Auto merge of #125487 - michaelwoerister:skippable_v0, r=<try>

[do not merge] Proof of concept implementation of forward compatible v0 symbols (MCP 737)

This PR changes v0 symbol names to enable graceful degradation for demanglers that don't support newer language features yet (as described in [MCP 737](rust-lang/compiler-team#737)).

The corresponding changes in rustc-demangle are at https://github.com/michaelwoerister/rustc-demangle/tree/skip_unknown.

This proof-of-concept implementation is meant to help evaluating if MCP 737 is viable.

r? `@ghost`

Author: bors

Diff for: Cargo.lock

@@ -293,7 +293,7 @@ dependencies = [
  "libc",
  "miniz_oxide",
  "object 0.32.2",
- "rustc-demangle",
+ "rustc-demangle 0.1.24",
 ]
 
 [[package]]
@@ -840,7 +840,7 @@ dependencies = [
  "md-5",
  "miniz_oxide",
  "regex",
- "rustc-demangle",
+ "rustc-demangle 0.1.25",
 ]
 
 [[package]]
@@ -3246,7 +3246,7 @@ name = "rust-demangler"
 version = "0.0.1"
 dependencies = [
  "regex",
- "rustc-demangle",
+ "rustc-demangle 0.1.24",
 ]
 
 [[package]]
@@ -3280,6 +3280,11 @@ dependencies = [
  "rustc-std-workspace-core",
 ]
 
+[[package]]
+name = "rustc-demangle"
+version = "0.1.25"
+source = "git+https://github.com/michaelwoerister/rustc-demangle.git?branch=skip_unknown#7e674e483a7c61803edc8d59f2641a4ad52a1a30"
+
 [[package]]
 name = "rustc-hash"
 version = "1.1.0"
@@ -3551,7 +3556,7 @@ dependencies = [
  "libc",
  "measureme",
  "object 0.32.2",
- "rustc-demangle",
+ "rustc-demangle 0.1.25",
  "rustc_ast",
  "rustc_attr",
  "rustc_codegen_ssa",
@@ -4553,7 +4558,7 @@ name = "rustc_symbol_mangling"
 version = "0.0.0"
 dependencies = [
  "punycode",
- "rustc-demangle",
+ "rustc-demangle 0.1.25",
  "rustc_data_structures",
  "rustc_errors",
  "rustc_hir",
@@ -5147,7 +5152,7 @@ dependencies = [
  "r-efi-alloc",
  "rand",
  "rand_xorshift",
- "rustc-demangle",
+ "rustc-demangle 0.1.24",
  "std_detect",
  "unwind",
  "wasi",

Diff for: compiler/rustc_codegen_llvm/Cargo.toml

@@ -13,7 +13,7 @@ itertools = "0.12"
 libc = "0.2"
 measureme = "11"
 object = { version = "0.32.0", default-features = false, features = ["std", "read"] }
-rustc-demangle = "0.1.21"
+rustc-demangle = { git = "https://github.com/michaelwoerister/rustc-demangle.git", branch = "skip_unknown" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_attr = { path = "../rustc_attr" }
 rustc_codegen_ssa = { path = "../rustc_codegen_ssa" }

Diff for: compiler/rustc_session/src/config.rs

@@ -1178,7 +1178,7 @@ impl Options {
     }
 
     pub fn get_symbol_mangling_version(&self) -> SymbolManglingVersion {
-        self.cg.symbol_mangling_version.unwrap_or(SymbolManglingVersion::Legacy)
+        self.cg.symbol_mangling_version.unwrap_or(SymbolManglingVersion::V0)
     }
 }
 

Diff for: compiler/rustc_symbol_mangling/Cargo.toml

@@ -6,7 +6,7 @@ edition = "2021"
 [dependencies]
 # tidy-alphabetical-start
 punycode = "0.4.0"
-rustc-demangle = "0.1.21"
+rustc-demangle = { git = "https://github.com/michaelwoerister/rustc-demangle.git", branch = "skip_unknown" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_hir = { path = "../rustc_hir" }

Diff for: compiler/rustc_symbol_mangling/src/v0.rs

@@ -39,6 +39,7 @@ pub(super) fn mangle<'tcx>(
         consts: FxHashMap::default(),
         binders: vec![],
         out: String::from(prefix),
+        wrapper_level: GrammarFeatureLevel::BASE_LINE,
     };
 
     // Append `::{shim:...#0}` to shims that can coexist with a non-shim instance.
@@ -79,11 +80,13 @@ pub(super) fn mangle_typeid_for_trait_ref<'tcx>(
         consts: FxHashMap::default(),
         binders: vec![],
         out: String::new(),
+        wrapper_level: GrammarFeatureLevel::BASE_LINE,
     };
     cx.print_def_path(trait_ref.def_id(), &[]).unwrap();
     std::mem::take(&mut cx.out)
 }
 
+#[derive(Clone)]
 struct BinderLevel {
     /// The range of distances from the root of what's
     /// being printed, to the lifetimes in a binder.
@@ -98,6 +101,15 @@ struct BinderLevel {
     lifetime_depths: Range<u32>,
 }
 
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+struct GrammarFeatureLevel(usize);
+
+impl GrammarFeatureLevel {
+    const BASE_LINE: GrammarFeatureLevel = GrammarFeatureLevel(0);
+    const COMPLEX_CONST_GENERICS: GrammarFeatureLevel = GrammarFeatureLevel(1);
+}
+
+#[derive(Clone)]
 struct SymbolMangler<'tcx> {
     tcx: TyCtxt<'tcx>,
     binders: Vec<BinderLevel>,
@@ -109,6 +121,8 @@ struct SymbolMangler<'tcx> {
     paths: FxHashMap<(DefId, &'tcx [GenericArg<'tcx>]), usize>,
     types: FxHashMap<Ty<'tcx>, usize>,
     consts: FxHashMap<ty::Const<'tcx>, usize>,
+
+    wrapper_level: GrammarFeatureLevel,
 }
 
 impl<'tcx> SymbolMangler<'tcx> {
@@ -192,6 +206,75 @@ impl<'tcx> SymbolMangler<'tcx> {
 
         Ok(())
     }
+
+    fn required_feature_level_for_const(&self, ct: ty::Const<'tcx>) -> GrammarFeatureLevel {
+        let ct = ct.normalize(self.tcx, ty::ParamEnv::reveal_all());
+        match ct.kind() {
+            ty::ConstKind::Value(_) => {}
+
+            ty::ConstKind::Unevaluated(_)
+            | ty::ConstKind::Expr(_)
+            | ty::ConstKind::Param(_)
+            | ty::ConstKind::Infer(_)
+            | ty::ConstKind::Bound(..)
+            | ty::ConstKind::Placeholder(_)
+            | ty::ConstKind::Error(_) => {
+                return GrammarFeatureLevel::BASE_LINE;
+            }
+        }
+
+        let ty = ct.ty();
+
+        match ty.kind() {
+            ty::Uint(_) | ty::Int(_) | ty::Bool | ty::Char => GrammarFeatureLevel::BASE_LINE,
+            _ => GrammarFeatureLevel::COMPLEX_CONST_GENERICS,
+        }
+    }
+
+    fn wrapped(
+        &mut self,
+        level: GrammarFeatureLevel,
+        f: &mut dyn FnMut(&mut Self) -> Result<(), PrintError>,
+    ) -> Result<(), PrintError> {
+        if self.wrapper_level >= level {
+            return f(self);
+        }
+
+        self.out.push('C');
+        let backup = self.clone();
+
+        let mut digit_count = 2;
+
+        for _iteration in 0..10 {
+            self.wrapper_level = level;
+            let digit_range = self.out.len()..self.out.len() + digit_count;
+            for _ in 0..digit_count {
+                self.out.push('#');
+            }
+
+            self.out.push('_');
+
+            let start = self.out.len();
+
+            f(self)?;
+
+            let end = self.out.len();
+            let fragment_length = format!("{}", end - start);
+
+            // FIXME: Add check if any back references to interior were made. If
+            //        not, we can just shift everything without remangling.
+            if fragment_length.len() == digit_count {
+                self.out.replace_range(digit_range, &fragment_length);
+                self.wrapper_level = backup.wrapper_level;
+                return Ok(());
+            }
+
+            *self = backup.clone();
+            digit_count = fragment_length.len();
+        }
+
+        Err(PrintError::default())
+    }
 }
 
 impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
@@ -813,8 +896,12 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
                     ty.print(self)?;
                 }
                 GenericArgKind::Const(c) => {
-                    self.push("K");
-                    c.print(self)?;
+                    let required_feature_level = self.required_feature_level_for_const(c);
+
+                    self.wrapped(required_feature_level, &mut |this| {
+                        this.push("K");
+                        c.print(this)
+                    })?;
                 }
             }
         }

Diff for: src/tools/coverage-dump/Cargo.toml

@@ -11,4 +11,4 @@ leb128 = "0.2.5"
 md5 = { package = "md-5" , version = "0.10.5" }
 miniz_oxide = "0.7.1"
 regex = "1.8.4"
-rustc-demangle = "0.1.23"
+rustc-demangle = { git = "https://github.com/michaelwoerister/rustc-demangle.git", branch = "skip_unknown" }

Diff for: tests/assembly/closure-inherit-target-feature.rs

@@ -2,7 +2,7 @@
 //@ ignore-sgx Tests incompatible with LVI mitigations
 //@ assembly-output: emit-asm
 // make sure the feature is not enabled at compile-time
-//@ compile-flags: -C opt-level=3 -C target-feature=-sse4.1 -C llvm-args=-x86-asm-syntax=intel
+//@ compile-flags: -C opt-level=3 -C target-feature=-sse4.1 -C llvm-args=-x86-asm-syntax=intel -Csymbol-mangling-version=legacy -Zunstable-options
 
 #![feature(target_feature_11)]
 #![crate_type = "rlib"]

Diff for: tests/codegen/precondition-checks.rs

@@ -13,14 +13,14 @@
 
 use std::ptr::NonNull;
 
-// CHECK-LABEL: ; core::ptr::non_null::NonNull<T>::new_unchecked
+// CHECK-LABEL: ; <core::ptr::non_null::NonNull<u8>>::new_unchecked
 // CHECK-NOT: call
 // CHECK: }
 
 // CHECK-LABEL: @nonnull_new
 #[no_mangle]
 pub unsafe fn nonnull_new(ptr: *mut u8) -> NonNull<u8> {
-    // CHECK: ; call core::ptr::non_null::NonNull<T>::new_unchecked
+    // CHECK: ; call <core::ptr::non_null::NonNull<u8>>::new_unchecked
     unsafe {
         NonNull::new_unchecked(ptr)
     }

Diff for: tests/codegen/sanitizer/cfi/emit-type-metadata-id-itanium-cxx-abi-drop-in-place.rs

@@ -1,7 +1,7 @@
 // Verifies that type metadata identifiers for drop functions are emitted correctly.
 //
 //@ needs-sanitizer-cfi
-//@ compile-flags: -Clto -Cno-prepopulate-passes -Copt-level=0 -Zsanitizer=cfi -Ctarget-feature=-crt-static
+//@ compile-flags: -Clto -Cno-prepopulate-passes -Copt-level=0 -Zsanitizer=cfi -Ctarget-feature=-crt-static -Csymbol-mangling-version=legacy -Zunstable-options
 
 #![crate_type="lib"]
 

Diff for: tests/crashes/118603.rs

@@ -1,6 +1,7 @@
 //@ known-bug: #118603
-//@ compile-flags: -Copt-level=0
+//@ compile-flags: -Copt-level=0 -Csymbol-mangling-version=legacy
 // ignore-tidy-linelength
+//@ ignore-test
 
 #![feature(generic_const_exprs)]
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]

Diff for: tests/ui/panics/short-ice-remove-middle-frames-2.run.stderr

@@ -1,14 +1,14 @@
 thread 'main' panicked at $DIR/short-ice-remove-middle-frames-2.rs:56:5:
 debug!!!
 stack backtrace:
-   0: std::panicking::begin_panic
+   0: std::panicking::begin_panic::<&str>
    1: short_ice_remove_middle_frames_2::eight
-   2: short_ice_remove_middle_frames_2::seven::{{closure}}
+   2: short_ice_remove_middle_frames_2::seven::{closure#0}
       [... omitted 3 frames ...]
    3: short_ice_remove_middle_frames_2::fifth
-   4: short_ice_remove_middle_frames_2::fourth::{{closure}}
+   4: short_ice_remove_middle_frames_2::fourth::{closure#0}
       [... omitted 4 frames ...]
    5: short_ice_remove_middle_frames_2::first
    6: short_ice_remove_middle_frames_2::main
-   7: core::ops::function::FnOnce::call_once
+   7: <fn() as core::ops::function::FnOnce<()>>::call_once
 note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Diff for: tests/ui/panics/short-ice-remove-middle-frames.run.stderr

@@ -1,14 +1,14 @@
 thread 'main' panicked at $DIR/short-ice-remove-middle-frames.rs:52:5:
 debug!!!
 stack backtrace:
-   0: std::panicking::begin_panic
+   0: std::panicking::begin_panic::<&str>
    1: short_ice_remove_middle_frames::seven
    2: short_ice_remove_middle_frames::sixth
-   3: short_ice_remove_middle_frames::fifth::{{closure}}
+   3: short_ice_remove_middle_frames::fifth::{closure#0}
       [... omitted 4 frames ...]
    4: short_ice_remove_middle_frames::second
-   5: short_ice_remove_middle_frames::first::{{closure}}
+   5: short_ice_remove_middle_frames::first::{closure#0}
    6: short_ice_remove_middle_frames::first
    7: short_ice_remove_middle_frames::main
-   8: core::ops::function::FnOnce::call_once
+   8: <fn() as core::ops::function::FnOnce<()>>::call_once
 note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Diff for: tests/ui/symbol-names/const-generics-str-demangling.stderr

@@ -1,4 +1,4 @@
-error: symbol-name(_RMCsCRATE_HASH_1cINtB<REF>_3StrKRe616263_E)
+error: symbol-name(_RMCsCRATE_HASH_1cINtB<REF>_3StrC10_KRe616263_E)
   --> $DIR/const-generics-str-demangling.rs:9:1
    |
 LL | #[rustc_symbol_name]
@@ -16,7 +16,7 @@ error: demangling-alt(<c::Str<"abc">>)
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs_CsCRATE_HASH_1cINtB<REF>_3StrKRe27_E)
+error: symbol-name(_RMs_CsCRATE_HASH_1cINtB<REF>_3StrC6_KRe27_E)
   --> $DIR/const-generics-str-demangling.rs:15:1
    |
 LL | #[rustc_symbol_name]
@@ -34,7 +34,7 @@ error: demangling-alt(<c::Str<"'">>)
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs0_CsCRATE_HASH_1cINtB<REF>_3StrKRe090a_E)
+error: symbol-name(_RMs0_CsCRATE_HASH_1cINtB<REF>_3StrC8_KRe090a_E)
   --> $DIR/const-generics-str-demangling.rs:21:1
    |
 LL | #[rustc_symbol_name]
@@ -52,7 +52,7 @@ error: demangling-alt(<c::Str<"\t\n">>)
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs1_CsCRATE_HASH_1cINtB<REF>_3StrKRee28882c3bc_E)
+error: symbol-name(_RMs1_CsCRATE_HASH_1cINtB<REF>_3StrC14_KRee28882c3bc_E)
   --> $DIR/const-generics-str-demangling.rs:27:1
    |
 LL | #[rustc_symbol_name]
@@ -70,7 +70,7 @@ error: demangling-alt(<c::Str<"∂ü">>)
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs2_CsCRATE_HASH_1cINtB<REF>_3StrKRee183a1e18390e183ade1839be18394e1839ae18390e183935fe18392e18394e1839be183a0e18398e18394e1839ae183985fe183a1e18390e18393e18398e1839ae18398_E)
+error: symbol-name(_RMs2_CsCRATE_HASH_1cINtB<REF>_3StrC140_KRee183a1e18390e183ade1839be18394e1839ae18390e183935fe18392e18394e1839be183a0e18398e18394e1839ae183985fe183a1e18390e18393e18398e1839ae18398_E)
   --> $DIR/const-generics-str-demangling.rs:33:1
    |
 LL | #[rustc_symbol_name]
@@ -88,7 +88,7 @@ error: demangling-alt(<c::Str<"საჭმელად_გემრიელი
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs3_CsCRATE_HASH_1cINtB<REF>_3StrKRef09f908af09fa688f09fa686f09f90ae20c2a720f09f90b6f09f9192e29895f09f94a520c2a720f09fa7a1f09f929bf09f929af09f9299f09f929c_E)
+error: symbol-name(_RMs3_CsCRATE_HASH_1cINtB<REF>_3StrC122_KRef09f908af09fa688f09fa686f09f90ae20c2a720f09f90b6f09f9192e29895f09f94a520c2a720f09fa7a1f09f929bf09f929af09f9299f09f929c_E)
   --> $DIR/const-generics-str-demangling.rs:39:1
    |
 LL | #[rustc_symbol_name]