https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109756
--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-13 branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:7bd9a34e9fce0fc307ec26d6db071fe0bc02cd37 commit r13-7312-g7bd9a34e9fce0fc307ec26d6db071fe0bc02cd37 Author: Jakub Jelinek <ja...@redhat.com> Date: Tue May 9 16:05:22 2023 +0200 c++: Reject pack expansion of assume attribute [PR109756] http://eel.is/c++draft/dcl.attr#grammar-4 says "In an attribute-list, an ellipsis may appear only if that attribute's specification permits it." and doesn't explicitly permit it on any standard attribute. The https://wg21.link/p1774r8 paper which introduced assume attribute says "We could therefore hypothetically permit the assume attribute to directly support pack expansion: template <int... args> void f() { [[assume(args >= 0)...]]; } However, we do not propose this. It would require substantial additional work for a very rare use case. Note that this can instead be expressed with a fold expression, which is equivalent to the above and works out of the box without any extra effort: template <int... args> void f() { [[assume(((args >= 0) && ...))]]; } ", but as the testcase shows, GCC 13+ ICEs on assume attribute followed by ... if it contains packs. The following patch rejects those instead of ICE and for C++17 or later suggests using fold expressions instead (it doesn't make sense to suggest it for C++14 and earlier when we'd error on the fold expressions). 2023-05-09 Jakub Jelinek <ja...@redhat.com> PR c++/109756 * cp-gimplify.cc (process_stmt_assume_attribute): Diagnose pack expansion of assume attribute. * g++.dg/cpp23/attr-assume11.C: New test. (cherry picked from commit 2499540e9abb55079b5f7b7ccdac97fbc63d9ab4)
