>
>
> On 02/15/2012 06:03 PM, Joseph S. Myers wrote:
>> On Wed, 15 Feb 2012, Christian Bruel wrote:
>>
>>> Removal of this NOP_EXPR if !CAN_HAVE_LOCATION_P fixes the problem.
>>> looks safe from my testing, because the loc is inserted using
>>> 'protected_set_expr_location', whereas no loc for a constant case
>>> doesn't seem to introduce new problems with the debugging information.
>>> But in case I also added a few paranoid gcc_assert.
>>
>> Is it safe to set TREE_NO_WARNING without that check? I'd have thought
>> the check was to avoid setting TREE_NO_WARNING on a shared node when
>> warnings are to be disabled in only one context where that node is used.
In fact, we can't omit the TREE_NO_WARNING is !CAN_HAVE_LOCATION_P, the
tentative bellow causes a regression on middle-end/13325.
What I'm unsure is why we couldn't have a TREE_NO_WARNING on a
!CAN_HAVE_LOCATION_P. This seems necessary on some cases without using a
NOP_EXPR.
>>
>
> OK, I see, we can still keep the check, like with :
>
> Index: c-common.c
> ===================================================================
> --- c-common.c (revision 184301)
> +++ c-common.c (working copy)
> @@ -1435,12 +1435,9 @@
> have been done by this point, so remove them again. */
> nowarning |= TREE_NO_WARNING (ret);
> STRIP_TYPE_NOPS (ret);
> - if (nowarning && !TREE_NO_WARNING (ret))
> - {
> - if (!CAN_HAVE_LOCATION_P (ret))
> - ret = build1 (NOP_EXPR, TREE_TYPE (ret), ret);
> - TREE_NO_WARNING (ret) = 1;
> - }
> + if (nowarning && CAN_HAVE_LOCATION_P (ret))
> + TREE_NO_WARNING (ret) = 1;
> +
> if (ret != expr)
> protected_set_expr_location (ret, loc);
> return ret;
>
> We propagate the flag to the new node for non-constant folded
> expressions, or for a converted constant (so NOT_EXPR is not stripped),
>
> Does it make sense to set TREE_NO_WARNING for a not-converted folded
> constant ? it seems that in the proposal, a warning before the fold is
> OK, and a warning after the fold on the new expression is still to be
> honored. The NO_WARNING flag on an non-converted constant that is folded
> looks unnecessary. I tried to forge different scenarios, were the result
> of the folded constant would force a duplicate warning, but no success
> to find a regression case.
>
> Thanks
>
> Christian
