Walnut356 · Sep 21, 2026
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
@@ -6,6 +6,7 @@ use std::{assert_matches, iter, ptr};
 
 use libc::{c_longlong, c_uint};
 use rustc_abi::{Align, Endian, Layout, NumScalableVectors, Size};
+use rustc_ast::{IntTy, UintTy};
 use rustc_codegen_ssa::debuginfo::type_names::{VTableNameKind, cpp_like_debuginfo};
 use rustc_codegen_ssa::traits::*;
 use rustc_hir::def::{CtorKind, DefKind};
@@ -795,9 +796,50 @@ fn build_basic_type_di_node<'ll, 'tcx>(
         _ => bug!("debuginfo::build_basic_type_di_node - `t` is invalid type"),
     };
 
-    let ty_di_node = create_basic_type(cx, name, cx.size_of(t), encoding);
+    // Around LLDB 21 or 22, LLDB started using prebuilt Clang type nodes for primitives rather than
+    // reading the full DWARF data. These nodes are based on the size and signedness of the
+    // primitive, and ignore pretty much all other fields. This causes 2 issues:
+    // 1. type names get normalized to C-style names which isn't ideal. The normalization occurs
+    // even in generic args.
+    // 2. if you have a generic type `S<T>`, and 2 instantiations are `S<u64>`
+    // and `S<usize>` (on a 64-bit target), the use of prebuilt nodes causes a name collision.
+    // Whichever instantiation is interacted with first will work fine, all others will break a
+    // bunch of stuff in the LLDB pipeline. To avoid this, we explicitly treat `usize` and `isize`
+    // as typedefs of their equivalent types. For more info see: llvm/llvm-project#196812
+
+    let mut needs_typedef = cpp_like_debuginfo;
+
+    let ty_di_node = match t.kind() {
+        ty::Uint(UintTy::Usize) => {
+            needs_typedef = true;
+
+            let equivalent = match t.primitive_size(cx.tcx).bits() {
+                8 => cx.tcx.types.u8,
+                16 => cx.tcx.types.u16,
+                32 => cx.tcx.types.u32,
+                64 => cx.tcx.types.u64,
+                128 => cx.tcx.types.u128,
+                x => bug!("Unexpected signed int size {x}"),
+            };
+            type_di_node(cx, equivalent)
+        }
+        ty::Int(IntTy::Isize) => {
+            needs_typedef = true;
+
+            let equivalent = match t.primitive_size(cx.tcx).bits() {
+                8 => cx.tcx.types.i8,
+                16 => cx.tcx.types.i16,
+                32 => cx.tcx.types.i32,
+                64 => cx.tcx.types.i64,
+                128 => cx.tcx.types.i128,
+                x => bug!("Unexpected signed int size: {x}"),
+            };
+            type_di_node(cx, equivalent)
+        }
+        _ => create_basic_type(cx, name, cx.size_of(t), encoding),
+    };
 
-    if !cpp_like_debuginfo {
+    if !needs_typedef {
         return DINodeCreationResult::new(ty_di_node, false);
     }
 

diff --git a/tests/debuginfo/basic-types/lldb_input/non_windows.json b/tests/debuginfo/basic-types/lldb_input/non_windows.json
@@ -12,7 +12,7 @@
     "value": false
    },
    "i": {
-    "type": "long",
+    "type": "isize",
     "pretty_print": "-1",
     "value": -1
    },
@@ -43,7 +43,7 @@
     "value": -64
    },
    "u": {
-    "type": "unsigned long",
+    "type": "usize",
     "pretty_print": "1",
     "value": 1
    },

diff --git a/tests/debuginfo/basic-types/lldb_input/windows_gnu.json b/tests/debuginfo/basic-types/lldb_input/windows_gnu.json
@@ -1,7 +1,7 @@
 {
  "bless_metadata": {
   "python_version": "3.11.9 (tags/v3.11.9:de54cf5, Apr  2 2024, 10:12:12) [MSC v.1938 64 bit (AMD64)]",
-  "debugger_version": "lldb version 22.1.2 (https://github.com/llvm/llvm-project revision 1ab49a973e210e97d61e5db6557180dcb92c3e98)\n  clang revision 1ab49a973e210e97d61e5db6557180dcb92c3e98\n  llvm revision 1ab49a973e210e97d61e5db6557180dcb92c3e98",
+  "debugger_version": "lldb version 22.1.8 (https://github.com/llvm/llvm-project revision ca7933e47d3a3451d81e72ac174dcb5aa28b59d1)\n  clang revision ca7933e47d3a3451d81e72ac174dcb5aa28b59d1\n  llvm revision ca7933e47d3a3451d81e72ac174dcb5aa28b59d1",
   "feature_flags": "LLDBFeature.StaticFields|TypeRecognizers|Float128"
  },
  "breakpoints": [
@@ -12,7 +12,7 @@
     "value": false
    },
    "i": {
-    "type": "long long",
+    "type": "isize",
     "pretty_print": "-1",
     "value": -1
    },
@@ -43,7 +43,7 @@
     "value": -64
    },
    "u": {
-    "type": "unsigned long long",
+    "type": "usize",
     "pretty_print": "1",
     "value": 1
    },

diff --git a/tests/debuginfo/pretty-std/lldb_input/non_windows.json b/tests/debuginfo/pretty-std/lldb_input/non_windows.json
@@ -162,7 +162,7 @@
     },
     {
      "name": "length",
-     "type": "unsigned long",
+     "type": "usize",
      "offset": 8
     }
    ]
@@ -171,9 +171,9 @@
    "size": 8,
    "type_class": 4096
   },
-  "unsigned long": {
+  "usize": {
    "size": 8,
-   "type_class": 4,
+   "type_class": 32768,
    "basic_type": 16
   },
   "int": {
@@ -192,7 +192,7 @@
     },
     {
      "name": "len",
-     "type": "unsigned long",
+     "type": "usize",
      "offset": 16
     }
    ],
@@ -281,7 +281,7 @@
    "fields": [
     {
      "name": "__0",
-     "type": "unsigned long",
+     "type": "usize",
      "offset": 0
     }
    ]
@@ -297,6 +297,11 @@
     "unsigned long"
    ]
   },
+  "unsigned long": {
+   "size": 8,
+   "type_class": 4,
+   "basic_type": 16
+  },
   "&str": {
    "size": 16,
    "type_class": 16384,
@@ -308,7 +313,7 @@
     },
     {
      "name": "length",
-     "type": "unsigned long",
+     "type": "usize",
      "offset": 8
     }
    ]
@@ -335,7 +340,7 @@
     },
     {
      "name": "len",
-     "type": "unsigned long",
+     "type": "usize",
      "offset": 16
     }
    ],

diff --git a/tests/debuginfo/pretty-std/lldb_input/windows_gnu.json b/tests/debuginfo/pretty-std/lldb_input/windows_gnu.json
@@ -1,7 +1,7 @@
 {
  "bless_metadata": {
   "python_version": "3.11.9 (tags/v3.11.9:de54cf5, Apr  2 2024, 10:12:12) [MSC v.1938 64 bit (AMD64)]",
-  "debugger_version": "lldb version 22.1.2 (https://github.com/llvm/llvm-project revision 1ab49a973e210e97d61e5db6557180dcb92c3e98)\n  clang revision 1ab49a973e210e97d61e5db6557180dcb92c3e98\n  llvm revision 1ab49a973e210e97d61e5db6557180dcb92c3e98",
+  "debugger_version": "lldb version 22.1.8 (https://github.com/llvm/llvm-project revision ca7933e47d3a3451d81e72ac174dcb5aa28b59d1)\n  clang revision ca7933e47d3a3451d81e72ac174dcb5aa28b59d1\n  llvm revision ca7933e47d3a3451d81e72ac174dcb5aa28b59d1",
   "feature_flags": "LLDBFeature.StaticFields|TypeRecognizers|Float128"
  },
  "breakpoints": [
@@ -173,7 +173,7 @@
     },
     {
      "name": "length",
-     "type": "unsigned long long",
+     "type": "usize",
      "offset": 8
     }
    ]
@@ -182,9 +182,9 @@
    "size": 8,
    "type_class": 4096
   },
-  "unsigned long long": {
+  "usize": {
    "size": 8,
-   "type_class": 4,
+   "type_class": 32768,
    "basic_type": 18
   },
   "int": {
@@ -203,7 +203,7 @@
     },
     {
      "name": "len",
-     "type": "unsigned long long",
+     "type": "usize",
      "offset": 16
     }
    ],
@@ -292,7 +292,7 @@
    "fields": [
     {
      "name": "__0",
-     "type": "unsigned long long",
+     "type": "usize",
      "offset": 0
     }
    ]
@@ -308,6 +308,11 @@
     "unsigned long long"
    ]
   },
+  "unsigned long long": {
+   "size": 8,
+   "type_class": 4,
+   "basic_type": 18
+  },
   "&str": {
    "size": 16,
    "type_class": 16384,
@@ -319,7 +324,7 @@
     },
     {
      "name": "length",
-     "type": "unsigned long long",
+     "type": "usize",
      "offset": 8
     }
    ]
@@ -346,7 +351,7 @@
     },
     {
      "name": "len",
-     "type": "unsigned long long",
+     "type": "usize",
      "offset": 16
     }
    ],

diff --git a/tests/debuginfo/rc_arc.rs b/tests/debuginfo/rc_arc.rs
@@ -21,6 +21,11 @@
 //@ lldb-check:[...] strong=11, weak=2 { value = 111 }
 //@ lldb-command:v arc
 //@ lldb-check:[...] strong=21, weak=2 { data = 222 }
+//@ lldb-command:continue
+//@ lldb-command:v rc_u64
+//@ lldb-check:[...] rc_u64 = strong=1, weak=1 { value = 10 }
+//@ lldb-command:v rc_usize
+//@ lldb-check:[...] rc_usize = strong=1, weak=1 { value = 20 }
 
 // === CDB TESTS ==================================================================================
 
@@ -132,6 +137,11 @@ fn main() {
     let slice_arc_weak = Arc::downgrade(&slice_arc);
 
     zzz(); // #break
+
+    let rc_u64 = Rc::new(10u64);
+    let rc_usize = Rc::new(20usize);
+
+    zzz(); // #break
 }
 
 fn inc_ref_count<T: Clone>(rc: &T, count: usize) {