[patch] Fix thinko in libcpp preparation patch for modules

[Eric Botcazou]

Hi,

this is a regression present on the mainline, 10 and 9 branches introduced by 
a preparation patch for modules applied to libcpp a while ago by Nathan:

2018-10-31  Nathan Sidwell  <nathan@acm.org>

	* include/line-map.h (IS_ORDINARY_LOC, IS_MACRO_LOC): New
	predicates.
	(IS_ADHOC_LOC): Move earlier.
	(MAP_ORDINARY_P): Use IS_ORDINARY_LOC.
	* line-map.c (linemap_location_from_macro_expansion_p): Use
	IS_MACRO_LOC.

The problem is that the new IS_MACRO_LOC macro:

inline bool
IS_MACRO_LOC (location_t loc)
{
  return !IS_ORDINARY_LOC (loc) && !IS_ADHOC_LOC (loc);
}

is not fully correct since the position of the macro lines is not fixed:

/* Returns the lowest location [of a token resulting from macro
   expansion] encoded in this line table.  */
inline location_t
LINEMAPS_MACRO_LOWEST_LOCATION (const line_maps *set)
{
  return LINEMAPS_MACRO_USED (set)
         ? MAP_START_LOCATION (LINEMAPS_LAST_MACRO_MAP (set))
         : MAX_LOCATION_T + 1;
}

In Ada, LINEMAPS_MACRO_USED is false so LINEMAPS_MACRO_LOWEST_LOCATION is 
MAX_LOCATION_T + 1, but IS_MACRO_LOC nevertheless returns true for anything in 
the range [LINE_MAP_MAX_LOCATION; MAX_LOCATION_T], thus yielding an ICE in 
linemap_macro_map_lookup for very large files:

  linemap_assert (line >= LINEMAPS_MACRO_LOWEST_LOCATION (set));

during GIMPLE pass: lower
in linemap_macro_map_lookup, at libcpp/line-map.c:1080during GIMPLE pass: 
lower
in linemap_macro_map_lookup, at libcpp/line-map.c:1080Internal compiler error: 
Error reporting routines re-entered.
0x210b2bf linemap_macro_map_lookup
        /home/eric/cvs/gcc/libcpp/line-map.c:1080
0x210b2bf linemap_lookup(line_maps const*, unsigned int)
        /home/eric/cvs/gcc/libcpp/line-map.c:1020
0x210b436 linemap_macro_loc_to_exp_point
        /home/eric/cvs/gcc/libcpp/line-map.c:1560
0x20e5b55 expand_location_1
        /home/eric/cvs/gcc/gcc/input.c:190
0x20e6f90 expand_location(unsigned int)
        /home/eric/cvs/gcc/gcc/input.c:809
0xb48119 internal_error_function
        /home/eric/cvs/gcc/gcc/ada/gcc-interface/misc.c:339
0x20c5108 diagnostic_report_diagnostic(diagnostic_context*, diagnostic_info*)
        /home/eric/cvs/gcc/gcc/diagnostic.c:1225
0x20c56ff diagnostic_impl
        /home/eric/cvs/gcc/gcc/diagnostic.c:1406
0x20c6087 internal_error(char const*, ...)
        /home/eric/cvs/gcc/gcc/diagnostic.c:1808
0xb1d217 fancy_abort(char const*, int, char const*)
        /home/eric/cvs/gcc/gcc/diagnostic.c:1907
0x210b2bf linemap_macro_map_lookup
        /home/eric/cvs/gcc/libcpp/line-map.c:1080
0x210b2bf linemap_lookup(line_maps const*, unsigned int)
        /home/eric/cvs/gcc/libcpp/line-map.c:1020
0x210b436 linemap_macro_loc_to_exp_point
        /home/eric/cvs/gcc/libcpp/line-map.c:1560
0x20e5b55 expand_location_1
        /home/eric/cvs/gcc/gcc/input.c:190
0x20e6f90 expand_location(unsigned int)
        /home/eric/cvs/gcc/gcc/input.c:809
0xb48119 internal_error_function
        /home/eric/cvs/gcc/gcc/ada/gcc-interface/misc.c:339
0x20c5108 diagnostic_report_diagnostic(diagnostic_context*, diagnostic_info*)
        /home/eric/cvs/gcc/gcc/diagnostic.c:1225
0x20c56ff diagnostic_impl
        /home/eric/cvs/gcc/gcc/diagnostic.c:1406
0x20c6087 internal_error(char const*, ...)
        /home/eric/cvs/gcc/gcc/diagnostic.c:1808
0xb1d217 fancy_abort(char const*, int, char const*)
        /home/eric/cvs/gcc/gcc/diagnostic.c:1907
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

The attached fix simply deletes IS_MACRO_LOC and replaces it with the proper 
test, taking into account that IS_ADHOC_LOC has always already been tested.

Tested on x86-64/Linux, OK for mainline, 10 and 9 branches?


2021-03-23  Eric Botcazou  <ebotcazou@adacore.com>

libcpp/
	* include/line-map.h (IS_MACRO_LOC): Delete.
	* line-map.c (linemap_location_from_macro_expansion_p): Test
	against the LINEMAPS_MACRO_LOWEST_LOCATION of the linemap.
gcc/cp/
	* module.cc (ordinary_loc_of): Likewise.
	(module_state::write_location): Likewise.

-- 
Eric Botcazou
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