[gcc r13-6379] Fixing PR107411

[gcc r13-6379] Fixing PR107411

[Qing Zhao]

https://gcc.gnu.org/g:afe6cea4489846aa8585f3c045d16cdaa08cc6cd

commit r13-6379-gafe6cea4489846aa8585f3c045d16cdaa08cc6cd
Author: Qing Zhao <qing.zhao@oracle.com>
Date:   Tue Feb 28 17:11:05 2023 +0000

    Fixing PR107411
    
    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.

Diff:
---
 gcc/gimplify.cc                 |  4 ++--
 gcc/testsuite/g++.dg/pr107411.C | 10 ++++++++++
 gcc/tree-ssa-uninit.cc          | 23 ++++++++++++++++-------
 3 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc
index 96845154a92..35d1ea22623 100644
--- a/gcc/gimplify.cc
+++ b/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,
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..9f720ae1f4f 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 +237,22 @@ 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);
 	}
     }