Add support for --wrap-extern-fns to bindgen rules (#2743)

bindgen/private/bindgen.bzl

@@ -18,7 +18,7 @@ load(
     "@bazel_tools//tools/build_defs/cc:action_names.bzl",
     "CPP_COMPILE_ACTION_NAME",
 )
-load("@rules_cc//cc:defs.bzl", "CcInfo")
+load("@rules_cc//cc:defs.bzl", "CcInfo", "cc_library")
 load("//rust:defs.bzl", "rust_library")
 load("//rust:rust_common.bzl", "BuildInfo")
 
@@ -48,6 +48,7 @@ def rust_bindgen_library(
         bindgen_flags = None,
         bindgen_features = None,
         clang_flags = None,
+        wrap_static_fns = False,
         **kwargs):
     """Generates a rust source file for `header`, and builds a rust_library.
 
@@ -60,6 +61,7 @@ def rust_bindgen_library(
         bindgen_flags (list, optional): Flags to pass directly to the bindgen executable. See https://rust-lang.github.io/rust-bindgen/ for details.
         bindgen_features (list, optional): The `features` attribute for the `rust_bindgen` target.
         clang_flags (list, optional): Flags to pass directly to the clang executable.
+        wrap_static_fns (bool): Whether to create a separate .c file for static fns. Requires nightly toolchain, and a header that actually needs this feature (otherwise bindgen won't generate the file and Bazel complains",
         **kwargs: Arguments to forward to the underlying `rust_library` rule.
     """
 
@@ -85,6 +87,7 @@ def rust_bindgen_library(
         features = bindgen_features,
         clang_flags = clang_flags or [],
         tags = sub_tags,
+        wrap_static_fns = wrap_static_fns,
         **bindgen_kwargs
     )
 
@@ -94,10 +97,23 @@ def rust_bindgen_library(
     if "deps" in kwargs:
         kwargs.pop("deps")
 
+    if wrap_static_fns:
+        native.filegroup(
+            name = name + "__bindgen_c_thunks",
+            srcs = [":" + name + "__bindgen"],
+            output_group = "bindgen_c_thunks",
+        )
+
+        cc_library(
+            name = name + "__bindgen_c_thunks_library",
+            srcs = [":" + name + "__bindgen_c_thunks"],
+            deps = [cc_lib],
+        )
+
     rust_library(
         name = name,
         srcs = [name + "__bindgen.rs"],
-        deps = deps + [name + "__bindgen"],
+        deps = deps + [":" + name + "__bindgen"] + ([":" + name + "__bindgen_c_thunks_library"] if wrap_static_fns else []),
         tags = tags,
         **kwargs
     )
@@ -203,6 +219,19 @@ def _rust_bindgen_impl(ctx):
     args.add(header)
     args.add("--output", output)
 
+    wrap_static_fns = getattr(ctx.attr, "wrap_static_fns", False)
+
+    c_output = None
+    if wrap_static_fns:
+        if "--wrap-static-fns" in ctx.attr.bindgen_flags:
+            fail("Do not pass `--wrap-static-fns` to `bindgen_flags, it's added automatically." +
+                 "The generated C file is accesible in the `bindgen_c_thunks` output group.")
+        c_output = ctx.actions.declare_file(ctx.label.name + ".bindgen_c_thunks.c")
+        args.add("--experimental")
+        args.add("--wrap-static-fns")
+        args.add("--wrap-static-fns-path")
+        args.add(c_output.path)
+
     # Vanilla usage of bindgen produces formatted output, here we do the same if we have `rustfmt` in our toolchain.
     rustfmt_toolchain = ctx.toolchains[Label("//rust/rustfmt:toolchain_type")]
     if toolchain.default_rustfmt:
@@ -279,7 +308,7 @@ def _rust_bindgen_impl(ctx):
                 _get_libs_for_static_executable(libstdcxx),
             ] if libstdcxx else []),
         ),
-        outputs = [output],
+        outputs = [output] + ([c_output] if wrap_static_fns else []),
         mnemonic = "RustBindgen",
         progress_message = "Generating bindings for {}..".format(header.path),
         env = env,
@@ -305,6 +334,7 @@ def _rust_bindgen_impl(ctx):
         ),
         OutputGroupInfo(
             bindgen_bindings = depset([output]),
+            bindgen_c_thunks = depset(([c_output] if wrap_static_fns else [])),
         ),
     ]
 
@@ -328,6 +358,10 @@ rust_bindgen = rule(
             allow_single_file = True,
             mandatory = True,
         ),
+        "wrap_static_fns": attr.bool(
+            doc = "Whether to create a separate .c file for static fns. Requires nightly toolchain, and a header that actually needs this feature (otherwise bindgen won't generate the file and Bazel complains).",
+            default = False,
+        ),
         "_cc_toolchain": attr.label(
             default = Label("@bazel_tools//tools/cpp:current_cc_toolchain"),
         ),

docs/flatten.md

@@ -327,7 +327,7 @@ is available under the key `dsym_folder` in `OutputGroupInfo`.
 ## rust_bindgen
 
 <pre>
-rust_bindgen(<a href="#rust_bindgen-name">name</a>, <a href="#rust_bindgen-bindgen_flags">bindgen_flags</a>, <a href="#rust_bindgen-cc_lib">cc_lib</a>, <a href="#rust_bindgen-clang_flags">clang_flags</a>, <a href="#rust_bindgen-header">header</a>)
+rust_bindgen(<a href="#rust_bindgen-name">name</a>, <a href="#rust_bindgen-bindgen_flags">bindgen_flags</a>, <a href="#rust_bindgen-cc_lib">cc_lib</a>, <a href="#rust_bindgen-clang_flags">clang_flags</a>, <a href="#rust_bindgen-header">header</a>, <a href="#rust_bindgen-wrap_static_fns">wrap_static_fns</a>)
 </pre>
 
 Generates a rust source file from a cc_library and a header.
@@ -342,6 +342,7 @@ Generates a rust source file from a cc_library and a header.
 | <a id="rust_bindgen-cc_lib"></a>cc_lib |  The cc_library that contains the `.h` file. This is used to find the transitive includes.   | <a href="https://bazel.build/concepts/labels">Label</a> | required |  |
 | <a id="rust_bindgen-clang_flags"></a>clang_flags |  Flags to pass directly to the clang executable.   | List of strings | optional |  `[]`  |
 | <a id="rust_bindgen-header"></a>header |  The `.h` file to generate bindings for.   | <a href="https://bazel.build/concepts/labels">Label</a> | required |  |
+| <a id="rust_bindgen-wrap_static_fns"></a>wrap_static_fns |  Whether to create a separate .c file for static fns. Requires nightly toolchain, and a header that actually needs this feature (otherwise bindgen won't generate the file and Bazel complains).   | Boolean | optional |  `False`  |
 
 
 <a id="rust_bindgen_toolchain"></a>
@@ -1668,7 +1669,8 @@ list[struct(repo=str, is_dev_dep=bool)]: A list of the repositories
 ## rust_bindgen_library
 
 <pre>
-rust_bindgen_library(<a href="#rust_bindgen_library-name">name</a>, <a href="#rust_bindgen_library-header">header</a>, <a href="#rust_bindgen_library-cc_lib">cc_lib</a>, <a href="#rust_bindgen_library-bindgen_flags">bindgen_flags</a>, <a href="#rust_bindgen_library-bindgen_features">bindgen_features</a>, <a href="#rust_bindgen_library-clang_flags">clang_flags</a>, <a href="#rust_bindgen_library-kwargs">kwargs</a>)
+rust_bindgen_library(<a href="#rust_bindgen_library-name">name</a>, <a href="#rust_bindgen_library-header">header</a>, <a href="#rust_bindgen_library-cc_lib">cc_lib</a>, <a href="#rust_bindgen_library-bindgen_flags">bindgen_flags</a>, <a href="#rust_bindgen_library-bindgen_features">bindgen_features</a>, <a href="#rust_bindgen_library-clang_flags">clang_flags</a>,
+                     <a href="#rust_bindgen_library-wrap_static_fns">wrap_static_fns</a>, <a href="#rust_bindgen_library-kwargs">kwargs</a>)
 </pre>
 
 Generates a rust source file for `header`, and builds a rust_library.
@@ -1687,6 +1689,7 @@ Arguments are the same as `rust_bindgen`, and `kwargs` are passed directly to ru
 | <a id="rust_bindgen_library-bindgen_flags"></a>bindgen_flags |  Flags to pass directly to the bindgen executable. See https://rust-lang.github.io/rust-bindgen/ for details.   |  `None` |
 | <a id="rust_bindgen_library-bindgen_features"></a>bindgen_features |  The `features` attribute for the `rust_bindgen` target.   |  `None` |
 | <a id="rust_bindgen_library-clang_flags"></a>clang_flags |  Flags to pass directly to the clang executable.   |  `None` |
+| <a id="rust_bindgen_library-wrap_static_fns"></a>wrap_static_fns |  Whether to create a separate .c file for static fns. Requires nightly toolchain, and a header that actually needs this feature (otherwise bindgen won't generate the file and Bazel complains",   |  `False` |
 | <a id="rust_bindgen_library-kwargs"></a>kwargs |  Arguments to forward to the underlying `rust_library` rule.   |  none |
 
 

docs/rust_bindgen.md

@@ -53,7 +53,7 @@ toolchains following the instructions for [rust_bindgen_toolchain](#rust_bindgen
 ## rust_bindgen
 
 <pre>
-rust_bindgen(<a href="#rust_bindgen-name">name</a>, <a href="#rust_bindgen-bindgen_flags">bindgen_flags</a>, <a href="#rust_bindgen-cc_lib">cc_lib</a>, <a href="#rust_bindgen-clang_flags">clang_flags</a>, <a href="#rust_bindgen-header">header</a>)
+rust_bindgen(<a href="#rust_bindgen-name">name</a>, <a href="#rust_bindgen-bindgen_flags">bindgen_flags</a>, <a href="#rust_bindgen-cc_lib">cc_lib</a>, <a href="#rust_bindgen-clang_flags">clang_flags</a>, <a href="#rust_bindgen-header">header</a>, <a href="#rust_bindgen-wrap_static_fns">wrap_static_fns</a>)
 </pre>
 
 Generates a rust source file from a cc_library and a header.
@@ -68,6 +68,7 @@ Generates a rust source file from a cc_library and a header.
 | <a id="rust_bindgen-cc_lib"></a>cc_lib |  The cc_library that contains the `.h` file. This is used to find the transitive includes.   | <a href="https://bazel.build/concepts/labels">Label</a> | required |  |
 | <a id="rust_bindgen-clang_flags"></a>clang_flags |  Flags to pass directly to the clang executable.   | List of strings | optional |  `[]`  |
 | <a id="rust_bindgen-header"></a>header |  The `.h` file to generate bindings for.   | <a href="https://bazel.build/concepts/labels">Label</a> | required |  |
+| <a id="rust_bindgen-wrap_static_fns"></a>wrap_static_fns |  Whether to create a separate .c file for static fns. Requires nightly toolchain, and a header that actually needs this feature (otherwise bindgen won't generate the file and Bazel complains).   | Boolean | optional |  `False`  |
 
 
 <a id="rust_bindgen_toolchain"></a>
@@ -140,7 +141,8 @@ list[struct(repo=str, is_dev_dep=bool)]: A list of the repositories
 ## rust_bindgen_library
 
 <pre>
-rust_bindgen_library(<a href="#rust_bindgen_library-name">name</a>, <a href="#rust_bindgen_library-header">header</a>, <a href="#rust_bindgen_library-cc_lib">cc_lib</a>, <a href="#rust_bindgen_library-bindgen_flags">bindgen_flags</a>, <a href="#rust_bindgen_library-bindgen_features">bindgen_features</a>, <a href="#rust_bindgen_library-clang_flags">clang_flags</a>, <a href="#rust_bindgen_library-kwargs">kwargs</a>)
+rust_bindgen_library(<a href="#rust_bindgen_library-name">name</a>, <a href="#rust_bindgen_library-header">header</a>, <a href="#rust_bindgen_library-cc_lib">cc_lib</a>, <a href="#rust_bindgen_library-bindgen_flags">bindgen_flags</a>, <a href="#rust_bindgen_library-bindgen_features">bindgen_features</a>, <a href="#rust_bindgen_library-clang_flags">clang_flags</a>,
+                     <a href="#rust_bindgen_library-wrap_static_fns">wrap_static_fns</a>, <a href="#rust_bindgen_library-kwargs">kwargs</a>)
 </pre>
 
 Generates a rust source file for `header`, and builds a rust_library.
@@ -159,6 +161,7 @@ Arguments are the same as `rust_bindgen`, and `kwargs` are passed directly to ru
 | <a id="rust_bindgen_library-bindgen_flags"></a>bindgen_flags |  Flags to pass directly to the bindgen executable. See https://rust-lang.github.io/rust-bindgen/ for details.   |  `None` |
 | <a id="rust_bindgen_library-bindgen_features"></a>bindgen_features |  The `features` attribute for the `rust_bindgen` target.   |  `None` |
 | <a id="rust_bindgen_library-clang_flags"></a>clang_flags |  Flags to pass directly to the clang executable.   |  `None` |
+| <a id="rust_bindgen_library-wrap_static_fns"></a>wrap_static_fns |  Whether to create a separate .c file for static fns. Requires nightly toolchain, and a header that actually needs this feature (otherwise bindgen won't generate the file and Bazel complains",   |  `False` |
 | <a id="rust_bindgen_library-kwargs"></a>kwargs |  Arguments to forward to the underlying `rust_library` rule.   |  none |
 
 

examples/bindgen/BUILD.bazel

@@ -9,6 +9,7 @@ rust_bindgen_library(
     ],
     cc_lib = "//bindgen/simple",
     header = "//bindgen/simple:simple.h",
+    wrap_static_fns = True,
 )
 
 rust_binary(

examples/bindgen/main.rs

@@ -4,11 +4,16 @@ fn simple_function() -> i64 {
     unsafe { simple_bindgen::simple_function() }
 }
 
+fn simple_static_function() -> i64 {
+    unsafe { simple_bindgen::simple_static_function() }
+}
+
 fn main() {
     println!(
-        "The values are {} and {}!",
+        "The values are {}, {}, and {}!",
         simple_bindgen::SIMPLE_VALUE,
-        simple_function()
+        simple_function(),
+        simple_static_function(),
     );
 }
 
@@ -18,5 +23,6 @@ mod test {
     fn do_the_test() {
         assert_eq!(42, simple_bindgen::SIMPLE_VALUE);
         assert_eq!(1337, super::simple_function());
+        assert_eq!(84, super::simple_static_function());
     }
 }

examples/bindgen/simple/simple.h

@@ -9,8 +9,10 @@
 
 #include <stdint.h>
 
-EXTERN_C const int64_t SIMPLE_VALUE = 42;
+static const int64_t SIMPLE_VALUE = 42;
 
 EXTERN_C const int64_t simple_function();
 
+static inline int64_t simple_static_function() { return 84; }
+
 #endif