Dear All, the attached simple patch fixes a rather strange bug, where the used interface of external procedures apparently changed between successive procedure calls. It is funny that this was not discovered before, but the issue started only after the *first* time the dummy arguments of the affected procedures were processed.
Regtested on x86_64-pc-linux-gnu. OK for mainline? It appears that this issue exists since at least gcc-8. Therefore I would like to backport to at least 15-branch. Thanks, Harald
From 0a74ce5c533d6e28d091e98e3021215489349bc5 Mon Sep 17 00:00:00 2001 From: Harald Anlauf <[email protected]> Date: Thu, 9 Oct 2025 18:43:22 +0200 Subject: [PATCH] Fortran: fix "unstable" interfaces of external procedures [PR122206] In the testcase repeated invocations of a function showed an apparently unstable interface. This was caused by trying to guess an (inappropriate) interface of the external procedure after processing of the procedure arguments in gfc_conv_procedure_call. The mis-guessed interface showed up in subsequent uses of the procedure symbol in gfc_conv_procedure_call. The solution is to check for an existing interface of an external procedure before trying to wildly guess based on just the actual arguments. PR fortran/122206 gcc/fortran/ChangeLog: * trans-types.cc (gfc_get_function_type): Do not clobber an existing procedure interface. gcc/testsuite/ChangeLog: * gfortran.dg/interface_abstract_6.f90: New test. --- gcc/fortran/trans-types.cc | 1 + .../gfortran.dg/interface_abstract_6.f90 | 53 +++++++++++++++++++ 2 files changed, 54 insertions(+) create mode 100644 gcc/testsuite/gfortran.dg/interface_abstract_6.f90 diff --git a/gcc/fortran/trans-types.cc b/gcc/fortran/trans-types.cc index 26645b0f7f6..dfdac600c24 100644 --- a/gcc/fortran/trans-types.cc +++ b/gcc/fortran/trans-types.cc @@ -3441,6 +3441,7 @@ gfc_get_function_type (gfc_symbol * sym, gfc_actual_arglist *actual_args, } } if (sym->backend_decl == error_mark_node && actual_args != NULL + && sym->ts.interface == NULL && sym->formal == NULL && (sym->attr.proc == PROC_EXTERNAL || sym->attr.proc == PROC_UNKNOWN)) gfc_get_formal_from_actual_arglist (sym, actual_args); diff --git a/gcc/testsuite/gfortran.dg/interface_abstract_6.f90 b/gcc/testsuite/gfortran.dg/interface_abstract_6.f90 new file mode 100644 index 00000000000..05b9a4e805f --- /dev/null +++ b/gcc/testsuite/gfortran.dg/interface_abstract_6.f90 @@ -0,0 +1,53 @@ +! { dg-do compile } +! { dg-options "-fdump-tree-original" } +! +! PR fortran/122206 +! +! Verify that procedure interfaces are "stable" + +module test_example + use, intrinsic :: iso_c_binding, only: c_double, c_int + implicit none + + abstract interface + function simple_interface(iarg1, arg2) bind(c) result(res) + import c_double, c_int + integer(c_int), value, intent(in) :: iarg1 + real(c_double), value, intent(in) :: arg2 + real(c_double) :: res + end function simple_interface + end interface + + procedure(simple_interface), bind(c,name="simple_function") :: simple_function + + interface + function other_interface(iarg1, arg2) result(res) + import c_double, c_int + integer(c_int), value, intent(in) :: iarg1 + real(c_double), value, intent(in) :: arg2 + real(c_double) :: res + end function other_interface + end interface + + procedure(other_interface) :: other_function + +contains + subroutine test_example_interface + implicit none + integer(c_int) :: iarg1 = 2 + real(c_double) :: arg2 = 10. + real(c_double) :: val1, val2 + + val1 = simple_function(iarg1, arg2) + val2 = simple_function(iarg1, arg2) + if (val1 /= val2) stop 1 + + val1 = other_function(iarg1, arg2) + val2 = other_function(iarg1, arg2) + if (val1 /= val2) stop 2 + + end subroutine test_example_interface +end module test_example + +! { dg-final { scan-tree-dump-times "simple_function \\(iarg1, arg2\\);" 2 "original"} } +! { dg-final { scan-tree-dump-times "other_function \\(iarg1, arg2\\);" 2 "original"} } -- 2.51.0
