[Bug preprocessor/103026] Implement warning for Unicode bidi override characters [CVE-2021-42574]

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103026

--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by David Malcolm <dmalcolm@gcc.gnu.org>:

https://gcc.gnu.org/g:bef32d4a28595e933f24fef378cf052a30b674a7

commit r12-5356-gbef32d4a28595e933f24fef378cf052a30b674a7
Author: David Malcolm <dmalcolm@redhat.com>
Date:   Tue Nov 2 15:45:22 2021 -0400

    libcpp: capture and underline ranges in -Wbidi-chars= [PR103026]

    This patch converts the bidi::vec to use a struct so that we can
    capture location_t values for the bidirectional control characters.

    Before:

      Wbidi-chars-1.c: In function âmainâ:
      Wbidi-chars-1.c:6:43: warning: unpaired UTF-8 bidirectional control
character detected [-Wbidi-chars=]
          6 |     /*<U+202E> } <U+2066>if (isAdmin)<U+2069> <U+2066> begin
admins only */
            |                                                                  
        ^
      Wbidi-chars-1.c:9:28: warning: unpaired UTF-8 bidirectional control
character detected [-Wbidi-chars=]
          9 |     /* end admins only <U+202E> { <U+2066>*/
            |                                            ^

    After:

      Wbidi-chars-1.c: In function âmainâ:
      Wbidi-chars-1.c:6:43: warning: unpaired UTF-8 bidirectional control
characters detected [-Wbidi-chars=]
          6 |     /*<U+202E> } <U+2066>if (isAdmin)<U+2069> <U+2066> begin
admins only */
            |       ~~~~~~~~                                ~~~~~~~~           
        ^
            |       |                                       |                  
        |
            |       |                                       |                  
        end of bidirectional context
            |       U+202E (RIGHT-TO-LEFT OVERRIDE)         U+2066
(LEFT-TO-RIGHT ISOLATE)
      Wbidi-chars-1.c:9:28: warning: unpaired UTF-8 bidirectional control
characters detected [-Wbidi-chars=]
          9 |     /* end admins only <U+202E> { <U+2066>*/
            |                        ~~~~~~~~   ~~~~~~~~ ^
            |                        |          |        |
            |                        |          |        end of bidirectional
context
            |                        |          U+2066 (LEFT-TO-RIGHT ISOLATE)
            |                        U+202E (RIGHT-TO-LEFT OVERRIDE)

    Signed-off-by: David Malcolm <dmalcolm@redhat.com>

    gcc/testsuite/ChangeLog:
            PR preprocessor/103026
            * c-c++-common/Wbidi-chars-ranges.c: New test.

    libcpp/ChangeLog:
            PR preprocessor/103026
            * lex.c (struct bidi::context): New.
            (bidi::vec): Convert to a vec of context rather than unsigned
            char.
            (bidi::ctx_at): Rename to...
            (bidi::pop_kind_at): ...this and reimplement for above change.
            (bidi::current_ctx): Update for change to vec.
            (bidi::current_ctx_ucn_p): Likewise.
            (bidi::current_ctx_loc): New.
            (bidi::on_char): Update for usage of context struct.  Add "loc"
            param and pass it when pushing contexts.
            (get_location_for_byte_range_in_cur_line): New.
            (get_bidi_utf8): Rename to...
            (get_bidi_utf8_1): ...this, reintroducing...
            (get_bidi_utf8): ...as a wrapper, setting *OUT when the result is
            not NONE.
            (get_bidi_ucn): Rename to...
            (get_bidi_ucn_1): ...this, reintroducing...
            (get_bidi_ucn): ...as a wrapper, setting *OUT when the result is
            not NONE.
            (class unpaired_bidi_rich_location): New.
            (maybe_warn_bidi_on_close): Use unpaired_bidi_rich_location when
            reporting on unpaired bidi chars.  Split into singular vs plural
            spellings.
            (maybe_warn_bidi_on_char): Pass in a location_t rather than a
            const uchar * and use it when emitting warnings, and when calling
            bidi::on_char.
            (_cpp_skip_block_comment): Capture location when kind is not NONE
            and pass it to maybe_warn_bidi_on_char.
            (skip_line_comment): Likewise.
            (forms_identifier_p): Likewise.
            (lex_raw_string): Likewise.
            (lex_string): Likewise.

    Signed-off-by: David Malcolm <dmalcolm@redhat.com>