[clang][ItaniumMangle] Mangle friend function templates with a constr…

[VitaNuo]

…aint that depends on a template parameter from an enclosing template as members of the enclosing class.

Such function templates should be considered member-like constrained friends per [temp.friend]p9 and itanium-cxx-abi/cxx-abi#24 (comment)).

[llvmbot]

@llvm/pr-subscribers-libcxxabi

@llvm/pr-subscribers-clang

Author: Viktoriia Bakalova (VitaNuo)

Changes

…aint that depends on a template parameter from an enclosing template as members of the enclosing class.

Such function templates should be considered member-like constrained friends per [temp.friend]p9 and itanium-cxx-abi/cxx-abi#24 (comment)).

---

Full diff: https://github.com/llvm/llvm-project/pull/110247.diff

3 Files Affected:

• (modified) clang/lib/AST/ItaniumMangle.cpp (+8)
• (modified) clang/test/CodeGenCXX/mangle-concept.cpp (+3-3)
• (modified) libcxxabi/test/test_demangle.pass.cpp (+3-3)

diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index b6e1da0c3192da..172561f73b9a74 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -2270,6 +2270,14 @@ void CXXNameMangler::mangleTemplatePrefix(GlobalDecl GD,
     mangleTemplateParameter(TTP->getDepth(), TTP->getIndex());
   } else {
     const DeclContext *DC = Context.getEffectiveDeclContext(ND);
+    if (const auto *FD = dyn_cast<FunctionTemplateDecl>(GD.getDecl())) {
+      // Member-like constrained friends are mangled as if they were members of
+      // the enclosing class.
+      if (FD->getTemplatedDecl()->isMemberLikeConstrainedFriend() &&
+          getASTContext().getLangOpts().getClangABICompat() >
+              LangOptions::ClangABI::Ver17)
+      DC = GD.getDecl()->getLexicalDeclContext()->getRedeclContext();
+    }
     manglePrefix(DC, NoFunction);
     if (isa<BuiltinTemplateDecl>(ND) || isa<ConceptDecl>(ND))
       mangleUnqualifiedName(GD, DC, nullptr);
diff --git a/clang/test/CodeGenCXX/mangle-concept.cpp b/clang/test/CodeGenCXX/mangle-concept.cpp
index 91dc1b0e688e0d..6053511c00a7b5 100644
--- a/clang/test/CodeGenCXX/mangle-concept.cpp
+++ b/clang/test/CodeGenCXX/mangle-concept.cpp
@@ -58,19 +58,19 @@ namespace test2 {
     // CHECK: call {{.*}}@_ZN5test21AIiEF1fEzQ4TrueIT_E(
     // CLANG17: call {{.*}}@_ZN5test21fEz(
     f(ai);
-    // CHECK: call {{.*}}@_ZN5test2F1gIvEEvzQaa4TrueIT_E4TrueITL0__E(
+    // CHECK: call {{.*}}@_ZN5test21AIiEF1gIvEEvzQaa4TrueIT_E4TrueITL0__E(
     // CLANG17: call {{.*}}@_ZN5test21gIvEEvz(
     g(ai);
     // CHECK: call {{.*}}@_ZN5test21hIvEEvzQ4TrueITL0__E(
     // CLANG17: call {{.*}}@_ZN5test21hIvEEvz(
     h(ai);
-    // CHECK: call {{.*}}@_ZN5test2F1iIvQaa4TrueIT_E4TrueITL0__EEEvz(
+    // CHECK: call {{.*}}@_ZN5test21AIiEF1iIvQaa4TrueIT_E4TrueITL0__EEEvz(
     // CLANG17: call {{.*}}@_ZN5test21iIvEEvz(
     i(ai);
     // CHECK: call {{.*}}@_ZN5test21jIvQ4TrueITL0__EEEvz(
     // CLANG17: call {{.*}}@_ZN5test21jIvEEvz(
     j(ai);
-    // CHECK: call {{.*}}@_ZN5test2F1kITk4TruevQ4TrueIT_EEEvz(
+    // CHECK: call {{.*}}@_ZN5test21AIiEF1kITk4TruevQ4TrueIT_EEEvz(
     // CLANG17: call {{.*}}@_ZN5test21kIvEEvz(
     k(ai);
     // CHECK: call {{.*}}@_ZN5test21lITk4TruevEEvz(
diff --git a/libcxxabi/test/test_demangle.pass.cpp b/libcxxabi/test/test_demangle.pass.cpp
index 17786a3a486fcd..efe482aad1b76c 100644
--- a/libcxxabi/test/test_demangle.pass.cpp
+++ b/libcxxabi/test/test_demangle.pass.cpp
@@ -30128,11 +30128,11 @@ const char* cases[][2] =
     // C++20 concepts, see https://github.com/itanium-cxx-abi/cxx-abi/issues/24.
     {"_Z2f0IiE1SIX1CIT_EEEv", "S<C<int>> f0<int>()"},
     {"_ZN5test21AIiEF1fEzQ4TrueIT_E", "test2::A<int>::friend f(...) requires True<T>"},
-    {"_ZN5test2F1gIvEEvzQaa4TrueIT_E4TrueITL0__E", "void test2::friend g<void>(...) requires True<T> && True<TL0_>"},
+    {"_ZN5test21AIiEF1gIvEEvzQaa4TrueIT_E4TrueITL0__E", "void test2::A<int>::friend g<void>(...) requires True<T> && True<TL0_>"},
     {"_ZN5test21hIvEEvzQ4TrueITL0__E", "void test2::h<void>(...) requires True<TL0_>"},
-    {"_ZN5test2F1iIvQaa4TrueIT_E4TrueITL0__EEEvz", "void test2::friend i<void>(...)"},
+    {"_ZN5test21AIiEF1iIvQaa4TrueIT_E4TrueITL0__EEEvz", "void test2::A<int>::friend i<void>(...)"},
     {"_ZN5test21jIvQ4TrueITL0__EEEvz", "void test2::j<void>(...)"},
-    {"_ZN5test2F1kITk4TruevQ4TrueIT_EEEvz", "void test2::friend k<void>(...)"},
+    {"_ZN5test21AIiEF1kITk4TruevQ4TrueIT_EEEvz", "void test2::A<int>::friend k<void>(...)"},
     {"_ZN5test21lITk4TruevEEvz", "void test2::l<void>(...)"},
     {"_ZN5test31dITnDaLi0EEEvv", "void test3::d<0>()"},
     {"_ZN5test31eITnDcLi0EEEvv", "void test3::e<0>()"},

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[usx95]

Thanks for catching and fixing this.

Please also add release notes in clang/docs/ReleaseNotes.rst

[usx95]

Thanks. LGTM.

Left a comment to simplify the change.

[usx95]

Let's reuse the function decl above.

We could use the Decl::getAsFunction() to do both of these checks for us.

if (const auto *FD = D->getAsFunction())

[VitaNuo]

Great idea!

[zygoloid]

Should this have -fclang-abi-compat support?

[hokein]

Should this have -fclang-abi-compat support?

(It seems like we should, although I don’t have direct experience with it.)

This is a bug fix for 4b163e3, which is released in Clang 18 and Clang 19. Therefore, we should likely add -fclang-abi-compat for Ver19?