As reported in <http://mid.mail-archive.com/20181004140413.2147eca1@squid.athome>.
Author: tschwinge Date: Tue Jun 18 22:15:53 2019 New Revision: 272454 URL: https://gcc.gnu.org/viewcvs?rev=272454&root=gcc&view=rev Log: [PR90921] Fortran OpenACC 'declare' directive's module handling causes duplicate data clauses gcc/fortran/ PR fortran/90921 * trans-decl.c (finish_oacc_declare): Reset module_oacc_clauses before scanning each namespace. gcc/testsuite/ PR fortran/90921 * gfortran.dg/goacc/declare-3.f95: Update. Modified: trunk/gcc/fortran/ChangeLog trunk/gcc/fortran/trans-decl.c trunk/gcc/testsuite/ChangeLog trunk/gcc/testsuite/gfortran.dg/goacc/declare-3.f95
A patch for this was committed in June 2019 – hence, for GCC trunk = GCC 10. Can this be closed? – Or do you want to backport it or/and is there something else still missing?