[PATCH] PR preprocessor/60723 - missing system-ness marks for macro

[Nicholas Ormrod]

Hello Dodji,


I found time this morning to run your changes through our system. I patched our gcc-4.8.1 with your
latest change, and ran it through our folly testsuite.

One thing that I immediately noticed was that this increased the preprocessed size substantially.
When preprocessing my favorite .cpp file, its .ii grew from 137k lines to 145k, a 5% increase.

All the folly code compiled and ran successfully under the changes.

I looked at some of the preprocessed output. I was pleased to see that consecutive macros that
expanded entirely to system tokens did not insert unnecessary line directives between them. I did,
however, notice that __LINE__ was treated as belonging to the calling file, even when its token
appears in the system file. That is to say:

CODE:

// system macro
#define FOO() sys_token __LINE__ sys_token

// non-system callsite
FOO()

// preprocessed output
# 3 "test.cpp" 3 4
sys_token
# 3 "test.cpp"
3
# 3 "test.cpp" 3 4
sys_token

:CODE

This seems to generalize to other builtin macros, like __FILE__.

Otherwise, the code looks fine. There is only one thing I noticed:

> +	 if (do_line_adjustments
> +	 && !in_pragma
> +	 && !line_marker_emitted
> +	 && print.prev_was_system_token != !!in_system_header_at(loc))
> +	 /* The system-ness of this token is different from the one
> +	 of the previous token. Let's emit a line change to
> +	 mark the new system-ness before we emit the token. */
> +	 line_marker_emitted = do_line_change (pfile, token, loc, false);

This line_marker_emitted assignment is immediately overwritten, two lines below. However, from a
maintainability perspective, this is probably a good assignment to keep.

> cpp_output_token (token, print.outf);
> +	 line_marker_emitted = false;
> }


Thanks for this diff!


Cheers,
Nicholas