Fixing PR107411

This is the 2nd version of the patch.
compared to the first version, the major change is:

use sprintf to replace xasprintf per Jacub's suggestion.

bootstrapped and regression tested on both x86 and aarch64.

Okay for committing?

thanks.

Qing

=======================

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")

	PR middle-end/107411

gcc/ChangeLog:

	PR middle-end/107411
	* gimplify.cc (gimple_add_init_for_auto_var): Use sprintf to replace
	xasprintf.
	* 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/gimplify.cc

@@ -1775,9 +1775,9 @@ gimple_add_init_for_auto_var (tree decl,
 
   else
     {
-      char *decl_name_anonymous = xasprintf ("D.%u", DECL_UID (decl));
+      char decl_name_anonymous[3 + (HOST_BITS_PER_INT + 2) / 3];
+      sprintf (decl_name_anonymous, "D.%u", DECL_UID (decl));
       decl_name = build_string_literal (decl_name_anonymous);
-      free (decl_name_anonymous);
     }
 
   tree call = build_call_expr_internal_loc (loc, IFN_DEFERRED_INIT,

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);
+}

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 +237,22 @@ 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_buf[3 + (HOST_BITS_PER_INT + 2) / 3];
+		  sprintf (lhs_var_name_str_buf, "D.%u", DECL_UID (lhs_var));
+		  if (strcmp (lhs_var_name_str_buf, var_name_str) == 0)
+		    return;
+		}
+	    }
 	  gcc_assert (var_name_str && var_def_stmt);
 	}
     }