[PATCH, committed] Fortran: do not generate conflicting results under -ff2c [PR104313]

[Harald Anlauf <anlauf@gmx.de>]

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Dear all,

the attached patch by Steve fixes a regression under -ff2c for functions
where the result is not set.  There would otherwise be conflicting
declarations of the returned result, which gimple doesn't like.

I've committed this as obvious after discussion with Steve for him,
see PR, as

commit r13-1715-g517fb1a78102df43f052c6934c27dd51d786aff7

This fixes a 10/11/12/13 regression, will be backported in the next days.

Thanks,
Harald


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From 517fb1a78102df43f052c6934c27dd51d786aff7 Mon Sep 17 00:00:00 2001
From: Steve Kargl <kargl@gcc.gnu.org>
Date: Fri, 15 Jul 2022 22:07:15 +0200
Subject: [PATCH] Fortran: do not generate conflicting results under -ff2c
 [PR104313]

gcc/fortran/ChangeLog:

	PR fortran/104313
	* trans-decl.cc (gfc_generate_return): Do not generate conflicting
	fake results for functions with no result variable under -ff2c.

gcc/testsuite/ChangeLog:

	PR fortran/104313
	* gfortran.dg/pr104313.f: New test.
---
 gcc/fortran/trans-decl.cc            |  2 +-
 gcc/testsuite/gfortran.dg/pr104313.f | 11 +++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gfortran.dg/pr104313.f

diff --git a/gcc/fortran/trans-decl.cc b/gcc/fortran/trans-decl.cc
index 6493cc2f6b1..908a4c6d42e 100644
--- a/gcc/fortran/trans-decl.cc
+++ b/gcc/fortran/trans-decl.cc
@@ -6474,7 +6474,7 @@ gfc_generate_return (void)
 	     NULL_TREE, and a 'return' is generated without a variable.
 	     The following generates a 'return __result_XXX' where XXX is
 	     the function name.  */
-	  if (sym == sym->result && sym->attr.function)
+	  if (sym == sym->result && sym->attr.function && !flag_f2c)
 	    {
 	      result = gfc_get_fake_result_decl (sym, 0);
 	      result = fold_build2_loc (input_location, MODIFY_EXPR,
diff --git a/gcc/testsuite/gfortran.dg/pr104313.f b/gcc/testsuite/gfortran.dg/pr104313.f
new file mode 100644
index 00000000000..89c8947cb0a
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr104313.f
@@ -0,0 +1,11 @@
+! { dg-do compile }
+! { dg-additional-options "-ff2c -fdump-tree-original" }
+!
+! PR fortran/104313 - ICE verify_gimple failed with -ff2c
+! Contributed by G.Steinmetz
+
+      function f(a)
+      return
+      end
+
+! { dg-final { scan-tree-dump-times "return" 1 "original" } }
--
2.35.3