PR c++/77949 identifies an ICE when the C++ frontend attempts to emit a
fix-it hint inserting a missing semicolon at column 4097 of a source file.
This column value exceeds LINE_MAP_MAX_COLUMN_NUMBER and hence isn't
representable using a location_t.
Attempting to do so leads to these problems, which this patch fixes:
(a) when encountering a column number > LINE_MAP_MAX_COLUMN_NUMBER we
create a new linemap with m_column_and_range_bits == 0, but
linemap_position_for_column doesn't check for this, and hence can emit
a bogus location_t value that's calculated relative to the previous
linemap start, but which will be decoded relative to the new linemap,
leading to very large incorrect line values.
(b) when encountering a column number that can't be represented, and
for which the linemap was pre-existing, the code would hit this assertion:
if (linemap_assert_fails (column < (1u << map->m_column_and_range_bits)))
around a bail-out condition. The patch replaces this assertion with a
simple conditional, to stop the ICE when this occurs, and fixes the
bit count (effective column bits, vs column+range bits)
(c) the C++ frontend wasn't checking for failure of
linemap_position_for_loc_and_offset when considering emitting the fix-it
hint. The patch adds a conditional, so that no fix-it hint is emitted
if the location is bogus.
gcc/cp/ChangeLog:
PR c++/77949
* parser.c (cp_parser_class_specifier_1): Only suggest inserting
a missing semicolon if we have a valid insertion location for
the fix-it hint.
gcc/ChangeLog:
PR c++/77949
* input.c (selftest::test_accessing_ordinary_linemaps): Verify
that we correctly handle column numbers greater than
LINE_MAP_MAX_COLUMN_NUMBER.
gcc/testsuite/ChangeLog:
PR c++/77949
* g++.dg/diagnostic/pr77949.C: New test case.
libcpp/ChangeLog:
PR c++/77949
* line-map.c (linemap_position_for_column): When calling
linemap_start_line, detect if a new linemap was created with
0 column bits, and bail out early if this is the case.
(linemap_position_for_loc_and_offset): Replace overzealous
linemap_assert_fails with a simple conditional; use correct
bit count.
From-SVN: r244292
b9f4757f8e