[Bug c/40635] bogus name and location in 'may be used uninitialized' warning

[manu at gcc dot gnu dot org]

------- Comment #2 from manu at gcc dot gnu dot org  2009-07-06 13:19 -------
The root cause is a combination of inline and copy-rename. Copy rename has the
following code:

  /* Never attempt to coalesce 2 user variables unless one is an inline
     variable.  */
  if (!ign1 && !ign2)
    {
      if (DECL_FROM_INLINE (root2))
        ign2 = true;
      else if (DECL_FROM_INLINE (root1))
        ign1 = true;
      else
        {
          if (debug)
            fprintf (debug, " : 2 different USER vars. No coalesce.\n");
          return false;
        }
    }

  /* If both values have default defs, we can't coalesce.  If only one has a
     tag, make sure that variable is the new root partition.  */
  if (gimple_default_def (cfun, root1))
    {
      if (gimple_default_def (cfun, root2))
        {
          if (debug)
            fprintf (debug, " : 2 default defs. No coalesce.\n");
          return false;
        }
      else
        {
          ign2 = true;
          ign1 = false;
        }
    }
  else if (gimple_default_def (cfun, root2))
    {
      ign1 = true;
      ign2 = false;
    }

The net result is that when it combines sockt_rd with s42, it favours s42. This
is the reason it prints s42. However, the location printed corresponds to the
statement:

 if (sockt_rd < 0)
        return -1;



Then, warn_uninit is not able to detect that this comes from some inlined
thing. If we do this:

-  location = (context != NULL && gimple_has_location (context))
+  location = (!DECL_FROM_INLINE (var) && context != NULL
+             && gimple_has_location (context))
             ? gimple_location (context)
-            : DECL_SOURCE_LOCATION (var);
+            : DECL_SOURCE_LOCATION (DECL_ORIGIN (var));

Then we get the right location (line, column) but still the wrong function. I
am not sure how to force the diagnostics machinery to display the correct
function.


-- 

manu at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |manu at gcc dot gnu dot org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2009-07-06 13:19:06
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40635