https://gcc.gnu.org/g:fac66e827216a5593fdf501929babf01338a4e79
commit r16-9512-gfac66e827216a5593fdf501929babf01338a4e79 Author: Jakub Jelinek <[email protected]> Date: Thu Aug 6 13:24:08 2026 +0200 c++: Fix mangling of empty anon union/struct unnamed NSDMs [PR125541] Non-static data members are currently mangled as dm <prefix> <unqualified-name> This works fine for NSDMs with a name, or even the unnamed anon union/struct NSDMs iff they have any named members in them (in that case the <unqualified-name> is using anon_aggr_naming_decl). As the following testcases show, if the anon union/struct is empty, we ICE, because there is nothing we can print as the name. The following patch mangles it similarly to unnamed bitfields in that case, simply counts the index of such problematic empty unnamed anon union/struct within the class and emits _ for the first one, etc. 2026-06-12 Jakub Jelinek <[email protected]> PR c++/125541 * mangle.cc (write_reflection): Mangle empty anonymous union/struct data members as "da" rather than "dm" and use index of such a data member instead of name. * g++.dg/reflect/mangle1.C: Add further 2 tests. * g++.dg/reflect/mangle9.C: New test. Reviewed-by: Jason Merrill <[email protected]> (cherry picked from commit 24754ac2629968fba1681ba51a96ed5bfd51546f) Diff: --- gcc/cp/mangle.cc | 22 ++++++++++++++++++++++ gcc/testsuite/g++.dg/reflect/mangle1.C | 5 +++++ gcc/testsuite/g++.dg/reflect/mangle9.C | 31 +++++++++++++++++++++++++++++++ 3 files changed, 58 insertions(+) diff --git a/gcc/cp/mangle.cc b/gcc/cp/mangle.cc index d8a70233beab..6da1484affa9 100644 --- a/gcc/cp/mangle.cc +++ b/gcc/cp/mangle.cc @@ -4186,6 +4186,8 @@ write_expression (tree expr) [ <alias template-args> ] _ <type> # type alias ::= ty <type> # type ::= dm <prefix> <unqualified-name> # ns data member + ::= da <prefix> [ <nonnegative number> ] _ # empty anon union + # data member ::= un <prefix> [ <nonnegative number> ] _ # unnamed bitfld ::= ct [ <prefix> ] <unqualified-name> # class template ::= ft [ <prefix> ] <unqualified-name> # function template @@ -4207,6 +4209,11 @@ write_reflection (tree refl) { char prefix[3]; tree arg = reflection_mangle_prefix (refl, prefix); + if (strcmp (prefix, "dm") == 0 + && DECL_NAME (arg) == NULL_TREE + && ANON_AGGR_TYPE_P (TREE_TYPE (arg)) + && anon_aggr_naming_decl (TREE_TYPE (arg)) == NULL_TREE) + strcpy (prefix, "da"); write_string (prefix); /* If there is no argument, nothing further needs to be mangled. */ if (arg == NULL_TREE) @@ -4259,6 +4266,21 @@ write_reflection (tree refl) write_prefix (ctx); write_unqualified_name (arg); } + else if (strcmp (prefix, "da") == 0) + { + int idx = 0; + tree ctx = decl_mangling_context (arg); + for (tree f = TYPE_FIELDS (ctx); f; f = DECL_CHAIN (f)) + if (f == arg) + break; + else if (TREE_CODE (f) == FIELD_DECL + && DECL_NAME (f) == NULL_TREE + && ANON_AGGR_TYPE_P (TREE_TYPE (f)) + && anon_aggr_naming_decl (TREE_TYPE (f)) == NULL_TREE) + ++idx; + write_prefix (ctx); + write_compact_number (idx); + } else if (strcmp (prefix, "un") == 0) { tree ctx = DECL_CONTEXT (arg); diff --git a/gcc/testsuite/g++.dg/reflect/mangle1.C b/gcc/testsuite/g++.dg/reflect/mangle1.C index e0e609943122..e0232837e662 100644 --- a/gcc/testsuite/g++.dg/reflect/mangle1.C +++ b/gcc/testsuite/g++.dg/reflect/mangle1.C @@ -15,6 +15,7 @@ struct S : B { int : 0; static int var; }; +struct W { union {}; union {}; union {}; union {}; }; template <auto> struct TCls {}; template <auto> void TFn (); template <auto> int TVar; @@ -172,6 +173,8 @@ baz (int x) std::meta::reflect_constant (43L), std::meta::reflect_constant (NS2::AA { 1, 2 }) } })> (); // data member description bar <340, ^^NS2::X::~X> (); // function + bar <350, members_of (^^W, ctx)[1]> (); // empty anon union non-static data member + bar <351, members_of (^^W, ctx)[7]> (); // empty anon union non-static data member } // { dg-final { scan-assembler "_Z3fooILi1EDmEvv" } } @@ -258,3 +261,5 @@ baz (int x) // { dg-final { scan-assembler "_Z3barILi334ELDmdsi___0_EEvv" } } // { dg-final { scan-assembler "_Z3barILi335ELDmdsi_1____Li42ELl43EXtlN3NS22AAELi1ELi2EEEEEvv" } } // { dg-final { scan-assembler "_Z3barILi340ELDmfnN3NS21XD4EvEEvv" } } +// { dg-final { scan-assembler "_Z3barILi350ELDmda1W_EEvv" } } +// { dg-final { scan-assembler "_Z3barILi351ELDmda1W2_EEvv" } } diff --git a/gcc/testsuite/g++.dg/reflect/mangle9.C b/gcc/testsuite/g++.dg/reflect/mangle9.C new file mode 100644 index 000000000000..1f78daa6dd56 --- /dev/null +++ b/gcc/testsuite/g++.dg/reflect/mangle9.C @@ -0,0 +1,31 @@ +// { dg-do compile { target c++26 } } +// { dg-options "-freflection -O0" } + +#include <meta> + +struct W { union { union {}; union {}; union {}; union {}; }; + union { union {}; union {}; union {}; union {}; }; }; + +constexpr auto ctx = std::meta::access_context::current (); + +template <int N, std::meta::info I> +void +bar () +{ +} + +void +baz (int x) +{ + constexpr auto a = members_of (^^W, ctx)[0]; + bar <10, members_of (a, ctx)[1]> (); // empty anon union non-static data member + bar <11, members_of (a, ctx)[7]> (); // empty anon union non-static data member + constexpr auto b = members_of (^^W, ctx)[2]; + bar <12, members_of (b, ctx)[1]> (); // empty anon union non-static data member + bar <13, members_of (b, ctx)[7]> (); // empty anon union non-static data member +} + +// { dg-final { scan-assembler "_Z3barILi10ELDmda1WUt__EEvv" } } +// { dg-final { scan-assembler "_Z3barILi11ELDmda1WUt_2_EEvv" } } +// { dg-final { scan-assembler "_Z3barILi12ELDmda1WUt0__EEvv" } } +// { dg-final { scan-assembler "_Z3barILi13ELDmda1WUt0_2_EEvv" } }
