[RFC PATCH] avoid printing type suffix with %E (PR c/78165)

[Jeff Law]

On 11/19/2016 02:04 PM, Martin Sebor wrote:
> On 10/26/2016 02:46 PM, Joseph Myers wrote:
>> On Wed, 26 Oct 2016, Martin Sebor wrote:
>>
>>> The attached patch implements one such approach by having the pretty
>>> printer recognize the space format flag to suppress the type suffix,
>>> so "%E" still prints the suffix but "% E" does not.  I did this to
>>> preserve the existing output but I think it would be nicer to avoid
>>> printing the suffix with %E and treat (for instance) the pound sign
>>> as a request to add the suffix.  I have tested the attached patch
>>> but not the alternative.
>>
>> I think printing the suffixes is a relic of %E being used to print full
>> expressions.
>>
>> It's established by now that printing expressions reconstructed from
>> trees
>> is a bad idea; we can get better results by having precise location
>> ranges
>> and underlining the relevant part of the source.  So if we could make
>> sure
>> nowhere is trying the use %E (or %qE, etc.) with expressions that might
>> not be constants, where the type might be relevant, then we'd have
>> confidence that stopping printing the suffix is safe.  But given the low
>> quality of the reconstructed expressions, it's probably safe anyway.
>>
>> (Most %qE uses are for identifiers not expressions.  If we give
>> identifiers a different static type from "tree" - and certainly there
>> isn't much reason for them to have the same type as expressions - then
>> we'll need to change the format for either identifiers or expressions.)
>
> Attached is a trivial patch to remove the suffix.  I didn't see
> any failures in the test suite as a result.  I didn't attempt to
> remove the type suffix from any tests (nor did my relatively
> superficial search find any) but it will help simplify the tests
> for my patches that are still in the review queue.
>
> I should add to the rationale for the change I gave in my reply
> to Jeff:
>
>   https://gcc.gnu.org/ml/gcc-patches/2016-11/msg01692.html
>
> that the print_dec[su] function that's sometimes used to format
> integers in warning messages (e.g., by the -Walloca-larger-than
> pass) doesn't add the suffix because it doesn't have knowledge
> of the argument's type (it operates on wide_int).  That further
> adds to the inconsistency in diagnostics.  This patch makes all
> integers in diagnostics consistent regardless of their type.
>
> Thanks
> Martin
>
> gcc-78165.diff
>
>
> PR c/78165 - avoid printing type suffix for constants in %E output
>
> gcc/c-family/ChangeLog:
>
> 	PR c/78165
> 	* c-pretty-print (pp_c_integer_constant): Avoid formatting type
> 	suffix.
I think you and Joseph have made a practical case for dropping the type 
suffix.

Ok for the trunk.

jeff