Re: [RFC/RFA] gdb.cp/classes.exp: Don't try to print local variable out of scope

[Corinna Vinschen <vinschen@redhat.com>]

Hi Michael,

On Mar  9 10:11, Michael Elizabeth Chastain wrote:
> That is: is a local variable required to exist at the closing brace of a
> function?
> 
> I think your answer is "no, it's not required to exist, therefore the
> gdb test suite should change".  My answer is "reluctantly, no,
> it's not required to exist"; I don't think the famous gcc -O0
> debug info clause covers this case.  I'm curious what drow and
> carlton and other people have to say.

basically this problem is similar to the "having the same variable
defined twice in a function" problem:

  1 void foo ()
  2 {
  3   int i = 1;
  4   {
  5     int i = 2;
  6     bar(i);
  7   }
  8   bar (i);
  9 }

Is line 7 still in the scope of the inner definition of variable `i'?
Which `i' should be printed at that point?

>   void foo ()
>   {
>     int i;
>     i = 1;
>     bar (i);
>   }
> 
>   (gdb) break bar
>   (gdb) run
>   (gdb) finish
>   (gdb) print i
> 
> Is it okay for gcc to emit debug info that "i" is out of scope here?

IMHO yes.  Keep in mind that it's a *local* variable.  It's practically
dead at this point.  $pc sits already in the epilogue which destroys the
variable anyway.  Just one `stepi' would perhaps *really* destroy the
variable and GDB might print some entirely confused value.

> cv> I'd suggest to change the testsuite case to add another line to the
> cv> function enums1(), so that it's sure to be still in the scope of the
> cv> local variable obj_with_enum.
> 
> misc.cc is used by three *.exp files so I do not want to touch it
> at all, so I am dis-approving your patch.  I will write a patch to
> remove the "gdb_test next" in test_enums instead.

I tested the whole gdb.cp testsuite on linux-x-sh with and without the
patch and the only difference in the testsuite output where the tests
directly affected by this change:

  7c7,10
  < (gdb) KFAIL: gdb.cp/classes.exp: ptype obj_with_enum (PRMS: gdb/57)
  ---
  > (gdb) FAIL: gdb.cp/classes.exp: print obj_with_enum (2)
  > (gdb) FAIL: gdb.cp/classes.exp: print obj_with_enum.priv_enum
  > (gdb) FAIL: gdb.cp/classes.exp: ptype obj_with_enum.priv_enum
  > (gdb) FAIL: gdb.cp/classes.exp: ptype obj_with_enum


Corinna

-- 
Corinna Vinschen
Cygwin Developer
Red Hat, Inc.