https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122015
--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-15 branch has been updated by Nathaniel Shead <[email protected]>: https://gcc.gnu.org/g:217066a4635c951afccf54de9d98432750371353 commit r15-10348-g217066a4635c951afccf54de9d98432750371353 Author: Nathaniel Shead <[email protected]> Date: Tue Sep 23 00:18:43 2025 +1000 c++: Fix canonical type for lambda pack captures [PR122015] comp_template_parms_position uses whether a TEMPLATE_TYPE_PARM is a pack to determine equivalency. This in turn affects whether canonical_type_parameter finds a pre-existing auto type as equivalent. When generating the 'auto...' type for a lambda pack capture, we only mark it as a pack after generating the node (and calculating its canonical); this means that later when comparing a version streamed in from a module we think that two equivalent types have different TYPE_CANONICAL, because the latter already had TEMPLATE_PARM_PARAMETER_PACK set before calculating its canonical. This patch fixes this by using a new 'make_auto_pack' function to ensure that packness is set before the canonical is looked up. PR c++/122015 gcc/cp/ChangeLog: * cp-tree.h (make_auto_pack): Declare. * lambda.cc (lambda_capture_field_type): Use make_auto_pack to ensure TYPE_CANONICAL is set correctly. * pt.cc (make_auto_pack): New function. gcc/testsuite/ChangeLog: * g++.dg/modules/lambda-11.h: New test. * g++.dg/modules/lambda-11_a.H: New test. * g++.dg/modules/lambda-11_b.C: New test. Signed-off-by: Nathaniel Shead <[email protected]> Reviewed-by: Patrick Palka <[email protected]> (cherry picked from commit cc79849cc883146964f0001f33c8b7eb576825c4)
