https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118961
--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Nathaniel Shead <nsh...@gcc.gnu.org>: https://gcc.gnu.org/g:3258c89fbb092412a69b689425e77972e7a1c567 commit r15-9024-g3258c89fbb092412a69b689425e77972e7a1c567 Author: Nathaniel Shead <nathanielosh...@gmail.com> Date: Fri Mar 28 23:38:26 2025 +1100 c++/modules: Fix modules and LTO with header units [PR118961] This patch makes some adjustments required to get a simple modules testcase working with LTO. There are two main issues fixed. Firstly, modules only streams the maybe-in-charge constructor, and any clones are recreated on stream-in. These clones are copied from the existing function decl and then adjusted. This caused issues because the clones were getting incorrectly marked as abstract, since after clones have been created (in the imported file) the maybe-in-charge decl gets marked as abstract. So this patch just ensures that clones are always created as non-abstract. The second issue is that we need to explicitly tell cgraph that explicit instantiations need to be emitted, otherwise LTO will elide them (as they don't necessarily appear to be used directly) and cause link errors. Additionally, expand_or_defer_fn doesn't setup comdat groups for explicit instantiations, so we need to do that here as well. Currently this is all handled in 'mark_decl_instantiated'; this patch splits out the linkage handling into a separate function that we can call from modules code, maybe in GCC16 we could move this somewhere more central. PR c++/118961 gcc/cp/ChangeLog: * class.cc (copy_fndecl_with_name): Mark clones as non-abstract. * cp-tree.h (setup_explicit_instantiation_definition_linkage): Declare new function. * module.cc (trees_in::read_var_def): Use it. (module_state::read_cluster): Likewise. * pt.cc (setup_explicit_instantiation_definition_linkage): New function. (mark_decl_instantiated): Use it. gcc/testsuite/ChangeLog: * g++.dg/modules/lto-1.h: New test. * g++.dg/modules/lto-1_a.H: New test. * g++.dg/modules/lto-1_b.C: New test. * g++.dg/modules/lto-1_c.C: New test. * g++.dg/modules/lto-2_a.H: New test. * g++.dg/modules/lto-2_b.C: New test. * g++.dg/modules/lto-3_a.H: New test. * g++.dg/modules/lto-3_b.C: New test. Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com> Reviewed-by: Jason Merrill <ja...@redhat.com>
