[Bug pch/71934] pch cannot be disabled so gcc cannot be position independent

[cvs-commit at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71934

--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>:

https://gcc.gnu.org/g:fe7c3ecff1f9c0520090a77fa824d8c5d9dbec12

commit r12-5768-gfe7c3ecff1f9c0520090a77fa824d8c5d9dbec12
Author: Jakub Jelinek <ja...@redhat.com>
Date:   Fri Dec 3 11:03:30 2021 +0100

    pch: Add support for PCH for relocatable executables [PR71934]

    So, if we want to make PCH work for PIEs, I'd say we can:
    1) add a new GTY option, say callback, which would act like
       skip for non-PCH and for PCH would make us skip it but
       remember for address bias translation
    2) drop the skip for tree_translation_unit_decl::language
    3) change get_unnamed_section to have const char * as
       last argument instead of const void *, change
       unnamed_section::data also to const char * and update
       everything related to that
    4) maybe add a host hook whether it is ok to support binaries
       changing addresses (the only thing I'm worried is if
       some host that uses function descriptors allocates them
       dynamically instead of having them somewhere in the
       executable)
    5) maybe add a gengtype warning if it sees in GTY tracked
       structure a function pointer without that new callback
       option

    Here is 1), 2), 3) implemented.

    Note, on stdc++.h.gch/O2g.gch there are just those 10 relocations without
    the second patch, with it a few more, but nothing huge.  And for non-PIEs
    there isn't really any extra work on the load side except freading two
scalar
    values and fseek.

    2021-12-03  Jakub Jelinek  <ja...@redhat.com>

            PR pch/71934
    gcc/
            * ggc.h (gt_pch_note_callback): Declare.
            * gengtype.h (enum typekind): Add TYPE_CALLBACK.
            (callback_type): Declare.
            * gengtype.c (dbgprint_count_type_at): Handle TYPE_CALLBACK.
            (callback_type): New variable.
            (process_gc_options): Add CALLBACK argument, handle callback
            option.
            (set_gc_used_type): Adjust process_gc_options caller, if callback,
            set type to &callback_type.
            (output_mangled_typename): Handle TYPE_CALLBACK.
            (walk_type): Likewise.  Handle callback option.
            (write_types_process_field): Handle TYPE_CALLBACK.
            (write_types_local_user_process_field): Likewise.
            (write_types_local_process_field): Likewise.
            (write_root): Likewise.
            (dump_typekind): Likewise.
            (dump_type): Likewise.
            * gengtype-state.c (type_lineloc): Handle TYPE_CALLBACK.
            (state_writer::write_state_callback_type): New method.
            (state_writer::write_state_type): Handle TYPE_CALLBACK.
            (read_state_callback_type): New function.
            (read_state_type): Handle TYPE_CALLBACK.
            * ggc-common.c (callback_vec): New variable.
            (gt_pch_note_callback): New function.
            (gt_pch_save): Stream out gt_pch_save function address and
relocation
            table.
            (gt_pch_restore): Stream in saved gt_pch_save function address and
            relocation table and apply relocations if needed.
            * doc/gty.texi (callback): Document new GTY option.
            * varasm.c (get_unnamed_section): Change callback argument's type
and
            last argument's type from const void * to const char *.
            (output_section_asm_op): Change argument's type from const void *
            to const char *, remove unnecessary cast.
            * tree-core.h (struct tree_translation_unit_decl): Drop GTY((skip))
            from language member.
            * output.h (unnamed_section_callback): Change argument type from
            const void * to const char *.
            (struct unnamed_section): Use GTY((callback)) instead of
GTY((skip))
            for callback member.  Change data member type from const void *
            to const char *.
            (struct noswitch_section): Use GTY((callback)) instead of
GTY((skip))
            for callback member.
            (get_unnamed_section): Change callback argument's type and
            last argument's type from const void * to const char *.
            (output_section_asm_op): Change argument's type from const void *
            to const char *.
            * config/avr/avr.c (avr_output_progmem_section_asm_op): Likewise.
            Remove unneeded cast.
            * config/darwin.c (output_objc_section_asm_op): Change argument's
type
            from const void * to const char *.
            * config/pa/pa.c (som_output_text_section_asm_op): Likewise.
            (som_output_comdat_data_section_asm_op): Likewise.
            * config/rs6000/rs6000.c (rs6000_elf_output_toc_section_asm_op):
            Likewise.
            (rs6000_xcoff_output_readonly_section_asm_op): Likewise.  Instead
            of dereferencing directive hardcode variable names and decide based
on
            whether directive is NULL or not.
            (rs6000_xcoff_output_readwrite_section_asm_op): Change argument's
type
            from const void * to const char *.
            (rs6000_xcoff_output_tls_section_asm_op): Likewise.  Instead
            of dereferencing directive hardcode variable names and decide based
on
            whether directive is NULL or not.
            (rs6000_xcoff_output_toc_section_asm_op): Change argument's type
            from const void * to const char *.
            (rs6000_xcoff_asm_init_sections): Adjust get_unnamed_section
callers.
    gcc/c-family/
            * c-pch.c (struct c_pch_validity): Remove pch_init member.
            (pch_init): Don't initialize v.pch_init.
            (c_common_valid_pch): Don't warn and punt if .text addresses
change.
    libcpp/
            * include/line-map.h (class line_maps): Add GTY((callback)) to
            reallocator and round_alloc_size members.