
 fn test_translation_type_bare_fn() {
-    assert_eq!(
-        r2cdecl("fn(*mut u8, i16) -> *const char", "").unwrap(),
-        "const char *(*)(uint8_t *, int16_t)".to_string()
+    assert_r2cdecl(
+        "fn(*mut u8, i16) -> *const char",
+        "const char *(*foo)(uint8_t *, int16_t)",
     );
-    assert_eq!(
-        r2cdecl("*const fn(*mut u8, &mut [u8; 16]) -> &mut *mut u8", "").unwrap(),
-        "uint8_t **(*const *)(uint8_t *, uint8_t (*)[16])".to_string()
+    assert_r2cdecl(
+        "*const fn(*mut u8, &mut [u8; 16]) -> &mut *mut u8",
+        "uint8_t **(*const *foo)(uint8_t *, uint8_t (*)[16])",
     );
 }
 
 #[test]
 fn test_translation_type_array() {
-    assert_eq!(
-        r2cdecl("[&u8; 2 + 2]", "").unwrap(),
-        "const uint8_t *[2 + 2]".to_string()
-    );
+    assert_r2cdecl("[&u8; 2 + 2]", "const uint8_t *foo[2 + 2]");
 }
 
 #[test]
@@ -129,25 +111,19 @@ fn test_translation_fails_for_unsupported() {
 
 #[test]
 fn test_translate_helper_function_pointer() {
-    assert_eq!(
-        r2cdecl("extern \"C\" fn(c_int) -> *const c_void", "test_make_cdecl").unwrap(),
-        "const void *(*test_make_cdecl)(int)"
+    assert_r2cdecl(
+        "extern \"C\" fn(c_int) -> *const c_void",
+        "const void *(*foo)(int)",
     );
     // FIXME(ctest): Reimplement support for ABI in a more robust way.
-    // assert_eq!(
-    //     cdecl("Option<extern \"stdcall\" fn(*const c_char, [u32; 16]) -> u8>").unwrap(),
-    //     "uint8_t (__stdcall **test_make_cdecl)(const char *, uint32_t [16])"
+    // assert_r2cdecl(
+    //     "Option<extern \"stdcall\" fn(*const c_char, [u32; 16]) -> u8>",
+    //     "uint8_t (__stdcall **foo)(const char *, uint32_t [16])"
     // );
 }
 
 #[test]
 fn test_translate_helper_array_1d_2d() {
-    assert_eq!(
-        r2cdecl("[u8; 10]", "test_make_cdecl").unwrap(),
-        "uint8_t test_make_cdecl[10]",
-    );
-    assert_eq!(
-        r2cdecl("[[u8; 64]; 32]", "test_make_cdecl").unwrap(),
-        "uint8_t test_make_cdecl[32][64]"
-    );
+    assert_r2cdecl("[u8; 10]", "uint8_t foo[10]");
+    assert_r2cdecl("[[u8; 64]; 32]", "uint8_t foo[32][64]");
 }

ctest-next/src/translator.rs

@@ -178,7 +178,7 @@ impl<'a> Translator<'a> {
     }
 
     /// Translate a Rust function pointer type to its C equivalent.
-    fn translate_bare_fn(
+    pub(crate) fn translate_bare_fn(
         &self,
         function: &syn::TypeBareFn,
     ) -> Result<cdecl::CTy, TranslationError> {

ctest-next/templates/test.c

@@ -13,6 +13,8 @@
 #include <{{ header }}>
 {%- endfor +%}
 
+typedef void (*ctest_void_func)(void);
+
 {%- for const_cstr in ctx.const_cstr_tests +%}
 
 static char *ctest_const_{{ const_cstr.id }}_val_static = {{ const_cstr.c_val }};
@@ -118,3 +120,20 @@ ctest_field_ptr__{{ item.id }}__{{ item.field.ident() }}({{ item.c_ty }} *b) {
 #ifdef _MSC_VER
 #  pragma warning(default:4365)
 #endif
+
+#ifdef _MSC_VER
+// Disable function pointer type conversion warnings on MSVC.
+// The conversion may fail only if we call that function, however we only check its address.
+#  pragma warning(disable:4191)
+#endif
+
+{%- for item in ctx.foreign_fn_tests +%}
+
+ctest_void_func ctest_foreign_fn__{{ item.id }}(void) {
+    return (ctest_void_func){{ item.c_val }};
+}
+{%- endfor +%}
+
+#ifdef _MSC_VER
+#  pragma warning(default:4191)
+#endif

ctest-next/templates/test.rs

@@ -314,6 +314,19 @@ mod generated_tests {
         }
     }
 {%- endfor +%}
+
+{%- for item in ctx.foreign_fn_tests +%}
+
+    /// Check if the Rust and C side function pointers point to the same underlying function.
+    pub fn {{ item.test_name }}() {
+        extern "C" {
+            fn ctest_foreign_fn__{{ item.id }}() -> unsafe extern "C" fn();
+        }
+        let actual = unsafe { ctest_foreign_fn__{{ item.id }}() } as u64;
+        let expected = {{ item.id }} as u64;
+        check_same(actual, expected, "{{ item.id }} function pointer");
+    }
+{%- endfor +%}
 }
 
 use generated_tests::*;