[PATCH] Fixing PR107411

[Qing Zhao <qing.zhao@oracle.com>]

This is a bug in tree-ssa-uninit.cc.
When doing the following:

  /* Ignore the call to .DEFERRED_INIT that define the original
     var itself as the following case:
       temp = .DEFERRED_INIT (4, 2, “alt_reloc");
       alt_reloc = temp;
     In order to avoid generating warning for the fake usage
     at alt_reloc = temp.
  */

We need to compare the var name inside the .DEFERRED_INIT call
(the 3rd argument) and the name for the LHS variable. if they are the same,
we will NOT report the warning.

There is one issue when we get the name for the LHS variable. when the
variable doesn't have a DECL_NAME (it's not a user declared variable,
which is the case for this bug):

  _1 = .DEFERRED_INIT (4, 2, &"D.2389"[0]);
  D.2389 = _1;

The current checking just ignores this case, and still report the warning.

The fix is very simple, when getting the name for the LHS variable, we should
consider this case and come up with the name the same way as we construct the
3rd argument for the call to .DEFERRED_INIT (please refer to the routine
"gimple_add_init_for_auto_var")

The patch has been bootstrapped and regression tested on both x86 and aarch64.
Okay for committing?

thanks.

Qing

	PR middle-end/107411

gcc/ChangeLog:

	PR middle-end/107411
	* tree-ssa-uninit.cc (warn_uninit): Handle the case when the
	LHS varaible of a .DEFERRED_INIT call doesn't have a DECL_NAME.

gcc/testsuite/ChangeLog:

	PR middle-end/107411
	* g++.dg/pr107411.C: New test.
---
 gcc/testsuite/g++.dg/pr107411.C | 10 ++++++++++
 gcc/tree-ssa-uninit.cc          | 27 ++++++++++++++++++++-------
 2 files changed, 30 insertions(+), 7 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/pr107411.C

diff --git a/gcc/testsuite/g++.dg/pr107411.C b/gcc/testsuite/g++.dg/pr107411.C
new file mode 100644
index 00000000000..7eefecae4f3
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr107411.C
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-Werror=uninitialized -ftrivial-auto-var-init=zero"  } */
+int t();
+void f(int);
+
+void j()
+{
+  const int& e = t();
+  f(e);
+}
diff --git a/gcc/tree-ssa-uninit.cc b/gcc/tree-ssa-uninit.cc
index c555cf5cd50..b4218900f66 100644
--- a/gcc/tree-ssa-uninit.cc
+++ b/gcc/tree-ssa-uninit.cc
@@ -224,8 +224,6 @@ warn_uninit (opt_code opt, tree t, tree var, gimple *context,
 	     at alt_reloc = temp.
 	  */
 	  tree lhs_var = NULL_TREE;
-	  tree lhs_var_name = NULL_TREE;
-	  const char *lhs_var_name_str = NULL;
 
 	  /* Get the variable name from the 3rd argument of call.  */
 	  tree var_name = gimple_call_arg (var_def_stmt, 2);
@@ -239,11 +237,26 @@ warn_uninit (opt_code opt, tree t, tree var, gimple *context,
 	      else if (TREE_CODE (gimple_assign_lhs (context)) == SSA_NAME)
 		lhs_var = SSA_NAME_VAR (gimple_assign_lhs (context));
 	    }
-	  if (lhs_var
-	      && (lhs_var_name = DECL_NAME (lhs_var))
-	      && (lhs_var_name_str = IDENTIFIER_POINTER (lhs_var_name))
-	      && (strcmp (lhs_var_name_str, var_name_str) == 0))
-	    return;
+	  if (lhs_var)
+	    {
+	      /* Get the name string for the LHS_VAR.
+		 Refer to routine gimple_add_init_for_auto_var.  */
+	      if (DECL_NAME (lhs_var)
+		  && (strcmp (IDENTIFIER_POINTER (DECL_NAME (lhs_var)),
+		      var_name_str) == 0))
+		return;
+	      else if (!DECL_NAME (lhs_var))
+		{
+		  char *lhs_var_name_str
+		    = xasprintf ("D.%u", DECL_UID (lhs_var));
+		  if (strcmp (lhs_var_name_str, var_name_str) == 0)
+		    {
+		      free (lhs_var_name_str);
+		      return;
+		    }
+		  free (lhs_var_name_str);
+		}
+	    }
 	  gcc_assert (var_name_str && var_def_stmt);
 	}
     }
-- 
2.31.1