Fix sometimes-uninitialized warning in gdbscm_value_address

I am getting this warning with clang:

/home/emaisin/src/binutils-gdb/gdb/guile/scm-value.c:439:11: error: variable 'address' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
      if (res_val != NULL)
          ^~~~~~~~~~~~~~~
/home/emaisin/src/binutils-gdb/gdb/guile/scm-value.c:444:32: note: uninitialized use occurs here
      if (gdbscm_is_exception (address))
                               ^~~~~~~
/home/emaisin/src/binutils-gdb/gdb/guile/scm-value.c:439:7: note: remove the 'if' if its condition is always true
      if (res_val != NULL)
      ^~~~~~~~~~~~~~~~~~~~
/home/emaisin/src/binutils-gdb/gdb/guile/scm-value.c:427:18: note: initialize the variable 'address' to silence this warning
      SCM address;
                 ^
                  = nullptr

We can get rid of it with a small refactoring.  I think it's a bit
cleaner/safer to initialize address with a pessimistic value and assign
it on success.  Then there's no chance of using it uninitialized.  If I
understand correctly, the NULL check on res_val was to check whether
value_addr threw, and that if value_addr returns without throwing, the
result will never be NULL.  If that's true, we can skip the res_val
variable.

Tested by running gdb.guile/*.exp locally.

gdb/ChangeLog:

	* guile/scm-value.c (gdbscm_value_address): Initialize address,
	get rid of res_val.

1 files changed, 2 insertions, 7 deletions

diff --git a/gdb/guile/scm-value.c b/gdb/guile/scm-value.c
index 0dc6630..3732666 100644
--- a/gdb/guile/scm-value.c
+++ b/gdb/guile/scm-value.c
@@ -421,24 +421,19 @@ gdbscm_value_address (SCM self)
 
   if (SCM_UNBNDP (v_smob->address))
     {
-      struct value *res_val = NULL;
       struct cleanup *cleanup
 	= make_cleanup_value_free_to_mark (value_mark ());
-      SCM address;
+      SCM address = SCM_BOOL_F;
 
       TRY
 	{
-	  res_val = value_addr (value);
+	  address = vlscm_scm_from_value (value_addr (value));
 	}
       CATCH (except, RETURN_MASK_ALL)
 	{
-	  address = SCM_BOOL_F;
 	}
       END_CATCH
 
-      if (res_val != NULL)
-	address = vlscm_scm_from_value (res_val);
-
       do_cleanups (cleanup);
 
       if (gdbscm_is_exception (address))