Re: PING [PATCH][gcc][PR94230]provide an option to change the size limitation for -Wmisleading-indent

[Richard Sandiford <richard.sandiford@arm.com>]

Qing Zhao via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
> Hi,
>
> Please take a look at the attached patch and let me know your comments.
>
> Thanks.
>
> Qing

Acting as a reviewer of last resort since this isn't really my area,
but FWIW, I agree losing column tracking at the current limit is a
genuine regression and should be fixed for GCC 10.

> gcc/ChangeLog:
>
> 2020-04-03  qing zhao  <qing.zhao@oracle.com>
>

Please add:

	PR c/94230

> 	* common.opt: Add -flocation-ranges.
> 	* doc/invoke.texi: Document it.
> 	* toplev.c (process_options): set line_table->default_range_bits
> 	to 0 when flag_location_ranges is false. 

I think it would be worth adding a hint to use the new option to
get_visual_column, when warning about column tracking being disabled.
This should probably be a second inform(), immediately after the
current one.

> @@ -14151,6 +14151,13 @@ This option may be useful in conjunction with the @option{-B} or
>  perform additional processing of the program source between
>  normal preprocessing and compilation.
> 
> +@item -flocation-ranges
> +@opindex flocation-ranges

Normally the documented option should be the non-default one,
so -fno-... in this case.

> +Enable range tracking when recording source locations.
> +By default, GCC enables range tracking when recording source locations.
> +If disable range tracking by -fno-location-ranges, more location space
> +will be saved for column tracking.

My understanding is that the patch doesn't actually disable location-range
tracking, but simply uses a less efficient form for *all* ranges, rather
than only using the less efficient form for ranges that aren't "caret at
start, length < 64 chars".

I know you're simply following the suggestion in the PR, sorry,
but I wonder if the option should instead be:

-flarge-source-files

since that seems like a more user-facing concept.  The option would
tell GCC that the source files are likely to be very large and that
GCC should adapt accordingly.  In particular, the option makes GCC
cope with more source lines at the expense of slowing down compilation
and using more memory.

Thanks,
Richard