From d2ed8cf6619764e2a0af8a691c4ccb8c034b1e57 Mon Sep 17 00:00:00 2001 From: Kevin Reid Date: Mon, 27 Jan 2025 09:34:56 -0800 Subject: [PATCH] Optionally add type names to `TypeId`s. This feature is intended to provide expensive but thorough help for developers who have an unexpected `TypeId` value and need to determine what type it actually is. It causes `impl Debug for TypeId` to print the type name in addition to the opaque ID hash, and in order to do so, adds a name field to `TypeId`. The cost of this is the increased size of `TypeId` and the need to store type names in the binary; therefore, it is an optional feature. It may be enabled via `cargo -Zbuild-std -Zbuild-std-features=debug_typeid`. (Note that `-Zbuild-std-features` disables default features which you may wish to reenable in addition; see .) Example usage and output: ``` fn main() { use std::any::{Any, TypeId}; dbg!(TypeId::of::(), drop::.type_id()); } ``` ``` TypeId::of::() = TypeId(0x763d199bccd319899208909ed1a860c6 = usize) drop::.type_id() = TypeId(0xe6a34bd13f8c92dd47806da07b8cca9a = core::mem::drop) ``` Also added feature declarations for the existing `debug_refcell` feature so it is usable from the `rust.std-features` option of `config.toml`. --- library/core/Cargo.toml | 2 ++ library/core/src/any.rs | 20 +++++++++++++++++--- library/coretests/tests/any.rs | 8 ++++++++ library/std/Cargo.toml | 7 +++++++ library/sysroot/Cargo.toml | 4 +++- 5 files changed, 37 insertions(+), 4 deletions(-) diff --git a/library/core/Cargo.toml b/library/core/Cargo.toml index b7c6db6c78dde..e49d978a36787 100644 --- a/library/core/Cargo.toml +++ b/library/core/Cargo.toml @@ -23,6 +23,8 @@ optimize_for_size = [] # Make `RefCell` store additional debugging information, which is printed out when # a borrow error occurs debug_refcell = [] +# Make `TypeId` store a reference to the name of the type, so that it can print that name. +debug_typeid = [] [lints.rust.unexpected_cfgs] level = "warn" diff --git a/library/core/src/any.rs b/library/core/src/any.rs index 17d9455592787..3565cb4a3adc1 100644 --- a/library/core/src/any.rs +++ b/library/core/src/any.rs @@ -616,6 +616,8 @@ pub struct TypeId { // We avoid using `u128` because that imposes higher alignment requirements on many platforms. // See issue #115620 for more information. t: (u64, u64), + #[cfg(feature = "debug_typeid")] + name: &'static str, } #[stable(feature = "rust1", since = "1.0.0")] @@ -647,10 +649,14 @@ impl TypeId { #[rustc_const_unstable(feature = "const_type_id", issue = "77125")] pub const fn of() -> TypeId { let t: u128 = intrinsics::type_id::(); - let t1 = (t >> 64) as u64; let t2 = t as u64; - TypeId { t: (t1, t2) } + + TypeId { + t: (t1, t2), + #[cfg(feature = "debug_typeid")] + name: type_name::(), + } } fn as_u128(self) -> u128 { @@ -681,7 +687,15 @@ impl hash::Hash for TypeId { #[stable(feature = "rust1", since = "1.0.0")] impl fmt::Debug for TypeId { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> { - write!(f, "TypeId({:#034x})", self.as_u128()) + #[cfg(feature = "debug_typeid")] + { + write!(f, "TypeId({:#034x} = {})", self.as_u128(), self.name)?; + } + #[cfg(not(feature = "debug_typeid"))] + { + write!(f, "TypeId({:#034x})", self.as_u128())?; + } + Ok(()) } } diff --git a/library/coretests/tests/any.rs b/library/coretests/tests/any.rs index 25002617d0bbd..117ef0042380d 100644 --- a/library/coretests/tests/any.rs +++ b/library/coretests/tests/any.rs @@ -118,6 +118,14 @@ fn any_unsized() { is_any::<[i32]>(); } +#[cfg(feature = "debug_typeid")] +#[test] +fn debug_typeid_includes_name() { + let type_id = TypeId::of::<[usize; 2]>(); + let debug_str = format!("{type_id:?}"); + assert!(debug_str.ends_with("= [usize; 2])"), "{debug_str:?} did not match"); +} + #[test] fn distinct_type_names() { // https://github.com/rust-lang/rust/issues/84666 diff --git a/library/std/Cargo.toml b/library/std/Cargo.toml index 9eab75b06961f..1d964cab087bd 100644 --- a/library/std/Cargo.toml +++ b/library/std/Cargo.toml @@ -109,6 +109,13 @@ panic_immediate_abort = [ # Choose algorithms that are optimized for binary size instead of runtime performance optimize_for_size = ["core/optimize_for_size", "alloc/optimize_for_size"] +# Make `RefCell` store additional debugging information, which is printed out when +# a borrow error occurs +debug_refcell = ["core/debug_refcell"] +# Make `TypeId` store a reference to the name of the type, so that it can print that name. +debug_typeid = ["core/debug_typeid"] + + # Enable std_detect default features for stdarch/crates/std_detect: # https://github.com/rust-lang/stdarch/blob/master/crates/std_detect/Cargo.toml std_detect_file_io = ["std_detect/std_detect_file_io"] diff --git a/library/sysroot/Cargo.toml b/library/sysroot/Cargo.toml index aa6c3dc32e2ba..6ed2756e526d6 100644 --- a/library/sysroot/Cargo.toml +++ b/library/sysroot/Cargo.toml @@ -19,11 +19,13 @@ compiler-builtins-mem = ["std/compiler-builtins-mem"] compiler-builtins-no-asm = ["std/compiler-builtins-no-asm"] compiler-builtins-no-f16-f128 = ["std/compiler-builtins-no-f16-f128"] compiler-builtins-mangled-names = ["std/compiler-builtins-mangled-names"] +debug_refcell = ["std/debug_refcell"] +debug_typeid = ["std/debug_typeid"] llvm-libunwind = ["std/llvm-libunwind"] system-llvm-libunwind = ["std/system-llvm-libunwind"] +optimize_for_size = ["std/optimize_for_size"] panic-unwind = ["std/panic_unwind"] panic_immediate_abort = ["std/panic_immediate_abort"] -optimize_for_size = ["std/optimize_for_size"] profiler = ["dep:profiler_builtins"] std_detect_file_io = ["std/std_detect_file_io"] std_detect_dlsym_getauxval = ["std/std_detect_dlsym_getauxval"]