[PATCH] Fortran, Allow task-reduction allocatable scalars without, outer ref [PR102596]

From aba89bd758f1ddb3d42ca41260b872198ccdc511 Mon Sep 17 00:00:00 2001
From: Christopher Albert <[email protected]>
Date: Tue, 10 Mar 2026 19:16:24 +0100
Subject: [PATCH] fortran: Allow task-reduction allocatable scalars without
 outer ref [PR102596]

OpenMP task reduction lowering can call gfc_omp_clause_default_ctor for
an allocatable scalar with outer == NULL_TREE.  That is valid for scalar
allocatables that only need fresh storage allocation and do not need a
copied descriptor or allocatable-component walk.

The Fortran hook asserted unconditionally on outer != NULL_TREE, so
reduction(task, +:r) with an allocatable scalar ICEd during omplower.

Fix this by requiring outer only for the cases that actually use it:
descriptor-based allocatables and types with allocatable components.
Keep the assertion for those cases and allow NULL outer for plain scalar
allocatables.  Add a regression test for the allocatable task-reduction
case.

gcc/fortran/ChangeLog:

	PR fortran/102596
	* trans-openmp.cc (gfc_omp_clause_default_ctor): Only require an
	outer reference when the constructor path actually uses it.

gcc/testsuite/ChangeLog:

	PR fortran/102596
	* gfortran.dg/pr102596.f90: New test.

Signed-off-by: Christopher Albert <[email protected]>
---
 gcc/fortran/trans-openmp.cc            |  5 ++++-
 gcc/testsuite/gfortran.dg/pr102596.f90 | 13 +++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gfortran.dg/pr102596.f90

diff --git a/gcc/fortran/trans-openmp.cc b/gcc/fortran/trans-openmp.cc
index 3dd4cf272e5..2842a0c191c 100644
--- a/gcc/fortran/trans-openmp.cc
+++ b/gcc/fortran/trans-openmp.cc
@@ -815,7 +815,10 @@ gfc_omp_clause_default_ctor (tree clause, tree decl, tree outer)
       return NULL_TREE;
     }
 
-  gcc_assert (outer != NULL_TREE);
+  gcc_assert (outer != NULL_TREE
+	      || (!GFC_DESCRIPTOR_TYPE_P (type)
+		  && !gfc_has_alloc_comps (type, OMP_CLAUSE_DECL (clause),
+					   false)));
 
   /* Allocatable arrays and scalars in PRIVATE clauses need to be set to
      "not currently allocated" allocation status if outer
diff --git a/gcc/testsuite/gfortran.dg/pr102596.f90 b/gcc/testsuite/gfortran.dg/pr102596.f90
new file mode 100644
index 00000000000..b8c3b2f72d7
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr102596.f90
@@ -0,0 +1,13 @@
+! { dg-do compile }
+! { dg-additional-options "-fopenmp" }
+
+program p
+  integer, allocatable :: r
+
+  allocate (r)
+  r = 0
+
+  !$omp target parallel reduction(task, +:r)
+  r = r + 1
+  !$omp end target parallel
+end
-- 
2.53.0