https://gcc.gnu.org/g:a880082f559dcc0d8c3bfd6c60e38cb3151eb0d9
commit r16-9033-ga880082f559dcc0d8c3bfd6c60e38cb3151eb0d9 Author: Jakub Jelinek <[email protected]> Date: Sat May 30 17:49:18 2026 +0200 c++: Don't ICE on the static constexpr expansion-stmt vars during mangling [PR125123] The following testcase ICEs, because we decide to mangle the (for the time being as workaround static constexpr variables created for expansion statements). And if there is more than one in the same function and we mangle both, we ICE because they mangle the same. The problem is that cp_finish_decl does not determine_local_discriminator for DECL_ARTIFICIAL vars. The following patch fixes that by calling it even for DECL_ARTIFICIAL vars. The patch also sets DECL_IGNORED_P on those vars, I think there is no value exposing those in the debug information, the iterating is done at compile time and all user IMHO cares are the individual user variables initialized to whatever was derived from the temporaries. 2026-05-29 Jakub Jelinek <[email protected]> PR c++/125123 * parser.cc (cp_build_range_for_decls): If range_temp or begin are static, set DECL_IGNORED_P on it. * pt.cc (finish_expansion_stmt): Similarly for iter. * decl.cc (cp_finish_decl): Call determine_local_discriminator etc. also for DECL_ARTIFICIAL TREE_STATIC vars. * g++.dg/cpp26/expansion-stmt42.C: New test. Reviewed-by: Jason Merrill <[email protected]> (cherry picked from commit 833722e02b083a5828e0f7dbf67ae5456755f0de) Diff: --- gcc/cp/decl.cc | 4 +--- gcc/cp/parser.cc | 2 ++ gcc/cp/pt.cc | 1 + gcc/testsuite/g++.dg/cpp26/expansion-stmt42.C | 22 ++++++++++++++++++++++ 4 files changed, 26 insertions(+), 3 deletions(-) diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc index d2c66c902753..04e685252dee 100644 --- a/gcc/cp/decl.cc +++ b/gcc/cp/decl.cc @@ -9887,9 +9887,7 @@ cp_finish_decl (tree decl, tree init, bool init_const_expr_p, require a guard variable, and since the mangled name of the guard variable will depend on the mangled name of this variable. */ - if (DECL_FUNCTION_SCOPE_P (decl) - && TREE_STATIC (decl) - && !DECL_ARTIFICIAL (decl)) + if (DECL_FUNCTION_SCOPE_P (decl) && TREE_STATIC (decl)) { /* The variable holding an anonymous union will have had its discriminator set in finish_anon_union, after which it's diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc index 449ed491dd8c..cc3ee315436a 100644 --- a/gcc/cp/parser.cc +++ b/gcc/cp/parser.cc @@ -16063,6 +16063,7 @@ cp_build_range_for_decls (location_t loc, tree range_expr, tree *end_p, DECL_INTERFACE_KNOWN (range_temp) = 1; DECL_DECLARED_CONSTEXPR_P (range_temp) = 1; TREE_READONLY (range_temp) = 1; + DECL_IGNORED_P (range_temp) = 1; } } else @@ -16092,6 +16093,7 @@ cp_build_range_for_decls (location_t loc, tree range_expr, tree *end_p, TREE_STATIC (begin) = 1; DECL_DECLARED_CONSTEXPR_P (begin) = 1; TREE_READONLY (begin) = 1; + DECL_IGNORED_P (begin) = 1; } pushdecl (begin); cp_finish_decl (begin, begin_expr, diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index b6302b592253..d704665c3fb4 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -33696,6 +33696,7 @@ finish_expansion_stmt (tree expansion_stmt, tree args, TREE_STATIC (iter) = 1; DECL_DECLARED_CONSTEXPR_P (iter) = 1; TREE_READONLY (iter) = 1; + DECL_IGNORED_P (iter) = 1; } pushdecl (iter); cp_finish_decl (iter, iter_init, /*is_constant_init*/false, diff --git a/gcc/testsuite/g++.dg/cpp26/expansion-stmt42.C b/gcc/testsuite/g++.dg/cpp26/expansion-stmt42.C new file mode 100644 index 000000000000..240fa2a43f28 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp26/expansion-stmt42.C @@ -0,0 +1,22 @@ +// PR c++/125123 +// { dg-do compile { target c++20 } } +// { dg-options "-g" } + +struct A +{ + int a[2]; + constexpr int const *begin () const { return a; } + constexpr int const *end () const { return a + 2; } +}; + +template <typename T> +requires true +void +foo () +{ + template for (constexpr int i : A { 0, 1 }) // { dg-warning "'template for' only available with" "" { target c++23_down } } + ; + template for (constexpr int i : A { 0, 1 }) // { dg-warning "'template for' only available with" "" { target c++23_down } } + ; +} +template void foo <void> ();
