[PATCH] Fortran: diagnostics of MODULE PROCEDURE declaration conflicts [PR104649]

[Harald Anlauf <anlauf@gmx.de>]

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Dear all,

the attached patch improves the diagnostics of MODULE PROCEDURE declaration
conflicts, when one of the declarations is an alternate return.  We used to
ICE before.

Steve identified the cause of the issue and provided a partial fix.

Regtested on x86_64-pc-linux-gnu.  OK for mainline?

Thanks,
Harald


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From 9d591a73f070e6090b7c59dca928b84b1c261d92 Mon Sep 17 00:00:00 2001
From: Harald Anlauf <anlauf@gmx.de>
Date: Thu, 26 Oct 2023 22:32:35 +0200
Subject: [PATCH] Fortran: diagnostics of MODULE PROCEDURE declaration
 conflicts [PR104649]

gcc/fortran/ChangeLog:

	PR fortran/104649
	* decl.cc (gfc_match_formal_arglist): Handle conflicting declarations
	of a MODULE PROCEDURE when one of the declarations is an alternate
	return.

gcc/testsuite/ChangeLog:

	PR fortran/104649
	* gfortran.dg/pr104649.f90: New test.

Co-authored-by: Steven G. Kargl <kargl@gcc.gnu.org>
---
 gcc/fortran/decl.cc                    | 21 +++++++++---
 gcc/testsuite/gfortran.dg/pr104649.f90 | 44 ++++++++++++++++++++++++++
 2 files changed, 61 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/gfortran.dg/pr104649.f90

diff --git a/gcc/fortran/decl.cc b/gcc/fortran/decl.cc
index bdd3be32a46..4893c582065 100644
--- a/gcc/fortran/decl.cc
+++ b/gcc/fortran/decl.cc
@@ -6796,12 +6796,25 @@ ok:
 	      || (p->next == NULL && q->next != NULL))
 	    arg_count_mismatch = true;
 	  else if ((p->sym == NULL && q->sym == NULL)
-		    || strcmp (p->sym->name, q->sym->name) == 0)
+		    || (p->sym && q->sym
+			&& strcmp (p->sym->name, q->sym->name) == 0))
 	    continue;
 	  else
-	    gfc_error_now ("Mismatch in MODULE PROCEDURE formal "
-			   "argument names (%s/%s) at %C",
-			   p->sym->name, q->sym->name);
+	    {
+	      if (q->sym == NULL)
+		gfc_error_now ("MODULE PROCEDURE formal argument %qs "
+			       "conflicts with alternate return at %C",
+			       p->sym->name);
+	      else if (p->sym == NULL)
+		gfc_error_now ("MODULE PROCEDURE formal argument is "
+			       "alternate return and conflicts with "
+			       "%qs in the separate declaration at %C",
+			       q->sym->name);
+	      else
+		gfc_error_now ("Mismatch in MODULE PROCEDURE formal "
+			       "argument names (%s/%s) at %C",
+			       p->sym->name, q->sym->name);
+	    }
 	}

       if (arg_count_mismatch)
diff --git a/gcc/testsuite/gfortran.dg/pr104649.f90 b/gcc/testsuite/gfortran.dg/pr104649.f90
new file mode 100644
index 00000000000..f301ffcde1f
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr104649.f90
@@ -0,0 +1,44 @@
+! { dg-do compile }
+! { dg-options "-w" }
+! PR fortran/104649
+! Contributed by G.Steinmetz
+
+module m
+  interface
+    module subroutine s(x)
+      real :: x
+    end
+  end interface
+end
+submodule(m) m2
+contains
+  module subroutine s(*) ! { dg-error "conflicts with alternate return" }
+  end
+end
+
+module n
+  interface
+     module subroutine s(*)
+     end
+  end interface
+end
+submodule(n) n2
+contains
+  module subroutine s(x) ! { dg-error "formal argument is alternate return" }
+    real :: x
+  end
+end
+
+module p
+  interface
+     module subroutine s(x)
+       real :: x
+     end
+  end interface
+end
+submodule(p) p2
+contains
+  module subroutine s(y) ! { dg-error "Mismatch in MODULE PROCEDURE formal argument names" }
+    real :: y
+  end
+end
--
2.35.3