Generate extern wrappers for inlined functions (#2335)

* Generate extern wrappers for inlined functions

If bindgen finds an inlined function and the
`--generate-extern-functions` options is enabled, then:

- It will generate two new source and header files with external
  functions that wrap the inlined functions.
- Rerun `Bindings::generate` using the new header file to include these
  wrappers in the generated bindings.

The following additional options were added:
- `--extern-function-suffix=<suffix>`: Adds <suffix> to the name of each
  external wrapper function (`__extern` is used by default).
- `--extern-functions-file-name=<name>`: Uses <name> as the file name
  for the header and source files (`extern` is used by default).
- `--extern-function-directory=<dir>`: Creates the source and header
  files inside <dir> (`/tmp/bindgen` is used by default).

The C code serialization is experimental and only supports a very
limited set of C functions.

Fixes #1090.

---------

Co-authored-by: Amanjeev Sethi <aj@amanjeev.com>

bindgen-cli/Cargo.toml

@@ -21,7 +21,7 @@ path = "main.rs"
 name = "bindgen"
 
 [dependencies]
-bindgen = { path = "../bindgen", version = "=0.63.0", features = ["cli"] }
+bindgen = { path = "../bindgen", version = "=0.63.0", features = ["cli", "experimental"] }
 shlex = "1"
 clap = { version = "4", features = ["derive"] }
 env_logger = { version = "0.9.0", optional = true }

bindgen-cli/options.rs

@@ -353,6 +353,20 @@ struct BindgenCommand {
     /// Derive custom traits on a `union`. The <CUSTOM> value must be of the shape <REGEX>=<DERIVE> where <DERIVE> is a coma-separated list of derive macros.
     #[arg(long, value_name = "CUSTOM")]
     with_derive_custom_union: Vec<String>,
+    /// Generate wrappers for `static` and `static inline` functions.
+    #[arg(long, requires = "experimental")]
+    wrap_static_fns: bool,
+    /// Sets the path for the source file that must be created due to the presence of `static` and
+    /// `static inline` functions.
+    #[arg(long, requires = "experimental", value_name = "PATH")]
+    wrap_static_fns_path: Option<PathBuf>,
+    /// Sets the suffix added to the extern wrapper functions generated for `static` and `static
+    /// inline` functions.
+    #[arg(long, requires = "experimental", value_name = "SUFFIX")]
+    wrap_static_fns_suffix: Option<String>,
+    /// Enables experimental features.
+    #[arg(long)]
+    experimental: bool,
     /// Prints the version, and exits
     #[arg(short = 'V', long)]
     version: bool,
@@ -473,6 +487,10 @@ where
         with_derive_custom_struct,
         with_derive_custom_enum,
         with_derive_custom_union,
+        wrap_static_fns,
+        wrap_static_fns_path,
+        wrap_static_fns_suffix,
+        experimental: _,
         version,
         clang_args,
     } = command;
@@ -978,5 +996,17 @@ where
         }
     }
 
+    if wrap_static_fns {
+        builder = builder.wrap_static_fns(true);
+    }
+
+    if let Some(path) = wrap_static_fns_path {
+        builder = builder.wrap_static_fns_path(path);
+    }
+
+    if let Some(suffix) = wrap_static_fns_suffix {
+        builder = builder.wrap_static_fns_suffix(suffix);
+    }
+
     Ok((builder, output, verbose))
 }

bindgen-integration/Cargo.toml

@@ -7,7 +7,7 @@ publish = false
 build = "build.rs"
 
 [build-dependencies]
-bindgen = { path = "../bindgen" }
+bindgen = { path = "../bindgen", features = ["experimental"] }
 cc = "1.0"
 
 [features]

bindgen-integration/build.rs

@@ -4,7 +4,7 @@ extern crate cc;
 use bindgen::callbacks::{
     DeriveInfo, IntKind, MacroParsingBehavior, ParseCallbacks,
 };
-use bindgen::{Builder, EnumVariation};
+use bindgen::{Builder, CargoCallbacks, EnumVariation};
 use std::collections::HashSet;
 use std::env;
 use std::path::PathBuf;
@@ -28,21 +28,14 @@ impl ParseCallbacks for MacroCallback {
         MacroParsingBehavior::Default
     }
 
-    fn item_name(&self, original_item_name: &str) -> Option<String> {
-        if original_item_name.starts_with("my_prefixed_") {
-            Some(
-                original_item_name
-                    .trim_start_matches("my_prefixed_")
-                    .to_string(),
-            )
-        } else if original_item_name.starts_with("MY_PREFIXED_") {
-            Some(
-                original_item_name
-                    .trim_start_matches("MY_PREFIXED_")
-                    .to_string(),
-            )
-        } else {
-            None
+    fn int_macro(&self, name: &str, _value: i64) -> Option<IntKind> {
+        match name {
+            "TESTMACRO_CUSTOMINTKIND_PATH" => Some(IntKind::Custom {
+                name: "crate::MacroInteger",
+                is_signed: true,
+            }),
+
+            _ => None,
         }
     }
 
@@ -67,17 +60,6 @@ impl ParseCallbacks for MacroCallback {
         }
     }
 
-    fn int_macro(&self, name: &str, _value: i64) -> Option<IntKind> {
-        match name {
-            "TESTMACRO_CUSTOMINTKIND_PATH" => Some(IntKind::Custom {
-                name: "crate::MacroInteger",
-                is_signed: true,
-            }),
-
-            _ => None,
-        }
-    }
-
     fn func_macro(&self, name: &str, value: &[&[u8]]) {
         match name {
             "TESTMACRO_NONFUNCTIONAL" => {
@@ -122,6 +104,24 @@ impl ParseCallbacks for MacroCallback {
         }
     }
 
+    fn item_name(&self, original_item_name: &str) -> Option<String> {
+        if original_item_name.starts_with("my_prefixed_") {
+            Some(
+                original_item_name
+                    .trim_start_matches("my_prefixed_")
+                    .to_string(),
+            )
+        } else if original_item_name.starts_with("MY_PREFIXED_") {
+            Some(
+                original_item_name
+                    .trim_start_matches("MY_PREFIXED_")
+                    .to_string(),
+            )
+        } else {
+            None
+        }
+    }
+
     // Test the "custom derives" capability by adding `PartialEq` to the `Test` struct.
     fn add_derives(&self, info: &DeriveInfo<'_>) -> Vec<String> {
         if info.name == "Test" {
@@ -149,7 +149,7 @@ impl Drop for MacroCallback {
     }
 }
 
-fn main() {
+fn setup_macro_test() {
     cc::Build::new()
         .cpp(true)
         .file("cpp/Test.cc")
@@ -204,3 +204,75 @@ fn main() {
         "including stub via include dir must produce correct dep path",
     );
 }
+
+fn setup_wrap_static_fns_test() {
+    // GH-1090: https://github.com/rust-lang/rust-bindgen/issues/1090
+    // set output directory under /target so it is easy to clean generated files
+    let out_path = PathBuf::from(env::var("OUT_DIR").unwrap());
+    let out_rust_file = out_path.join("extern.rs");
+
+    let input_header_dir = PathBuf::from("../bindgen-tests/tests/headers/")
+        .canonicalize()
+        .expect("Cannot canonicalize libdir path");
+    let input_header_file_path = input_header_dir.join("wrap-static-fns.h");
+    let input_header_file_path_str = input_header_file_path
+        .to_str()
+        .expect("Path could not be converted to a str");
+
+    // generate external bindings with the external .c and .h files
+    let bindings = Builder::default()
+        .header(input_header_file_path_str)
+        .parse_callbacks(Box::new(CargoCallbacks))
+        .wrap_static_fns(true)
+        .wrap_static_fns_path(
+            out_path.join("wrap_static_fns").display().to_string(),
+        )
+        .generate()
+        .expect("Unable to generate bindings");
+
+    println!("cargo:rustc-link-lib=static=wrap_static_fns"); // tell cargo to link libextern
+    println!("bindings generated: {}", bindings);
+
+    let obj_path = out_path.join("wrap_static_fns.o");
+    let lib_path = out_path.join("libwrap_static_fns.a");
+
+    // build the external files to check if they work
+    let clang_output = std::process::Command::new("clang")
+        .arg("-c")
+        .arg("-o")
+        .arg(&obj_path)
+        .arg(out_path.join("wrap_static_fns.c"))
+        .arg("-include")
+        .arg(input_header_file_path)
+        .output()
+        .expect("`clang` command error");
+    if !clang_output.status.success() {
+        panic!(
+            "Could not compile object file:\n{}",
+            String::from_utf8_lossy(&clang_output.stderr)
+        );
+    }
+
+    let ar_output = std::process::Command::new("ar")
+        .arg("rcs")
+        .arg(lib_path)
+        .arg(obj_path)
+        .output()
+        .expect("`ar` command error");
+
+    if !ar_output.status.success() {
+        panic!(
+            "Could not emit library file:\n{}",
+            String::from_utf8_lossy(&ar_output.stderr)
+        );
+    }
+
+    bindings
+        .write_to_file(out_rust_file)
+        .expect("Cound not write bindings to the Rust file");
+}
+
+fn main() {
+    setup_macro_test();
+    setup_wrap_static_fns_test();
+}

bindgen-integration/src/lib.rs

@@ -4,6 +4,10 @@ mod bindings {
     include!(concat!(env!("OUT_DIR"), "/test.rs"));
 }
 
+mod extern_bindings {
+    include!(concat!(env!("OUT_DIR"), "/extern.rs"));
+}
+
 use std::ffi::CStr;
 use std::mem;
 use std::os::raw::c_int;
@@ -286,3 +290,35 @@ fn test_custom_derive() {
     assert!(meter < lightyear);
     assert!(meter > micron);
 }
+
+#[test]
+fn test_wrap_static_fns() {
+    // GH-1090: https://github.com/rust-lang/rust-bindgen/issues/1090
+    unsafe {
+        let f = extern_bindings::foo();
+        assert_eq!(11, f);
+
+        let b = extern_bindings::bar();
+        assert_eq!(1, b);
+
+        let t = extern_bindings::takes_ptr(&mut 1);
+        assert_eq!(2, t);
+
+        extern "C" fn function(x: i32) -> i32 {
+            x + 1
+        }
+
+        let tp = extern_bindings::takes_fn_ptr(Some(function));
+        assert_eq!(2, tp);
+
+        let tf = extern_bindings::takes_fn(Some(function));
+        assert_eq!(3, tf);
+
+        let ta = extern_bindings::takes_alias(Some(function));
+        assert_eq!(4, ta);
+
+        let tq =
+            extern_bindings::takes_qualified(&(&5 as *const _) as *const _);
+        assert_eq!(5, tq);
+    }
+}

bindgen-tests/Cargo.toml

@@ -5,7 +5,7 @@ version = "0.1.0"
 publish = false
 
 [dev-dependencies]
-bindgen = { path = "../bindgen", features = ["cli"] }
+bindgen = { path = "../bindgen", features = ["cli", "experimental"] }
 diff = "0.1"
 shlex = "1"
 clap = { version = "4", features = ["derive"] }

bindgen-tests/tests/expectations/tests/generated/README.md

@@ -0,0 +1,4 @@
+# Generated C, C++, Header files
+
+This directory contains files for features where extra files are generated
+as a part of the feature. For example, `--wrap-static-fns`.

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

@@ -0,0 +1,14 @@
+int foo__extern(void) asm("foo__extern");
+int foo__extern() { return foo(); }
+int bar__extern(void) asm("bar__extern");
+int bar__extern() { return bar(); }
+int takes_ptr__extern(int *arg) asm("takes_ptr__extern");
+int takes_ptr__extern(int *arg) { return takes_ptr(arg); }
+int takes_fn_ptr__extern(int (*f) (int)) asm("takes_fn_ptr__extern");
+int takes_fn_ptr__extern(int (*f) (int)) { return takes_fn_ptr(f); }
+int takes_fn__extern(int (f) (int)) asm("takes_fn__extern");
+int takes_fn__extern(int (f) (int)) { return takes_fn(f); }
+int takes_alias__extern(func f) asm("takes_alias__extern");
+int takes_alias__extern(func f) { return takes_alias(f); }
+int takes_qualified__extern(const int *const *arg) asm("takes_qualified__extern");
+int takes_qualified__extern(const int *const *arg) { return takes_qualified(arg); }

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

@@ -0,0 +1,33 @@
+// bindgen-flags: --experimental --wrap-static-fns
+
+static inline int foo() {
+    return 11;
+}
+static int bar() {
+    return 1;
+}
+inline int baz() {
+    return 2;
+}
+
+static inline int takes_ptr(int* arg) {
+    return *arg + 1;
+}
+
+static inline int takes_fn_ptr(int (*f)(int)) {
+    return f(1);
+}
+
+static inline int takes_fn(int (f)(int)) {
+    return f(2);
+}
+
+typedef int (func)(int);
+
+static inline int takes_alias(func f) {
+    return f(3);
+}
+
+static inline int takes_qualified(const int *const *arg) {
+    return **arg;
+}