Wrap va_list function as variadic function (#2502)

* Add more generic version of fnsig_arguments based on iterator

* Wrap va_list function as variadic function

* Add tests for wrapped va_list fn as variadic

* Add tests for wrapped va_list in bindgen-integration

* Make an exception for including stdarg.h in the tests

* Add wrap_as_variadic_fn in the CHANGELOG.md

CHANGELOG.md

@@ -170,6 +170,8 @@
   instead of `&[u8]`. (Requires Rust 1.59 or higher.)
 * Added the `--generate-shell-completions` CLI flag to generate completions for
   different shells.
+* The `--wrap-static-fns` option can now wrap `va_list` functions as variadic functions
+  with the experimental `wrap_as_variadic_fn` callback.
 
 ## Changed
 

bindgen-integration/build.rs

@@ -149,6 +149,15 @@ impl Drop for MacroCallback {
     }
 }
 
+#[derive(Debug)]
+struct WrappedVaListCallback;
+
+impl ParseCallbacks for WrappedVaListCallback {
+    fn wrap_as_variadic_fn(&self, name: &str) -> Option<String> {
+        Some(name.to_owned() + "_wrapped")
+    }
+}
+
 fn setup_macro_test() {
     cc::Build::new()
         .cpp(true)
@@ -223,10 +232,12 @@ fn setup_wrap_static_fns_test() {
     let bindings = Builder::default()
         .header(input_header_file_path_str)
         .parse_callbacks(Box::new(CargoCallbacks))
+        .parse_callbacks(Box::new(WrappedVaListCallback))
         .wrap_static_fns(true)
         .wrap_static_fns_path(
             out_path.join("wrap_static_fns").display().to_string(),
         )
+        .clang_arg("-DUSE_VA_HEADER")
         .generate()
         .expect("Unable to generate bindings");
 
@@ -242,6 +253,7 @@ fn setup_wrap_static_fns_test() {
         .arg("-o")
         .arg(&obj_path)
         .arg(out_path.join("wrap_static_fns.c"))
+        .arg("-DUSE_VA_HEADER")
         .output()
         .expect("`clang` command error");
     if !clang_output.status.success() {

bindgen-integration/src/lib.rs

@@ -320,5 +320,13 @@ fn test_wrap_static_fns() {
         let tq =
             extern_bindings::takes_qualified(&(&5 as *const _) as *const _);
         assert_eq!(5, tq);
+
+        let wv1 = extern_bindings::wrap_as_variadic_fn1_wrapped(0);
+        assert_eq!(0, wv1);
+
+        let wv1 = extern_bindings::wrap_as_variadic_fn1_wrapped(2, 5, 3);
+        assert_eq!(8, wv1);
+
+        extern_bindings::wrap_as_variadic_fn2_wrapped(1, 2);
     }
 }

bindgen-tests/tests/expectations/tests/generated/wrap_static_fns.c

@@ -11,3 +11,21 @@ int takes_alias__extern(func f) { return takes_alias(f); }
 int takes_qualified__extern(const int *const *arg) { return takes_qualified(arg); }
 enum foo takes_enum__extern(const enum foo f) { return takes_enum(f); }
 void nevermore__extern(void) { nevermore(); }
+void no_extra_argument__extern(__builtin_va_list va) { no_extra_argument(va); }
+int many_va_list__extern(int i, __builtin_va_list va1, __builtin_va_list va2) { return many_va_list(i, va1, va2); }
+int wrap_as_variadic_fn1__extern(int i, ...) {
+    int ret;
+    va_list ap;
+
+    va_start(ap, i);
+    ret = wrap_as_variadic_fn1(i, ap);
+    va_end(ap);
+    return ret;
+}
+void wrap_as_variadic_fn2__extern(int i, ...) {
+    va_list ap;
+
+    va_start(ap, i);
+    wrap_as_variadic_fn2(i, ap);
+    va_end(ap);
+}

bindgen-tests/tests/headers/wrap-static-fns.h

@@ -1,4 +1,11 @@
 // bindgen-flags: --experimental --wrap-static-fns
+// bindgen-parse-callbacks: wrap-as-variadic-fn
+
+// to avoid poluting theexpectation tests we put the stdarg.h behind a conditional
+// variable only used in bindgen-integration
+#ifdef USE_VA_HEADER
+#include <stdarg.h>
+#endif
 
 static inline int foo() {
     return 11;
@@ -48,3 +55,28 @@ static inline void nevermore() {
 static inline int variadic(int x, ...) {
     return x;
 }
+
+static inline void no_extra_argument(__builtin_va_list va) {}
+
+static inline int many_va_list(int i, __builtin_va_list va1, __builtin_va_list va2) {
+    return i;
+}
+
+#ifndef USE_VA_HEADER
+static inline int wrap_as_variadic_fn1(int i, __builtin_va_list va) {
+    return i;
+}
+
+static inline void wrap_as_variadic_fn2(int i, __builtin_va_list va) {}
+#else
+static inline int wrap_as_variadic_fn1(int i, va_list va) {
+    int res = 0;
+
+    for (int j = 0; j < i; j++)
+        res += (int) va_arg(va, int);
+
+    return res;
+}
+
+static inline void wrap_as_variadic_fn2(int i, va_list va) {}
+#endif

bindgen-tests/tests/parse_callbacks/mod.rs

@@ -113,6 +113,15 @@ impl ParseCallbacks for FieldVisibility {
     }
 }
 
+#[derive(Debug)]
+pub(super) struct WrapAsVariadicFn;
+
+impl ParseCallbacks for WrapAsVariadicFn {
+    fn wrap_as_variadic_fn(&self, name: &str) -> Option<String> {
+        Some(name.to_owned() + "_wrapped")
+    }
+}
+
 pub fn lookup(cb: &str) -> Box<dyn ParseCallbacks> {
     fn try_strip_prefix<'a>(s: &'a str, prefix: &str) -> Option<&'a str> {
         if s.starts_with(prefix) {
@@ -127,6 +136,7 @@ pub fn lookup(cb: &str) -> Box<dyn ParseCallbacks> {
         "blocklisted-type-implements-trait" => {
             Box::new(BlocklistedTypeImplementsTrait)
         }
+        "wrap-as-variadic-fn" => Box::new(WrapAsVariadicFn),
         call_back => {
             if let Some(prefix) =
                 try_strip_prefix(call_back, "remove-function-prefix-")

bindgen-tests/tests/tests.rs

@@ -618,6 +618,7 @@ fn test_wrap_static_fns() {
         .header("tests/headers/wrap-static-fns.h")
         .wrap_static_fns(true)
         .wrap_static_fns_path(generated_path.display().to_string())
+        .parse_callbacks(Box::new(parse_callbacks::WrapAsVariadicFn))
         .generate()
         .expect("Failed to generate bindings");
 

bindgen/callbacks.rs

@@ -146,6 +146,16 @@ pub trait ParseCallbacks: fmt::Debug {
     ) -> Option<crate::FieldVisibilityKind> {
         None
     }
+
+    /// Process a function name that as exactly one `va_list` argument
+    /// to be wrapped as a variadic function with the wrapped static function
+    /// feature.
+    ///
+    /// The returned string is new function name.
+    #[cfg(feature = "experimental")]
+    fn wrap_as_variadic_fn(&self, _name: &str) -> Option<String> {
+        None
+    }
 }
 
 /// Relevant information about a type to which new derive attributes will be added using