Re: [Version 2][PATCH][gcc][PR94230]provide an option to change the size limitation for -Wmisleading-indent

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

Qing Zhao <QING.ZHAO@ORACLE.COM> writes:
> ---
>  gcc/c-family/c-indentation.c                           |  3 +++
>  gcc/common.opt                                         |  5 +++++
>  gcc/doc/invoke.texi                                    | 15 ++++++++++++++-
>  gcc/testsuite/gcc.dg/plugin/location-overflow-test-1.c |  2 +-
>  gcc/toplev.c                                           |  3 +++
>  5 files changed, 26 insertions(+), 2 deletions(-)
>
> diff --git a/gcc/c-family/c-indentation.c b/gcc/c-family/c-indentation.c
> index f737555..7074b10 100644
> --- a/gcc/c-family/c-indentation.c
> +++ b/gcc/c-family/c-indentation.c
> @@ -67,6 +67,9 @@ get_visual_column (expanded_location exploc, location_t loc,
>  		  "%<-Wmisleading-indentation%> is disabled from this point"
>  		  " onwards, since column-tracking was disabled due to"
>  		  " the size of the code/headers");
> +	  inform (loc,
> +		  "please add %<-flarge-source-files%> to invoke more" 
> +		  " column-tracking for large source files");
>  	}
>        return false;
>      }

This should be conditional on !flag_large_source_files.

> diff --git a/gcc/common.opt b/gcc/common.opt
> index 4368910..10a3d5b 100644
> --- a/gcc/common.opt
> +++ b/gcc/common.opt
> @@ -1597,6 +1597,11 @@ fkeep-gc-roots-live
>  Common Undocumented Report Var(flag_keep_gc_roots_live) Optimization
>  ; Always keep a pointer to a live memory block
>  
> +flarge-source-files
> +Common Report Var(flag_large_source_files) Init(0)
> +Adjust GCC to cope with large source files to provide more accurate
> +column information.
> +

I'm having difficulty suggesting wording here, but I think would be good
to mention the downside.  How about:

----------------------
Improve GCC's ability to track column numbers in large source files,
at the expense of slower compilation.
----------------------

>  floop-parallelize-all
>  Common Report Var(flag_loop_parallelize_all) Optimization
>  Mark all loops as parallel.
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 96a9516..c6ea9ef 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -574,7 +574,7 @@ Objective-C and Objective-C++ Dialects}.
>  -fdebug-cpp  -fdirectives-only  -fdollars-in-identifiers  @gol
>  -fexec-charset=@var{charset}  -fextended-identifiers  @gol
>  -finput-charset=@var{charset}  -fmacro-prefix-map=@var{old}=@var{new}  @gol
> --fmax-include-depth=@var{depth} @gol
> +-fmax-include-depth=@var{depth} -flarge-source-files @gol
>  -fno-canonical-system-headers  -fpch-deps  -fpch-preprocess  @gol
>  -fpreprocessed  -ftabstop=@var{width}  -ftrack-macro-expansion  @gol
>  -fwide-exec-charset=@var{charset}  -fworking-directory @gol

This should be kept in alphabetical order, so after -finput-charset.

> @@ -14151,6 +14151,19 @@ 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 -flarge-source-files
> +@opindex flarge-source-files
> +Adjust GCC to cope with large source files to provide more accurate
> +column information. 
> +By default, GCC will lose accurate column information if the source 
> +file is very large.
> +If this option is provided, GCC will adapt accordingly to provide more
> +accurate column information. 
> +This option may be useful when any user hits the @option{-Wmisleading-indent} 
> +note, "is disabled from this point onwards, since column-tracking was disabled 
> +due to the size of the code/headers", or hits the limit at which columns get
> +dropped from diagnostics.
> +

On a similar vein, how about:

----------------------
Adjust GCC to expect large source files, at the expense of slower
compilation and higher memory usage.

Specifically, GCC normally tracks both column numbers and line numbers
within source files and it normally prints both of these numbers in
diagnostics.  However, once it has processed a certain number of source
lines, it stops tracking column numbers and only tracks line numbers.
This means that diagnostics for later lines do not include column numbers.
It also means that options like @option{-Wmisleading-indent} cease to work
at that point, although the compiler prints a note if this happens.
Passing @option{-flarge-source-files} significantly increases the number
of source lines that GCC can process before it stops tracking column
numbers.
----------------------

Thanks,
Richard