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Fortran: fix associate with assumed-length character array [PR115700]

Message ID trinity-d671bc85-0a8c-4f8c-8535-99cdbb83ab59-1719949441099@3c-app-gmx-bs32
State New
Headers show
Series Fortran: fix associate with assumed-length character array [PR115700] | expand

Commit Message

Harald Anlauf July 2, 2024, 7:44 p.m. UTC 
Dear all,

the attached patch addresses an effectively bogus warning about
uninitialized temporary string lengths of associate selectors.
The primary reason is that the array descriptor for a character
array is created before the corresponding string length is set.
Moving the setting of the string length temporary to the beginning
of the block solves the issue.

The patch does not solve the case for the target containing
substring references.  This needs to be addressed separately.
(So far I could not find a solution that does not regress.)

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

As the PR is marked as a regression, is it also OK for backporting?

Thanks,
Harald

Comments

Andre Vehreschild July 3, 2024, 7:15 a.m. UTC | #1 
Hi Harald,

that patch looks fine to me. I'd say ok for mainline. Give it some time there
and then backport it.

Thanks for the patch.

Regards,
	Andre

On Tue, 2 Jul 2024 21:44:01 +0200
Harald Anlauf <anlauf@gmx.de> wrote:

> Dear all,
>
> the attached patch addresses an effectively bogus warning about
> uninitialized temporary string lengths of associate selectors.
> The primary reason is that the array descriptor for a character
> array is created before the corresponding string length is set.
> Moving the setting of the string length temporary to the beginning
> of the block solves the issue.
>
> The patch does not solve the case for the target containing
> substring references.  This needs to be addressed separately.
> (So far I could not find a solution that does not regress.)
>
> Regtested on x86_64-pc-linux-gnu.  OK for mainline?
>
> As the PR is marked as a regression, is it also OK for backporting?
>
> Thanks,
> Harald
>


--
Andre Vehreschild * Email: vehre ad gmx dot de
diff mbox series

Patch

From 930a1be8c623cf03f9b2e6dbddb45d0b69e152dd Mon Sep 17 00:00:00 2001
From: Harald Anlauf <anlauf@gmx.de>
Date: Tue, 2 Jul 2024 21:26:05 +0200
Subject: [PATCH] Fortran: fix associate with assumed-length character array
 [PR115700]

gcc/fortran/ChangeLog:

	PR fortran/115700
	* trans-stmt.cc (trans_associate_var): When the associate target
	is an array-valued character variable, the length is known at entry
	of the associate block.  Move setting of string length of the
	selector to the initialization part of the block.

gcc/testsuite/ChangeLog:

	PR fortran/115700
	* gfortran.dg/associate_69.f90: New test.
---
 gcc/fortran/trans-stmt.cc                  | 18 +++++++++---
 gcc/testsuite/gfortran.dg/associate_69.f90 | 33 ++++++++++++++++++++++
 2 files changed, 47 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/gfortran.dg/associate_69.f90

diff --git a/gcc/fortran/trans-stmt.cc b/gcc/fortran/trans-stmt.cc
index 60275e18867..703a705e7ca 100644
--- a/gcc/fortran/trans-stmt.cc
+++ b/gcc/fortran/trans-stmt.cc
@@ -1911,6 +1911,8 @@  trans_associate_var (gfc_symbol *sym, gfc_wrapped_block *block)
       gfc_se se;
       tree desc;
       bool cst_array_ctor;
+      stmtblock_t init;
+      gfc_init_block (&init);

       desc = sym->backend_decl;
       cst_array_ctor = e->expr_type == EXPR_ARRAY
@@ -1935,10 +1937,17 @@  trans_associate_var (gfc_symbol *sym, gfc_wrapped_block *block)
 	  && !sym->attr.select_type_temporary
 	  && sym->ts.u.cl->backend_decl
 	  && VAR_P (sym->ts.u.cl->backend_decl)
+	  && se.string_length
 	  && se.string_length != sym->ts.u.cl->backend_decl)
-	gfc_add_modify (&se.pre, sym->ts.u.cl->backend_decl,
-			  fold_convert (TREE_TYPE (sym->ts.u.cl->backend_decl),
-					se.string_length));
+	{
+	  /* When the target is a variable, its length is already known.  */
+	  tree len = fold_convert (TREE_TYPE (sym->ts.u.cl->backend_decl),
+				   se.string_length);
+	  if (e->expr_type == EXPR_VARIABLE)
+	    gfc_add_modify (&init, sym->ts.u.cl->backend_decl, len);
+	  else
+	    gfc_add_modify (&se.pre, sym->ts.u.cl->backend_decl, len);
+	}

       /* If we didn't already do the pointer assignment, set associate-name
 	 descriptor to the one generated for the temporary.  */
@@ -1978,7 +1987,8 @@  trans_associate_var (gfc_symbol *sym, gfc_wrapped_block *block)
 	}

       /* Done, register stuff as init / cleanup code.  */
-      gfc_add_init_cleanup (block, gfc_finish_block (&se.pre),
+      gfc_add_block_to_block (&init, &se.pre);
+      gfc_add_init_cleanup (block, gfc_finish_block (&init),
 			    gfc_finish_block (&se.post));
     }

diff --git a/gcc/testsuite/gfortran.dg/associate_69.f90 b/gcc/testsuite/gfortran.dg/associate_69.f90
new file mode 100644
index 00000000000..28f488bb274
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/associate_69.f90
@@ -0,0 +1,33 @@ 
+! { dg-do compile }
+! { dg-options "-Og -Wuninitialized -Wmaybe-uninitialized -fdump-tree-optimized" }
+!
+! PR fortran/115700 - Bogus warning for associate with assumed-length character array
+!
+subroutine mvce(x)
+  implicit none
+  character(len=*), dimension(:), intent(in)  :: x
+
+  associate (tmp1 => x)
+    if (len (tmp1) /= len (x)) stop 1
+  end associate
+
+  associate (tmp2 => x(1:))
+    if (len (tmp2) /= len (x)) stop 2
+  end associate
+
+  associate (tmp3 => x(1:)(:))
+    if (len (tmp3) /= len (x)) stop 3
+  end associate
+
+! The following associate blocks still produce bogus warnings:
+
+! associate (tmp4 => x(:)(1:))
+!   if (len (tmp4) /= len (x)) stop 4
+! end associate
+!
+! associate (tmp5 => x(1:)(1:))
+!   if (len (tmp5) /= len (x)) stop 5
+! end associate
+end
+
+! { dg-final { scan-tree-dump-not " \\.tmp" "optimized" } }
--
2.35.3