On Mon, Jun 12, 2023 at 9:45 PM Aakash Sen Sharma <aakashsensharma@xxxxxxxxx> wrote: > > * Rationale: > > Upgrades bindgen to code-generation for anonymous unions, structs, and enums [7] > for LLVM-16 based toolchains. > > The following upgrade also incorporates `noreturn` support from bindgen > allowing us to remove useless `loop` calls which was placed as a > workaround. > > * Truncated build logs on using bindgen `v0.56.0` prior to LLVM-16 toolchain: > > ``` > $ make rustdoc LLVM=1 CLIPPY=1 -j$(nproc) > RUSTC L rust/core.o > BINDGEN rust/bindings/bindings_generated.rs > BINDGEN rust/bindings/bindings_helpers_generated.rs > BINDGEN rust/uapi/uapi_generated.rs > thread 'main' panicked at '"ftrace_branch_data_union_(anonymous_at__/_/include/linux/compiler_types_h_146_2)" is not a valid Ident', .../proc-macro2-1.0.24/src/fallback.rs:693:9 > ... > thread 'main' panicked at '"ftrace_branch_data_union_(anonymous_at__/_/include/linux/compiler_types_h_146_2)" is not a valid Ident', .../proc-macro2-1.0.24/src/fallback.rs:693:9 > ... > ``` > > * LLVM-16 Changes: > > API changes [1] were introduced such that libclang would emit names like > "(unnamed union at compiler_types.h:146:2)" for unnamed unions, structs, and > enums whereas it previously returned an empty string. > > * Bindgen Changes: > > Bindgen `v0.56.0` on LLVM-16 based toolchains hence was unable to process the > anonymous union in `include/linux/compiler_types` `struct ftrace_branch_data` > and caused subsequent panics as the new `libclang` API emitted name was not > being handled. The following issue was fixed in Bindgen `v0.62.0` [2]. > > Bindgen `v0.58.0` changed the flags `--whitelist-*` and `--blacklist-*` > to `--allowlist-*` and `--blocklist-*` respectively [3]. > > Bindgen `v0.61.0` added support for `_Noreturn`, `[[noreturn]]`, `__attribute__((noreturn))` [4], > hence the empty `loop`s used to circumvent bindgen returning `!` in place of `()` > for noreturn attributes have been removed completely. > > Bindgen `v0.61.0` also changed default functionality to bind `size_t` to `usize` [5] and > added the `--no-size_t-is-usize` [5] flag to not bind `size_t` as `usize`. > > Bindgen `v0.65.0` removed `--size_t-is-usize` flag [6]. > > Link: https://github.com/llvm/llvm-project/commit/19e984ef8f49bc3ccced15621989fa9703b2cd5b [1] > Link: https://github.com/rust-lang/rust-bindgen/pull/2319 [2] > Link: https://github.com/rust-lang/rust-bindgen/pull/1990 [3] > Link: https://github.com/rust-lang/rust-bindgen/issues/2094 [4] > Link: https://github.com/rust-lang/rust-bindgen/commit/cc78b6fdb6e829e5fb8fa1639f2182cb49333569 [5] > Link: https://github.com/rust-lang/rust-bindgen/pull/2408 [6] > Closes: https://github.com/Rust-for-Linux/linux/issues/1013 [7] > Signed-off-by: Aakash Sen Sharma <aakashsensharma@xxxxxxxxx> Applied to `rust-next`, thanks everyone! I also did these extra changes: [ Reworded commit message. Mentioned the `bindgen-cli` binary crate change, linked to it and updated the Quick Start guide. Re-added a deleted "as" word in a code comment and reflowed comment to respect the maximum length. ] In particular, I have reworded the commit message a fair bit: In LLVM 16, anonymous items may return names like `(unnamed union at ..)` rather than empty names [1], which breaks Rust-enabled builds because bindgen assumed an empty name instead of detecting them via `clang_Cursor_isAnonymous` [2]: $ make rustdoc LLVM=1 CLIPPY=1 -j$(nproc) RUSTC L rust/core.o BINDGEN rust/bindings/bindings_generated.rs BINDGEN rust/bindings/bindings_helpers_generated.rs BINDGEN rust/uapi/uapi_generated.rs thread 'main' panicked at '"ftrace_branch_data_union_(anonymous_at__/_/include/linux/compiler_types_h_146_2)" is not a valid Ident', .../proc-macro2-1.0.24/src/fallback.rs:693:9 ... thread 'main' panicked at '"ftrace_branch_data_union_(anonymous_at__/_/include/linux/compiler_types_h_146_2)" is not a valid Ident', .../proc-macro2-1.0.24/src/fallback.rs:693:9 ... This was fixed in bindgen 0.62.0. Therefore, upgrade bindgen to a more recent version, 0.65.1, to support LLVM 16. Since bindgen 0.58.0 changed the `--{white,black}list-*` flags to `--{allow,block}list-*` [3], update them on our side too. In addition, bindgen 0.61.0 moved its CLI utility into a binary crate called `bindgen-cli` [4]. Thus update the installation command in the Quick Start guide. Moreover, bindgen 0.61.0 changed the default functionality to bind `size_t` to `usize` [5] and added the `--no-size_t-is-usize` flag to not bind `size_t` as `usize`. Then bindgen 0.65.0 removed the `--size_t-is-usize` flag [6]. Thus stop passing the flag to bindgen. Finally, bindgen 0.61.0 added support for the `noreturn` attribute (in its different forms) [7]. Thus remove the infinite loop in our Rust panic handler after calling `BUG()`, since bindgen now correctly generates a `BUG()` binding that returns `!` instead of `()`. Link: https://github.com/llvm/llvm-project/commit/19e984ef8f49bc3ccced15621989fa9703b2cd5b [1] Link: https://github.com/rust-lang/rust-bindgen/pull/2319 [2] Link: https://github.com/rust-lang/rust-bindgen/pull/1990 [3] Link: https://github.com/rust-lang/rust-bindgen/pull/2284 [4] Link: https://github.com/rust-lang/rust-bindgen/commit/cc78b6fdb6e829e5fb8fa1639f2182cb49333569 [5] Link: https://github.com/rust-lang/rust-bindgen/pull/2408 [6] Link: https://github.com/rust-lang/rust-bindgen/issues/2094 [7] Aakash: please let me know if that is not OK! Cheers, Miguel
