[gcc r15-9861] Fortran: Source allocation of pure function result rejected [PR119948]

[Jerry DeLisle]

https://gcc.gnu.org/g:8422524f6f43263caca2c2ab8a0e890e92f5f114

commit r15-9861-g8422524f6f43263caca2c2ab8a0e890e92f5f114
Author: Paul Thomas <pault@gcc.gnu.org>
Date:   Thu May 1 15:22:54 2025 +0100

    Fortran: Source allocation of pure function result rejected [PR119948]
    
    2025-05-07  Paul Thomas  <pault@gcc.gnu.org>
                and Steven G. Kargl  <kargl@gcc.gnu.org>
    
    gcc/fortran
            PR fortran/119948
            * resolve.cc (gfc_impure_variable): The result of a module
            procedure with an interface declaration is not impure even if
            the current namespace is not the same as the symbol's.
            * primary.cc (match_variable): Module procedures with sym the
            same as result can be treated as variables, although marked
            external.
    
    gcc/testsuite/
            PR fortran/119948
            * gfortran.dg/pr119948.f90: New test.
    
    (cherry picked from commit 0abc77da9d704bba55a376bb5c162a54826ab94a)

Diff:
---
 gcc/fortran/primary.cc                 |  2 +-
 gcc/fortran/resolve.cc                 | 10 ++++
 gcc/testsuite/gfortran.dg/pr119948.f90 | 83 ++++++++++++++++++++++++++++++++++
 3 files changed, 94 insertions(+), 1 deletion(-)

diff --git a/gcc/fortran/primary.cc b/gcc/fortran/primary.cc
index b5dddde5481b..f0e1fef6812e 100644
--- a/gcc/fortran/primary.cc
+++ b/gcc/fortran/primary.cc
@@ -4448,7 +4448,7 @@ match_variable (gfc_expr **result, int equiv_flag, int host_flag)
     case FL_PROCEDURE:
       /* Check for a nonrecursive function result variable.  */
       if (sym->attr.function
-	  && !sym->attr.external
+	  && (!sym->attr.external || sym->abr_modproc_decl)
 	  && sym->result == sym
 	  && (gfc_is_function_return_value (sym, gfc_current_ns)
 	      || (sym->attr.entry
diff --git a/gcc/fortran/resolve.cc b/gcc/fortran/resolve.cc
index c5c10205dadf..ee5b22a728d4 100644
--- a/gcc/fortran/resolve.cc
+++ b/gcc/fortran/resolve.cc
@@ -18478,6 +18478,16 @@ gfc_impure_variable (gfc_symbol *sym)
   if (sym->attr.use_assoc || sym->attr.in_common)
     return 1;
 
+  /* The namespace of a module procedure interface holds the arguments and
+     symbols, and so the symbol namespace can be different to that of the
+     procedure.  */
+  if (sym->ns != gfc_current_ns
+      && gfc_current_ns->proc_name->abr_modproc_decl
+      && sym->ns->proc_name->attr.function
+      && sym->attr.result
+      && !strcmp (sym->ns->proc_name->name, gfc_current_ns->proc_name->name))
+    return 0;
+
   /* Check if the symbol's ns is inside the pure procedure.  */
   for (ns = gfc_current_ns; ns; ns = ns->parent)
     {
diff --git a/gcc/testsuite/gfortran.dg/pr119948.f90 b/gcc/testsuite/gfortran.dg/pr119948.f90
new file mode 100644
index 000000000000..2e36fae5a9de
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr119948.f90
@@ -0,0 +1,83 @@
+! { dg-do run }
+!
+! Test the fix for PR119948, which used to fail as indicated below with:
+! (1) "Error: Bad allocate-object at (1) for a PURE procedure"
+! (2) "Error: ‘construct_test2 at (1) is not a variable"
+!
+! Contributed by Damian Rouson  <damian@archaeologic.codes>
+!
+module test_m
+  implicit none
+
+  type test_t
+    integer, allocatable :: i
+  end type
+
+  interface
+    pure module function construct_test(arg) result(test)
+      implicit none
+      type(test_t) :: test
+      type(test_t), intent(in) :: arg
+    end function
+
+    pure module function construct_test2(arg)
+      implicit none
+      type(test_t) construct_test2
+      type(test_t), intent(in) :: arg
+    end function
+
+    pure module function construct_test_3(arg) result(test)
+      implicit none
+      type(test_t) :: test
+      type(test_t), intent(in) :: arg
+    end function
+
+    pure module function construct_test_4(arg)
+      implicit none
+      type(test_t) :: construct_test_4
+      type(test_t), intent(in) :: arg
+    end function
+  end interface
+
+contains
+  module procedure construct_test
+    allocate(test%i, source = arg%i) ! Fail #1
+  end procedure
+
+  module procedure construct_test2
+    allocate(construct_test2%i, source = arg%i)    ! Fail #2
+  end procedure
+end module
+
+submodule (test_m)test_s
+contains
+  module procedure construct_test_3
+    allocate(test%i, source = arg%i) ! This was OK.
+  end procedure
+
+  module procedure construct_test_4
+    allocate(construct_test_4%i, source = arg%i) ! This was OK.
+  end procedure
+end submodule
+
+  use test_m
+  type(test_t) :: res, dummy
+!
+  dummy%i = int (rand () * 1e6)
+  res = construct_test (dummy)
+  if (res%i /= dummy%i) stop 1
+!
+  dummy%i = int (rand () * 1e6)
+  res = construct_test2 (dummy)
+  if (res%i /= dummy%i) stop 2
+!
+  dummy%i = int (rand () * 1e6)
+  res = construct_test_3 (dummy)
+  if (res%i /= dummy%i) stop 3
+
+  dummy%i = int (rand () * 1e6)
+  res = construct_test_4 (dummy)
+  if (res%i /= dummy%i) stop 4
+
+  deallocate (res%i, dummy%i)
+end