Fix crashes on dangling display expressions.
* ada-lang.c (ada_operator_check): New function.
(ada_exp_descriptor): Fill-in the field operator_check.
* c-lang.c (exp_descriptor_c): Fill-in the field operator_check.
* jv-lang.c (exp_descriptor_java): Likewise.
* m2-lang.c (exp_descriptor_modula2): Likewise.
* scm-lang.c (exp_descriptor_scm): Likewise.
* parse.c (exp_descriptor_standard): Likewise.
(operator_check_standard): New function.
(exp_iterate, exp_uses_objfile_iter, exp_uses_objfile): New functions.
* parser-defs.h (struct exp_descriptor): New field operator_check.
(operator_check_standard, exp_uses_objfile): New declarations.
* printcmd.c: Remove the inclusion of solib.h.
(display_uses_solib_p): Remove the function.
(clear_dangling_display_expressions): Call lookup_objfile_from_block
and exp_uses_objfile instead of display_uses_solib_p.
* solist.h (struct so_list) <objfile>: New comment.
* symtab.c (lookup_objfile_from_block): Remove the static qualifier.
* symtab.h (lookup_objfile_from_block): New declaration.
(struct general_symbol_info) <obj_section>: Extend the comment.
gdb/testsuite/
Fix crashes on dangling display expressions.
* gdb.base/solib-display.exp: Call gdb_gnu_strip_debug if LIBSEPDEBUG
is SEP.
(lib_flags): Remove the "debug" keyword.
(libsepdebug): New variable for iterating new loop.
(save_pf_prefix): New variable wrapping the loop.
(sep_lib_flags): New variable derived from LIB_FLAGS. Use it.
* lib/gdb.exp (gdb_gnu_strip_debug): Document the return code.
* gdb.base/solib-display.exp: Replace gdb_exit, gdb_start,
gdb_reinitialize_dir and gdb_load by clean_restart. Remove trailing
gdb_exit and return.
(executable): New variable.
(binfile): Use it.
* printcmd.c (do_one_display): Reparse exp_string.
(display_uses_solib_p): New function.
(clear_dangling_display_expressions): New function.
(_initialize_printcmd): Add observer.
* solib.c (no_shared_libraries): Swap order of calls to
clear_solib and objfile_purge_solibs.
