Allow generating hidden visibility functions

bindgen-tests/tests/tests.rs

@@ -427,6 +427,49 @@ fn test_header_contents() {
     assert_eq!(expected, actual);
 }
 
+const HIDDEN_FUNCTIONS_HEADER: &str = r#"
+__attribute__((visibility("hidden"))) int hidden_fn(void);
+__attribute__((visibility("protected"))) int protected_fn(void);
+int visible_fn(void);
+"#;
+
+fn hidden_functions_builder() -> Builder {
+    builder()
+        .allowlist_function("visible_fn")
+        .allowlist_function("hidden_fn")
+        .allowlist_function("protected_fn")
+        .header_contents("hidden.h", HIDDEN_FUNCTIONS_HEADER)
+}
+
+#[test]
+fn hidden_functions_are_skipped_by_default() {
+    let bindings = hidden_functions_builder().generate().unwrap().to_string();
+
+    assert!(bindings.contains("pub fn visible_fn"));
+    assert!(!bindings.contains("pub fn hidden_fn"));
+}
+
+#[test]
+fn hidden_functions_can_be_generated_when_enabled() {
+    let default_bindings =
+        hidden_functions_builder().generate().unwrap().to_string();
+
+    let hidden_enabled = hidden_functions_builder()
+        .generate_hidden_functions(true)
+        .generate()
+        .unwrap()
+        .to_string();
+
+    assert!(hidden_enabled.contains("pub fn hidden_fn"));
+    assert!(!default_bindings.contains("pub fn hidden_fn"));
+
+    // Clang on Mach-O downgrades `protected` visibility to `default`,
+    // so the symbol might already be present without the new option.
+    if !default_bindings.contains("pub fn protected_fn") {
+        assert!(hidden_enabled.contains("pub fn protected_fn"));
+    }
+}
+
 #[test]
 fn test_multiple_header_calls_in_builder() {
     let actual = builder()

bindgen/ir/function.rs

@@ -730,7 +730,11 @@ impl ClangSubItemParser for Function {
 
         debug!("Function::parse({cursor:?}, {:?})", cursor.cur_type());
         let visibility = cursor.visibility();
-        if visibility != CXVisibility_Default {
+        let allow_hidden = context.options().generate_hidden_functions &&
+            (visibility == CXVisibility_Hidden ||
+                visibility == CXVisibility_Protected);
+
+        if visibility != CXVisibility_Default && !allow_hidden {
             return Err(ParseError::Continue);
         }
         if cursor.access_specifier() == CX_CXXPrivate &&

bindgen/options/mod.rs

@@ -2329,4 +2329,16 @@ options! {
         },
         as_args: "--generate-private-functions",
     },
+    /// Whether to allow generating functions that are marked with hidden or protected visibility.
+    generate_hidden_functions: bool {
+        methods: {
+            /// Set whether to generate functions that are not externally visible according to clang.
+            pub fn generate_hidden_functions(mut self, doit: bool) -> Self {
+                self.options.generate_hidden_functions = doit;
+                self
+            }
+
+        },
+        as_args: "--generate-hidden-functions",
+    },
 }