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Fix mangling collision for C++ class template specializations (#7269)

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Carbon-side thunks (for example the `Copy`/`Destroy` witness thunks
generated for imported C++ types) are mangled by Carbon, and their names
incorporate a fingerprint of the involved types. The instruction
fingerprinter identifies a class only by its name and parent scope,
which is sufficient for Carbon classes but not for imported C++ classes:
different specializations of one class template (and other cases such as
types in anonymous namespaces) share a Carbon name and parent scope. As
a result, the thunks for two distinct specializations could mangle to
the same name, producing a single LLVM function with two definitions and
failing `verifyModule` during lowering.

When fingerprinting a class imported from C++, also include the Clang
mangled name of its type.

Test: toolchain/lower/testdata/interop/cpp/thunks.carbon gains a split
with two specializations of one class template, each requiring a thunk;
their thunks now get distinct mangled names instead of colliding.

Assisted-by: Claude Code

---------

Co-authored-by: Christopher Di Bella <cjdb.ns@gmail.com>
This commit is contained in:
Chandler Carruth
2026-05-30 08:13:00 +00:00
committed by GitHub
co-authored by Christopher Di Bella
parent 3ef128ac91
commit 8a59f2a76b
64 changed files with 4762 additions and 4330 deletions
Download Patch File Download Diff File Expand all files Collapse all files
toolchain/lower/testdata/interop/cpp/class/import/dynamic.carbon
Vendored
+2 -2
View File
@@ -171,7 +171,7 @@ auto DoThing() -> void {
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define weak_odr void @"_COp.9262bcc12ced4e1e:core.Destroy.Core"(ptr %self) #5 !dbg !33 {
// CHECK:STDOUT: define weak_odr void @"_COp.47e6e98bb48502be:core.Destroy.Core"(ptr %self) #5 !dbg !33 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: ret void, !dbg !36
// CHECK:STDOUT: }
@@ -297,7 +297,7 @@ auto DoThing() -> void {
// CHECK:STDOUT: !30 = !{!31}
// CHECK:STDOUT: !31 = !DILocalVariable(arg: 1, scope: !29, type: !21)
// CHECK:STDOUT: !32 = !DILocation(line: 22, column: 1, scope: !29)
// CHECK:STDOUT: !33 = distinct !DISubprogram(name: "Op", linkageName: "_COp.9262bcc12ced4e1e:core.Destroy.Core", scope: null, file: !6, line: 22, type: !19, spFlags: DISPFlagDefinition, unit: !5, retainedNodes: !34)
// CHECK:STDOUT: !33 = distinct !DISubprogram(name: "Op", linkageName: "_COp.47e6e98bb48502be:core.Destroy.Core", scope: null, file: !6, line: 22, type: !19, spFlags: DISPFlagDefinition, unit: !5, retainedNodes: !34)
// CHECK:STDOUT: !34 = !{!35}
// CHECK:STDOUT: !35 = !DILocalVariable(arg: 1, scope: !33, type: !21)
// CHECK:STDOUT: !36 = !DILocation(line: 22, column: 1, scope: !33)
toolchain/lower/testdata/interop/cpp/class/virtual_fn.carbon
Vendored
+2 -2
View File
@@ -209,7 +209,7 @@ void delete_new_Base() {
// CHECK:STDOUT: declare void @_ZN1AD1Ev(ptr noundef nonnull align 8 dead_on_return(8) dereferenceable(8)) unnamed_addr #7
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define weak_odr void @"_COp.bce205344e07c31d:core.Destroy.Core"(ptr %self) #8 !dbg !29 {
// CHECK:STDOUT: define weak_odr void @"_COp.6a9ecc3bdf183bcf:core.Destroy.Core"(ptr %self) #8 !dbg !29 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: ret void, !dbg !32
// CHECK:STDOUT: }
@@ -380,7 +380,7 @@ void delete_new_Base() {
// CHECK:STDOUT: !26 = !{!27}
// CHECK:STDOUT: !27 = !DILocalVariable(arg: 1, scope: !22, type: !25)
// CHECK:STDOUT: !28 = !DILocation(line: 12, column: 1, scope: !22)
// CHECK:STDOUT: !29 = distinct !DISubprogram(name: "Op", linkageName: "_COp.bce205344e07c31d:core.Destroy.Core", scope: null, file: !6, line: 12, type: !23, spFlags: DISPFlagDefinition, unit: !5, retainedNodes: !30)
// CHECK:STDOUT: !29 = distinct !DISubprogram(name: "Op", linkageName: "_COp.6a9ecc3bdf183bcf:core.Destroy.Core", scope: null, file: !6, line: 12, type: !23, spFlags: DISPFlagDefinition, unit: !5, retainedNodes: !30)
// CHECK:STDOUT: !30 = !{!31}
// CHECK:STDOUT: !31 = !DILocalVariable(arg: 1, scope: !29, type: !25)
// CHECK:STDOUT: !32 = !DILocation(line: 12, column: 1, scope: !29)