This patch fixes PR96312. Cures a used uninitialized warning.

2020-08-10  Paul Thomas  <pault@gcc.gnu.org>

gcc/fortran
	PR fortran/96312
	* trans-expr.c (fcncall_realloc_result): Only compare shapes if
	lhs was allocated..

gcc/testsuite/
	PR fortran/96312
	* gfortran.dg/pr96312.f90: New test.

diff --git a/gcc/fortran/trans-expr.c b/gcc/fortran/trans-expr.c
index b7c568e..36ff9b5 100644 (file)
--- a/gcc/fortran/trans-expr.c
+++ b/gcc/fortran/trans-expr.c
@@ -9936,6 +9936,8 @@ fcncall_realloc_result (gfc_se *se, int rank)
   tree tmp;
   tree offset;
   tree zero_cond;
+  tree not_same_shape;
+  stmtblock_t shape_block;
   int n;
 
   /* Use the allocation done by the library.  Substitute the lhs
@@ -9965,7 +9967,11 @@ fcncall_realloc_result (gfc_se *se, int rank)
   tmp = gfc_conv_descriptor_data_get (res_desc);
   gfc_conv_descriptor_data_set (&se->post, desc, tmp);
 
-  /* Check that the shapes are the same between lhs and expression.  */
+  /* Check that the shapes are the same between lhs and expression.
+     The evaluation of the shape is done in 'shape_block' to avoid
+     unitialized warnings from the lhs bounds. */
+  not_same_shape = boolean_false_node;
+  gfc_start_block (&shape_block);
   for (n = 0 ; n < rank; n++)
     {
       tree tmp1;
@@ -9982,15 +9988,24 @@ fcncall_realloc_result (gfc_se *se, int rank)
       tmp = fold_build2_loc (input_location, NE_EXPR,
                             logical_type_node, tmp,
                             gfc_index_zero_node);
-      tmp = gfc_evaluate_now (tmp, &se->post);
-      zero_cond = fold_build2_loc (input_location, TRUTH_OR_EXPR,
-                                  logical_type_node, tmp,
-                                  zero_cond);
+      tmp = gfc_evaluate_now (tmp, &shape_block);
+      if (n == 0)
+       not_same_shape = tmp;
+      else
+       not_same_shape = fold_build2_loc (input_location, TRUTH_OR_EXPR,
+                                         logical_type_node, tmp,
+                                         not_same_shape);
     }
 
   /* 'zero_cond' being true is equal to lhs not being allocated or the
      shapes being different.  */
-  zero_cond = gfc_evaluate_now (zero_cond, &se->post);
+  tmp = fold_build2_loc (input_location, TRUTH_OR_EXPR, logical_type_node,
+                        zero_cond, not_same_shape);
+  gfc_add_modify (&shape_block, zero_cond, tmp);
+  tmp = gfc_finish_block (&shape_block);
+  tmp = build3_v (COND_EXPR, zero_cond,
+                 build_empty_stmt (input_location), tmp);
+  gfc_add_expr_to_block (&se->post, tmp);
 
   /* Now reset the bounds returned from the function call to bounds based
      on the lhs lbounds, except where the lhs is not allocated or the shapes

diff --git a/gcc/testsuite/gfortran.dg/pr96312.f90 b/gcc/testsuite/gfortran.dg/pr96312.f90
new file mode 100644 (file)
index 0000000..d6d8e79
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr96312.f90
@@ -0,0 +1,30 @@
+! { dg-do compile }
+! { dg-options "-O1 -Wall" }
+!
+! PR fortran/96312. The line with the call to 'matmul' gave the warning
+! ‘tmp.dim[0].lbound’ is used uninitialized in this function
+!
+! Contributed by Thomas Koenig  <tkoenig@gcc.gnu.org>
+!
+module moda
+contains
+   PURE SUBROUTINE funca(arr, sz)
+      REAL, ALLOCATABLE, DIMENSION(:, :), INTENT(OUT) :: arr
+      integer, intent(in) :: sz
+      allocate(arr(sz, sz))
+      arr(:, :) = 0.
+   END SUBROUTINE
+end module
+
+module modc
+    use moda, only: funca
+contains
+   PURE SUBROUTINE funcb(oarr)
+      REAL, DIMENSION(:), INTENT(OUT)    :: oarr
+      REAL, ALLOCATABLE, DIMENSION(:, :) :: arr
+      real, allocatable, dimension(:) :: tmp
+      CALL funca(arr, ubound(oarr, 1))
+      tmp = matmul(transpose(arr),oarr)
+      oarr = tmp*1.
+   END SUBROUTINE funcb
+end module