Re: [PATCH] PR preprocessor/69177 and PR c++/68819: libcpp fallbacks and -Wmisleading-indentation (v2)

[Jeff Law]

On 01/08/2016 02:40 PM, David Malcolm wrote:

Jakub had some concern about the use of sorry, so here's a revised
version of the patch, with the following changes:
   - fixed the comment issues noted above.

   - changed from a "sorry" to an "inform" (as per Jakub), passing
     in the pertinent location_t to avoid adding a use of
     input_location.

   - I filed PR preprocessor/69177 to cover the increased chance of
     hitting LINE_MAP_MAX_LOCATION_WITH_COLS, so I've updated the
     ChangeLog to reflect which parts affect that, and which just affect
     -Wmisleading-indentation (PR c++/68819).

    This patch resolves both; the test cases are written from the POV
    of specific ranges of location_t values and hence mingle the two PRs
    somewhat.

I did some crude performance testing on this on gimple-match.o;
the compile time taken was < 1% difference with/without this patch
(and that with the patch it had compiled lines 35769-52607 of that
file using the "don't use bit-packing for ranges" fallback).

Successfully bootstrapped&regrtested on x86_64-pc-linux-gnu; adds
11 PASS results to gcc.sum.

OK for trunk?

gcc/c-family/ChangeLog:
        PR c++/68819
        * c-indentation.c (get_visual_column): Add location_t param.
        Handle the columnnumber being zero by effectively disabling the
        warning, with an "inform".
        (should_warn_for_misleading_indentation): Add location_t argument
        for all uses of get_visual_column.

gcc/testsuite/ChangeLog:
        PR c++/68819
        PR preprocessor/69177
        * gcc.dg/plugin/location-overflow-test-1.c: New test case.
        * gcc.dg/plugin/location-overflow-test-2.c: New test case.
        * gcc.dg/plugin/location_overflow_plugin.c: New test plugin.
        * gcc.dg/plugin/plugin.exp (plugin_test_list): Add the above.

libcpp/ChangeLog:
        PR preprocessor/69177
        * line-map.c (LINE_MAP_MAX_LOCATION_WITH_PACKED_RANGES): New
        constant.
        (LINE_MAP_MAX_LOCATION_WITH_COLS): Add note about unit tests
        to comment.
        (can_be_stored_compactly_p): Reduce threshold from
        LINE_MAP_MAX_LOCATION_WITH_COLS to
        LINE_MAP_MAX_LOCATION_WITH_PACKED_RANGES.
        (get_combined_adhoc_loc): Likewise.
        (get_range_from_loc): Likewise.
        (linemap_line_start): Ensure that a new ordinary map is created
        when transitioning from range-packing being enabled to disabled,
        at the LINE_MAP_MAX_LOCATION_WITH_PACKED_RANGES threshold.  Set
        range_bits to 0 for new ordinary maps when beyond this limit.
        Prevent the "increase the column bits of a freshly created map"
        optimization if the range bits has reduced.

OK.
jeff