Fix CFI: f32 and f64 are encoded incorrectly for c

Fix rust-lang#115150 by encoding f32 and f64 correctly for cross-language CFI. I missed changing the encoding for f32 and f64 when I introduced the integer normalization option in rust-lang#105452 as integer normalization does not include floating point. `f32` and `f64` should be always encoded as `f` and `d` since they are both FFI safe when their representation are the same (i.e., IEEE 754) for both the Rust compiler and Clang.
maurer · Apr 1, 2024 · dba48c9 · dba48c9
1 parent cc66ad4
commit dba48c9
Show file tree

Hide file tree

Showing 2 changed files with 19 additions and 10 deletions.
diff --git a/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs b/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs
@@ -447,7 +447,7 @@ fn encode_ty<'tcx>(
             typeid.push('b');
         }
 
-        ty::Int(..) | ty::Uint(..) | ty::Float(..) => {
+        ty::Int(..) | ty::Uint(..) => {
             // u<length><type-name> as vendor extended type
             let mut s = String::from(match ty.kind() {
                 ty::Int(IntTy::I8) => "u2i8",
@@ -462,14 +462,23 @@ fn encode_ty<'tcx>(
                 ty::Uint(UintTy::U64) => "u3u64",
                 ty::Uint(UintTy::U128) => "u4u128",
                 ty::Uint(UintTy::Usize) => "u5usize",
-                ty::Float(FloatTy::F32) => "u3f32",
-                ty::Float(FloatTy::F64) => "u3f64",
-                _ => "",
+                _ => bug!("encode_ty: unexpected `{:?}`", ty.kind()),
             });
             compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
             typeid.push_str(&s);
         }
 
+        // Rust's f32 and f64 single (32-bit) and double (64-bit) precision floating-point types
+        // have IEEE-754 binary32 and binary64 floating-point layouts, respectively.
+        //
+        // (See https://rust-lang.github.io/unsafe-code-guidelines/layout/scalars.html#fixed-width-floating-point-types.)
+        ty::Float(float_ty) => {
+            typeid.push(match float_ty {
+                FloatTy::F32 => 'f',
+                FloatTy::F64 => 'd',
+            });
+        }
+
         ty::Char => {
             // u4char as vendor extended type
             let mut s = String::from("u4char");

diff --git a/tests/codegen/sanitizer/cfi-emit-type-metadata-id-itanium-cxx-abi.rs b/tests/codegen/sanitizer/cfi-emit-type-metadata-id-itanium-cxx-abi.rs
@@ -500,12 +500,12 @@ pub fn foo149(_: Type14<Bar>, _: Type14<Bar>, _: Type14<Bar>) { }
 // CHECK: ![[TYPE45]] = !{i64 0, !"_ZTSFvu5usizeE"}
 // CHECK: ![[TYPE46]] = !{i64 0, !"_ZTSFvu5usizeS_E"}
 // CHECK: ![[TYPE47]] = !{i64 0, !"_ZTSFvu5usizeS_S_E"}
-// CHECK: ![[TYPE48]] = !{i64 0, !"_ZTSFvu3f32E"}
-// CHECK: ![[TYPE49]] = !{i64 0, !"_ZTSFvu3f32S_E"}
-// CHECK: ![[TYPE50]] = !{i64 0, !"_ZTSFvu3f32S_S_E"}
-// CHECK: ![[TYPE51]] = !{i64 0, !"_ZTSFvu3f64E"}
-// CHECK: ![[TYPE52]] = !{i64 0, !"_ZTSFvu3f64S_E"}
-// CHECK: ![[TYPE53]] = !{i64 0, !"_ZTSFvu3f64S_S_E"}
+// CHECK: ![[TYPE48]] = !{i64 0, !"_ZTSFvfE"}
+// CHECK: ![[TYPE49]] = !{i64 0, !"_ZTSFvffE"}
+// CHECK: ![[TYPE50]] = !{i64 0, !"_ZTSFvfffE"}
+// CHECK: ![[TYPE51]] = !{i64 0, !"_ZTSFvdE"}
+// CHECK: ![[TYPE52]] = !{i64 0, !"_ZTSFvddE"}
+// CHECK: ![[TYPE53]] = !{i64 0, !"_ZTSFvdddE"}
 // CHECK: ![[TYPE54]] = !{i64 0, !"_ZTSFvu4charE"}
 // CHECK: ![[TYPE55]] = !{i64 0, !"_ZTSFvu4charS_E"}
 // CHECK: ![[TYPE56]] = !{i64 0, !"_ZTSFvu4charS_S_E"}