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

Iain Sandoe iain@sandoe.co.uk
Tue Nov 9 08:07:27 GMT 2021



> On 9 Nov 2021, at 07:12, Richard Biener <rguenther@suse.de> wrote:
> 
> On Mon, 8 Nov 2021, Jakub Jelinek wrote:
> 
>> On Mon, Nov 08, 2021 at 12:46:04PM +0100, Jakub Jelinek via Gcc-patches wrote:
>>> 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
>> 
>> So, here is 1), 2), 3) implemented.  With this patch alone,
>> g++.dg/pch/system-2.C test ICEs.  This is because GCC 12 has added
>> function::x_range_query member, which is set to &global_ranges on
>> cfun creation and is:
>>  range_query * GTY ((skip)) x_range_query;
>> which means when a PIE binary writes PCH and a PIE binary loaded
>> at a different address loads it, cfun->x_range_query might be a garbage
>> pointer.  We can either apply a patch like the attached one after
>> this inline patch, but then probably callback is misnamed and we should
>> rename it to relocate_and_skip or something similar.  Or we could
>> e.g. during gimplification overwrite cfun->x_range_query = &global_ranges.
> 
> I think struct function allocation should initialize it to NULL and
> the init to &global_ranges be done only when we do init_tree_ssa?
> In fact x_range_query could be moved to the gimple_df substructure
> to make that clear.
> 
> Hopefully PCH happens before init_tree_ssa.
> 
>> Other than that make check-gcc check-g++ passes RUNTESTFLAGS=pch.exp.
>> 
>> Not really sure about PA or IA-64 function descriptors, are any of those
>> allocated by the dynamic linker rather than created by the static linker?
>> I guess instead of removing the c-pch.c changes we could remember there
>> not just a function pointer, but also a data pointer and compare if both
>> are either the same or have the same load bias and punt only if they
>> have different bias.  Though, on architecture where all function pointers
>> would be dynamically allocated and could change any time even that wouldn't
>> be really a reliable check.
>> 
>> 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.
>> 
>> Thoughts on this?

- thanks for doing it, I still think a working solution is better than a disable.

- This would be a fix for PR 71934

- I applied the patches on Darwin and there’s still some case(s) to find and fix
  cc1/cc1plus hang on pch input, when any diagnostic is emitted (doing some
  linemap lookup) .. hopefully, I can find some time to figure out what is not 
  happy.

> I'm not keen on further life support for PCH, but then if the work is
> done it's hard to reject it...
> 
> Note there might be still platforms not supporting PCH and so Iains
> patches still look useful to me.

Yeah, what would be most useful at this stage is some way to get those
tested against some wider set of package builds to see if anything fires
that breaks stuff.

> I also wonder whether we want to require active marking of types
> with PCH support and assert when PCH write runs into objects without?

anything that makes GTY markup more robust is a Good Idea.
Iain

> 
> Richard.
> 
>> 2021-11-08  Jakub Jelinek  <jakub@redhat.com>
>> 
>> 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.
>> 
>> --- gcc/ggc.h.jj	2021-08-19 11:42:27.366422386 +0200
>> +++ gcc/ggc.h	2021-11-08 16:46:02.604618109 +0100
>> @@ -46,6 +46,10 @@ typedef void (*gt_handle_reorder) (void
>> /* Used by the gt_pch_n_* routines.  Register an object in the hash table.  */
>> extern int gt_pch_note_object (void *, void *, gt_note_pointers);
>> 
>> +/* Used by the gt_pch_p_* routines.  Register address of a callback
>> +   pointer.  */
>> +extern void gt_pch_note_callback (void *, void *);
>> +
>> /* Used by the gt_pch_n_* routines.  Register that an object has a reorder
>>    function.  */
>> extern void gt_pch_note_reorder (void *, void *, gt_handle_reorder);
>> --- gcc/gengtype.h.jj	2021-07-20 10:08:09.892687719 +0200
>> +++ gcc/gengtype.h	2021-11-08 15:19:59.194210185 +0100
>> @@ -154,6 +154,9 @@ enum typekind {
>>   TYPE_UNION,           /* Type for GTY-ed discriminated unions.  */
>>   TYPE_POINTER,         /* Pointer type to GTY-ed type.  */
>>   TYPE_ARRAY,           /* Array of GTY-ed types.  */
>> +  TYPE_CALLBACK,	/* A function pointer that needs relocation if
>> +			   the executable has been loaded at a different
>> +			   address.  */
>>   TYPE_LANG_STRUCT,     /* GCC front-end language specific structs.
>>                            Various languages may have homonymous but
>>                            different structs.  */
>> @@ -331,6 +334,9 @@ extern struct type string_type;
>> extern struct type scalar_nonchar;
>> extern struct type scalar_char;
>> 
>> +/* The one and only TYPE_CALLBACK.  */
>> +extern struct type callback_type;
>> +
>> /* Test if a type is a union, either a plain one or a language
>>    specific one.  */
>> #define UNION_P(x)					\
>> --- gcc/gengtype.c.jj	2021-10-04 10:16:10.885140187 +0200
>> +++ gcc/gengtype.c	2021-11-08 16:30:41.981750183 +0100
>> @@ -172,6 +172,7 @@ dbgprint_count_type_at (const char *fil,
>>   int nb_struct = 0, nb_union = 0, nb_array = 0, nb_pointer = 0;
>>   int nb_lang_struct = 0;
>>   int nb_user_struct = 0, nb_undefined = 0;
>> +  int nb_callback = 0;
>>   type_p p = NULL;
>>   for (p = t; p; p = p->next)
>>     {
>> @@ -202,6 +203,9 @@ dbgprint_count_type_at (const char *fil,
>> 	case TYPE_ARRAY:
>> 	  nb_array++;
>> 	  break;
>> +	case TYPE_CALLBACK:
>> +	  nb_callback++;
>> +	  break;
>> 	case TYPE_LANG_STRUCT:
>> 	  nb_lang_struct++;
>> 	  break;
>> @@ -217,6 +221,8 @@ dbgprint_count_type_at (const char *fil,
>>     fprintf (stderr, "@@%%@@ %d structs, %d unions\n", nb_struct, nb_union);
>>   if (nb_pointer > 0 || nb_array > 0)
>>     fprintf (stderr, "@@%%@@ %d pointers, %d arrays\n", nb_pointer, nb_array);
>> +  if (nb_callback > 0)
>> +    fprintf (stderr, "@@%%@@ %d callbacks\n", nb_callback);
>>   if (nb_lang_struct > 0)
>>     fprintf (stderr, "@@%%@@ %d lang_structs\n", nb_lang_struct);
>>   if (nb_user_struct > 0)
>> @@ -495,6 +501,10 @@ struct type scalar_char = {
>>   TYPE_SCALAR, 0, 0, 0, GC_USED, {0}
>> };
>> 
>> +struct type callback_type = {
>> +  TYPE_CALLBACK, 0, 0, 0, GC_USED, {0}
>> +};
>> +
>> /* Lists of various things.  */
>> 
>> pair_p typedefs = NULL;
>> @@ -1464,7 +1474,7 @@ static void set_gc_used (pair_p);
>> 
>> static void
>> process_gc_options (options_p opt, enum gc_used_enum level, int *maybe_undef,
>> -		    int *length, int *skip, type_p *nested_ptr)
>> +		    int *length, int *skip, int *callback, type_p *nested_ptr)
>> {
>>   options_p o;
>>   for (o = opt; o; o = o->next)
>> @@ -1478,6 +1488,8 @@ process_gc_options (options_p opt, enum
>>       *length = 1;
>>     else if (strcmp (o->name, "skip") == 0)
>>       *skip = 1;
>> +    else if (strcmp (o->name, "callback") == 0)
>> +      *callback = 1;
>>     else if (strcmp (o->name, "nested_ptr") == 0
>> 	     && o->kind == OPTION_NESTED)
>>       *nested_ptr = ((const struct nested_ptr_data *) o->info.nested)->type;
>> @@ -1526,7 +1538,7 @@ set_gc_used_type (type_p t, enum gc_used
>> 	type_p dummy2;
>> 	bool allow_undefined_field_types = (t->kind == TYPE_USER_STRUCT);
>> 
>> -	process_gc_options (t->u.s.opt, level, &dummy, &dummy, &dummy,
>> +	process_gc_options (t->u.s.opt, level, &dummy, &dummy, &dummy, &dummy,
>> 			    &dummy2);
>> 
>> 	if (t->u.s.base_class)
>> @@ -1542,9 +1554,10 @@ set_gc_used_type (type_p t, enum gc_used
>> 	    int maybe_undef = 0;
>> 	    int length = 0;
>> 	    int skip = 0;
>> +	    int callback = 0;
>> 	    type_p nested_ptr = NULL;
>> 	    process_gc_options (f->opt, level, &maybe_undef, &length, &skip,
>> -				&nested_ptr);
>> +				&callback, &nested_ptr);
>> 
>> 	    if (nested_ptr && f->type->kind == TYPE_POINTER)
>> 	      set_gc_used_type (nested_ptr, GC_POINTED_TO);
>> @@ -1554,6 +1567,8 @@ set_gc_used_type (type_p t, enum gc_used
>> 	      set_gc_used_type (f->type->u.p, GC_MAYBE_POINTED_TO);
>> 	    else if (skip)
>> 	      ;			/* target type is not used through this field */
>> +	    else if (callback)
>> +	      f->type = &callback_type;
>> 	    else
>> 	      set_gc_used_type (f->type, GC_USED, allow_undefined_field_types);
>> 	  }
>> @@ -2519,6 +2534,7 @@ output_mangled_typename (outf_p of, cons
>>       {
>>       case TYPE_NONE:
>>       case TYPE_UNDEFINED:
>> +      case TYPE_CALLBACK:
>> 	gcc_unreachable ();
>> 	break;
>>       case TYPE_POINTER:
>> @@ -2719,6 +2735,8 @@ walk_type (type_p t, struct walk_type_da
>>       ;
>>     else if (strcmp (oo->name, "for_user") == 0)
>>       ;
>> +    else if (strcmp (oo->name, "callback") == 0)
>> +      ;
>>     else
>>       error_at_line (d->line, "unknown option `%s'\n", oo->name);
>> 
>> @@ -2744,6 +2762,7 @@ walk_type (type_p t, struct walk_type_da
>>     {
>>     case TYPE_SCALAR:
>>     case TYPE_STRING:
>> +    case TYPE_CALLBACK:
>>       d->process_field (t, d);
>>       break;
>> 
>> @@ -3275,6 +3294,7 @@ write_types_process_field (type_p f, con
>>       break;
>> 
>>     case TYPE_SCALAR:
>> +    case TYPE_CALLBACK:
>>       break;
>> 
>>     case TYPE_ARRAY:
>> @@ -3820,6 +3840,7 @@ write_types_local_user_process_field (ty
>>       break;
>> 
>>     case TYPE_SCALAR:
>> +    case TYPE_CALLBACK:
>>       break;
>> 
>>     case TYPE_ARRAY:
>> @@ -3906,6 +3927,13 @@ write_types_local_process_field (type_p
>>     case TYPE_SCALAR:
>>       break;
>> 
>> +    case TYPE_CALLBACK:
>> +      oprintf (d->of, "%*sif ((void *)(%s) == this_obj)\n", d->indent, "",
>> +	       d->prev_val[3]);
>> +      oprintf (d->of, "%*s  gt_pch_note_callback (&(%s), this_obj);\n",
>> +	       d->indent, "", d->val);
>> +      break;
>> +
>>     case TYPE_ARRAY:
>>     case TYPE_NONE:
>>     case TYPE_UNDEFINED:
>> @@ -4434,6 +4462,7 @@ write_root (outf_p f, pair_p v, type_p t
>>     case TYPE_UNDEFINED:
>>     case TYPE_UNION:
>>     case TYPE_LANG_STRUCT:
>> +    case TYPE_CALLBACK:
>>       error_at_line (line, "global `%s' is unimplemented type", name);
>>     }
>> }
>> @@ -4728,6 +4757,9 @@ dump_typekind (int indent, enum typekind
>>     case TYPE_ARRAY:
>>       printf ("TYPE_ARRAY");
>>       break;
>> +    case TYPE_CALLBACK:
>> +      printf ("TYPE_CALLBACK");
>> +      break;
>>     case TYPE_LANG_STRUCT:
>>       printf ("TYPE_LANG_STRUCT");
>>       break;
>> @@ -4894,6 +4926,7 @@ dump_type (int indent, type_p t)
>> 	      t->u.scalar_is_char ? "true" : "false");
>>       break;
>>     case TYPE_STRING:
>> +    case TYPE_CALLBACK:
>>       break;
>>     case TYPE_STRUCT:
>>     case TYPE_UNION:
>> --- gcc/varasm.c.jj	2021-09-28 11:34:29.343147261 +0200
>> +++ gcc/varasm.c	2021-11-08 13:26:15.032606040 +0100
>> @@ -250,8 +250,8 @@ object_block_hasher::hash (object_block
>> /* Return a new unnamed section with the given fields.  */
>> 
>> section *
>> -get_unnamed_section (unsigned int flags, void (*callback) (const void *),
>> -		     const void *data)
>> +get_unnamed_section (unsigned int flags, void (*callback) (const char *),
>> +		     const char *data)
>> {
>>   section *sect;
>> 
>> @@ -7778,9 +7778,9 @@ file_end_indicate_split_stack (void)
>>    a get_unnamed_section callback.  */
>> 
>> void
>> -output_section_asm_op (const void *directive)
>> +output_section_asm_op (const char *directive)
>> {
>> -  fprintf (asm_out_file, "%s\n", (const char *) directive);
>> +  fprintf (asm_out_file, "%s\n", directive);
>> }
>> 
>> /* Emit assembly code to switch to section NEW_SECTION.  Do nothing if
>> --- gcc/ggc-common.c.jj	2021-11-08 11:09:50.280318624 +0100
>> +++ gcc/ggc-common.c	2021-11-08 18:33:51.103390391 +0100
>> @@ -246,6 +246,7 @@ saving_hasher::equal (const ptr_data *p1
>> }
>> 
>> static hash_table<saving_hasher> *saving_htab;
>> +static vec<void *> callback_vec;
>> 
>> /* Register an object in the hash table.  */
>> 
>> @@ -278,6 +279,23 @@ gt_pch_note_object (void *obj, void *not
>>   return 1;
>> }
>> 
>> +/* Register address of a callback pointer.  */
>> +void
>> +gt_pch_note_callback (void *obj, void *base)
>> +{
>> +  void *ptr;
>> +  memcpy (&ptr, obj, sizeof (void *));
>> +  if (ptr != NULL)
>> +    {
>> +      struct ptr_data *data
>> +	= (struct ptr_data *)
>> +	  saving_htab->find_with_hash (base, POINTER_HASH (base));
>> +      gcc_assert (data);
>> +      callback_vec.safe_push ((char *) data->new_addr
>> +			      + ((char *) obj - (char *) base));
>> +    }
>> +}
>> +
>> /* Register an object in the hash table.  */
>> 
>> void
>> @@ -592,10 +610,20 @@ gt_pch_save (FILE *f)
>>   ggc_pch_finish (state.d, state.f);
>>   gt_pch_fixup_stringpool ();
>> 
>> +  unsigned num_callbacks = callback_vec.length ();
>> +  void (*pch_save) (FILE *) = &gt_pch_save;
>> +  if (fwrite (&pch_save, sizeof (pch_save), 1, f) != 1
>> +      || fwrite (&num_callbacks, sizeof (num_callbacks), 1, f) != 1
>> +      || (num_callbacks
>> +	  && fwrite (callback_vec.address (), sizeof (void *), num_callbacks,
>> +		     f) != num_callbacks))
>> +    fatal_error (input_location, "cannot write PCH file: %m");
>> +
>>   XDELETE (state.ptrs);
>>   XDELETE (this_object);
>>   delete saving_htab;
>>   saving_htab = NULL;
>> +  callback_vec.release ();
>> }
>> 
>> /* Read the state of the compiler back in from F.  */
>> @@ -649,6 +677,30 @@ gt_pch_restore (FILE *f)
>>   ggc_pch_read (f, mmi.preferred_base);
>> 
>>   gt_pch_restore_stringpool ();
>> +
>> +  void (*pch_save) (FILE *);
>> +  unsigned num_callbacks;
>> +  if (fread (&pch_save, sizeof (pch_save), 1, f) != 1
>> +      || fread (&num_callbacks, sizeof (num_callbacks), 1, f) != 1)
>> +    fatal_error (input_location, "cannot read PCH file: %m");
>> +  if (pch_save != &gt_pch_save)
>> +    {
>> +      uintptr_t bias = (uintptr_t) &gt_pch_save - (uintptr_t) pch_save;
>> +      void **ptrs = XNEWVEC (void *, num_callbacks);
>> +      unsigned i;
>> +
>> +      if (fread (ptrs, sizeof (void *), num_callbacks, f) != num_callbacks)
>> +	fatal_error (input_location, "cannot read PCH file: %m");
>> +      for (i = 0; i < num_callbacks; ++i)
>> +	{
>> +	  memcpy (&pch_save, ptrs[i], sizeof (pch_save));
>> +	  pch_save = (void (*) (FILE *)) ((uintptr_t) pch_save + bias);
>> +	  memcpy (ptrs[i], &pch_save, sizeof (pch_save));
>> +	}
>> +      XDELETE (ptrs);
>> +    }
>> +  else if (fseek (f, num_callbacks * sizeof (void *), SEEK_CUR) != 0)
>> +    fatal_error (input_location, "cannot read PCH file: %m");
>> }
>> 
>> /* Default version of HOST_HOOKS_GT_PCH_GET_ADDRESS when mmap is not present.
>> --- gcc/doc/gty.texi.jj	2021-08-19 11:42:27.363422428 +0200
>> +++ gcc/doc/gty.texi	2021-11-08 17:13:46.613882767 +0100
>> @@ -197,6 +197,15 @@ If @code{skip} is applied to a field, th
>> This is somewhat dangerous; the only safe use is in a union when one
>> field really isn't ever used.
>> 
>> +@findex callback
>> +@item callback
>> +
>> +@code{callback} should be applied to fields with pointer to function type
>> +and causes the field to be ignored similarly to @code{skip}, except when
>> +writing PCH and the field is non-NULL it will remember the field's address
>> +for relocation purposes if the process writing PCH has different load base
>> +from a process reading PCH.
>> +
>> @findex for_user
>> @item for_user
>> 
>> --- gcc/tree-core.h.jj	2021-11-04 12:27:02.377298411 +0100
>> +++ gcc/tree-core.h	2021-11-08 13:24:04.496465555 +0100
>> @@ -1964,7 +1964,7 @@ struct GTY(()) tree_function_decl {
>> struct GTY(()) tree_translation_unit_decl {
>>   struct tree_decl_common common;
>>   /* Source language of this translation unit.  Used for DWARF output.  */
>> -  const char * GTY((skip(""))) language;
>> +  const char *language;
>>   /* TODO: Non-optimization used to build this translation unit.  */
>>   /* TODO: Root of a partial DWARF tree for global types and decls.  */
>> };
>> --- gcc/gengtype-state.c.jj	2021-07-20 10:08:09.891687732 +0200
>> +++ gcc/gengtype-state.c	2021-11-08 15:19:16.157824146 +0100
>> @@ -57,6 +57,7 @@ type_lineloc (const_type_p ty)
>>     case TYPE_STRING:
>>     case TYPE_POINTER:
>>     case TYPE_ARRAY:
>> +    case TYPE_CALLBACK:
>>       return NULL;
>>     default:
>>       gcc_unreachable ();
>> @@ -171,6 +172,7 @@ private:
>>   void write_state_version (const char *version);
>>   void write_state_scalar_type (type_p current);
>>   void write_state_string_type (type_p current);
>> +  void write_state_callback_type (type_p current);
>>   void write_state_undefined_type (type_p current);
>>   void write_state_struct_union_type (type_p current, const char *kindstr);
>>   void write_state_struct_type (type_p current);
>> @@ -898,6 +900,20 @@ state_writer::write_state_string_type (t
>>     fatal ("Unexpected type in write_state_string_type");
>> }
>> 
>> +/* Write the callback type.  There is only one such thing! */
>> +void
>> +state_writer::write_state_callback_type (type_p current)
>> +{
>> +  if (current == &callback_type)
>> +    {
>> +      write_any_indent (0);
>> +      fprintf (state_file, "callback ");
>> +      write_state_common_type_content (current);
>> +    }
>> +  else
>> +    fatal ("Unexpected type in write_state_callback_type");
>> +}
>> +
>> /* Write an undefined type.  */
>> void
>> state_writer::write_state_undefined_type (type_p current)
>> @@ -1143,6 +1159,9 @@ state_writer::write_state_type (type_p c
>> 	case TYPE_STRING:
>> 	  write_state_string_type (current);
>> 	  break;
>> +	case TYPE_CALLBACK:
>> +	  write_state_callback_type (current);
>> +	  break;
>> 	}
>>     }
>> 
>> @@ -1477,6 +1496,14 @@ read_state_string_type (type_p *type)
>>   read_state_common_type_content (*type);
>> }
>> 
>> +/* Read the callback_type.  */
>> +static void
>> +read_state_callback_type (type_p *type)
>> +{
>> +  *type = &callback_type;
>> +  read_state_common_type_content (*type);
>> +}
>> +
>> 
>> /* Read a lang_bitmap representing a set of GCC front-end languages.  */
>> static void
>> @@ -1834,6 +1861,11 @@ read_state_type (type_p *current)
>> 	      next_state_tokens (1);
>> 	      read_state_string_type (current);
>> 	    }
>> +	  else if (state_token_is_name (t0, "callback"))
>> +	    {
>> +	      next_state_tokens (1);
>> +	      read_state_callback_type (current);
>> +	    }
>> 	  else if (state_token_is_name (t0, "undefined"))
>> 	    {
>> 	      *current = XCNEW (struct type);
>> --- gcc/output.h.jj	2021-09-28 11:34:29.235148754 +0200
>> +++ gcc/output.h	2021-11-08 16:26:01.172755377 +0100
>> @@ -470,7 +470,7 @@ struct GTY(()) named_section {
>> 
>> /* A callback that writes the assembly code for switching to an unnamed
>>    section.  The argument provides callback-specific data.  */
>> -typedef void (*unnamed_section_callback) (const void *);
>> +typedef void (*unnamed_section_callback) (const char *);
>> 
>> /* Information about a SECTION_UNNAMED section.  */
>> struct GTY(()) unnamed_section {
>> @@ -478,8 +478,8 @@ struct GTY(()) unnamed_section {
>> 
>>   /* The callback used to switch to the section, and the data that
>>      should be passed to the callback.  */
>> -  unnamed_section_callback GTY ((skip)) callback;
>> -  const void *GTY ((skip)) data;
>> +  unnamed_section_callback GTY ((callback)) callback;
>> +  const char *data;
>> 
>>   /* The next entry in the chain of unnamed sections.  */
>>   section *next;
>> @@ -503,7 +503,7 @@ struct GTY(()) noswitch_section {
>>   struct section_common common;
>> 
>>   /* The callback used to assemble decls in this section.  */
>> -  noswitch_section_callback GTY ((skip)) callback;
>> +  noswitch_section_callback GTY ((callback)) callback;
>> };
>> 
>> /* Information about a section, which may be named or unnamed.  */
>> @@ -538,8 +538,8 @@ extern GTY(()) section *bss_noswitch_sec
>> extern GTY(()) section *in_section;
>> extern GTY(()) bool in_cold_section_p;
>> 
>> -extern section *get_unnamed_section (unsigned int, void (*) (const void *),
>> -				     const void *);
>> +extern section *get_unnamed_section (unsigned int, void (*) (const char *),
>> +				     const char *);
>> extern section *get_section (const char *, unsigned int, tree,
>> 			     bool not_existing = false);
>> extern section *get_named_section (tree, const char *, int);
>> @@ -561,7 +561,7 @@ extern section *get_cdtor_priority_secti
>> 
>> extern bool unlikely_text_section_p (section *);
>> extern void switch_to_section (section *, tree = nullptr);
>> -extern void output_section_asm_op (const void *);
>> +extern void output_section_asm_op (const char *);
>> 
>> extern void record_tm_clone_pair (tree, tree);
>> extern void finish_tm_clone_pairs (void);
>> --- gcc/config/avr/avr.c.jj	2021-07-15 10:16:12.873583249 +0200
>> +++ gcc/config/avr/avr.c	2021-11-08 13:28:30.215676387 +0100
>> @@ -10114,10 +10114,9 @@ avr_output_bss_section_asm_op (const voi
>> /* Unnamed section callback for progmem*.data sections.  */
>> 
>> static void
>> -avr_output_progmem_section_asm_op (const void *data)
>> +avr_output_progmem_section_asm_op (const char *data)
>> {
>> -  fprintf (asm_out_file, "\t.section\t%s,\"a\",@progbits\n",
>> -           (const char*) data);
>> +  fprintf (asm_out_file, "\t.section\t%s,\"a\",@progbits\n", data);
>> }
>> 
>> 
>> --- gcc/config/darwin.c.jj	2021-10-21 10:23:27.450834602 +0200
>> +++ gcc/config/darwin.c	2021-11-08 13:27:19.106691421 +0100
>> @@ -134,7 +134,7 @@ int emit_aligned_common = false;
>>    DIRECTIVE is as for output_section_asm_op.  */
>> 
>> static void
>> -output_objc_section_asm_op (const void *directive)
>> +output_objc_section_asm_op (const char *directive)
>> {
>>   static bool been_here = false;
>> 
>> --- gcc/config/pa/pa.c.jj	2021-10-27 09:00:28.762277456 +0200
>> +++ gcc/config/pa/pa.c	2021-11-08 13:29:41.935652629 +0100
>> @@ -10011,7 +10011,7 @@ pa_arg_partial_bytes (cumulative_args_t
>>    to the default text subspace.  */
>> 
>> static void
>> -som_output_text_section_asm_op (const void *data ATTRIBUTE_UNUSED)
>> +som_output_text_section_asm_op (const char *data ATTRIBUTE_UNUSED)
>> {
>>   gcc_assert (TARGET_SOM);
>>   if (TARGET_GAS)
>> @@ -10055,7 +10055,7 @@ som_output_text_section_asm_op (const vo
>>    sections.  This function is only used with SOM.  */
>> 
>> static void
>> -som_output_comdat_data_section_asm_op (const void *data)
>> +som_output_comdat_data_section_asm_op (const char *data)
>> {
>>   in_section = NULL;
>>   output_section_asm_op (data);
>> --- gcc/config/rs6000/rs6000.c.jj	2021-11-05 00:43:22.476626062 +0100
>> +++ gcc/config/rs6000/rs6000.c	2021-11-08 13:43:22.415940789 +0100
>> @@ -20597,7 +20597,7 @@ rs6000_ms_bitfield_layout_p (const_tree
>> /* A get_unnamed_section callback, used for switching to toc_section.  */
>> 
>> static void
>> -rs6000_elf_output_toc_section_asm_op (const void *data ATTRIBUTE_UNUSED)
>> +rs6000_elf_output_toc_section_asm_op (const char *data ATTRIBUTE_UNUSED)
>> {
>>   if ((DEFAULT_ABI == ABI_AIX || DEFAULT_ABI == ABI_ELFv2)
>>       && TARGET_MINIMAL_TOC)
>> @@ -21301,35 +21301,39 @@ rs6000_xcoff_asm_globalize_label (FILE *
>>    points to the section string variable.  */
>> 
>> static void
>> -rs6000_xcoff_output_readonly_section_asm_op (const void *directive)
>> +rs6000_xcoff_output_readonly_section_asm_op (const char *directive)
>> {
>>   fprintf (asm_out_file, "\t.csect %s[RO],%s\n",
>> -	   *(const char *const *) directive,
>> +	   directive
>> +	   ? xcoff_private_rodata_section_name
>> +	   : xcoff_read_only_section_name,
>> 	   XCOFF_CSECT_DEFAULT_ALIGNMENT_STR);
>> }
>> 
>> /* Likewise for read-write sections.  */
>> 
>> static void
>> -rs6000_xcoff_output_readwrite_section_asm_op (const void *directive)
>> +rs6000_xcoff_output_readwrite_section_asm_op (const char *)
>> {
>>   fprintf (asm_out_file, "\t.csect %s[RW],%s\n",
>> -	   *(const char *const *) directive,
>> +	   xcoff_private_data_section_name,
>> 	   XCOFF_CSECT_DEFAULT_ALIGNMENT_STR);
>> }
>> 
>> static void
>> -rs6000_xcoff_output_tls_section_asm_op (const void *directive)
>> +rs6000_xcoff_output_tls_section_asm_op (const char *directive)
>> {
>>   fprintf (asm_out_file, "\t.csect %s[TL],%s\n",
>> -	   *(const char *const *) directive,
>> +	   directive
>> +	   ? xcoff_private_data_section_name
>> +	   : xcoff_tls_data_section_name,
>> 	   XCOFF_CSECT_DEFAULT_ALIGNMENT_STR);
>> }
>> 
>> /* A get_unnamed_section callback, used for switching to toc_section.  */
>> 
>> static void
>> -rs6000_xcoff_output_toc_section_asm_op (const void *data ATTRIBUTE_UNUSED)
>> +rs6000_xcoff_output_toc_section_asm_op (const char *data ATTRIBUTE_UNUSED)
>> {
>>   if (TARGET_MINIMAL_TOC)
>>     {
>> @@ -21356,26 +21360,26 @@ rs6000_xcoff_asm_init_sections (void)
>> {
>>   read_only_data_section
>>     = get_unnamed_section (0, rs6000_xcoff_output_readonly_section_asm_op,
>> -			   &xcoff_read_only_section_name);
>> +			   NULL);
>> 
>>   private_data_section
>>     = get_unnamed_section (SECTION_WRITE,
>> 			   rs6000_xcoff_output_readwrite_section_asm_op,
>> -			   &xcoff_private_data_section_name);
>> +			   NULL);
>> 
>>   read_only_private_data_section
>>     = get_unnamed_section (0, rs6000_xcoff_output_readonly_section_asm_op,
>> -			   &xcoff_private_rodata_section_name);
>> +			   "");
>> 
>>   tls_data_section
>>     = get_unnamed_section (SECTION_TLS,
>> 			   rs6000_xcoff_output_tls_section_asm_op,
>> -			   &xcoff_tls_data_section_name);
>> +			   NULL);
>> 
>>   tls_private_data_section
>>     = get_unnamed_section (SECTION_TLS,
>> 			   rs6000_xcoff_output_tls_section_asm_op,
>> -			   &xcoff_private_data_section_name);
>> +			   "");
>> 
>>   toc_section
>>     = get_unnamed_section (0, rs6000_xcoff_output_toc_section_asm_op, NULL);
>> --- gcc/c-family/c-pch.c.jj	2021-06-02 10:08:14.149450407 +0200
>> +++ gcc/c-family/c-pch.c	2021-11-08 17:34:17.302343697 +0100
>> @@ -54,7 +54,6 @@ struct c_pch_validity
>> {
>>   uint32_t pch_write_symbols;
>>   signed char match[MATCH_SIZE];
>> -  void (*pch_init) (void);
>>   size_t target_data_length;
>> };
>> 
>> @@ -117,7 +116,6 @@ pch_init (void)
>> 	gcc_assert (v.match[i] == *pch_matching[i].flag_var);
>>       }
>>   }
>> -  v.pch_init = &pch_init;
>>   target_validity = targetm.get_pch_validity (&v.target_data_length);
>> 
>>   if (fwrite (partial_pch, IDENT_LENGTH, 1, f) != 1
>> @@ -278,19 +276,6 @@ c_common_valid_pch (cpp_reader *pfile, c
>> 	}
>>   }
>> 
>> -  /* If the text segment was not loaded at the same address as it was
>> -     when the PCH file was created, function pointers loaded from the
>> -     PCH will not be valid.  We could in theory remap all the function
>> -     pointers, but no support for that exists at present.
>> -     Since we have the same executable, it should only be necessary to
>> -     check one function.  */
>> -  if (v.pch_init != &pch_init)
>> -    {
>> -      cpp_warning (pfile, CPP_W_INVALID_PCH,
>> -		   "%s: had text segment at different address", name);
>> -      return 2;
>> -    }
>> -
>>   /* Check the target-specific validity data.  */
>>   {
>>     void *this_file_data = xmalloc (v.target_data_length);
>> --- libcpp/include/line-map.h.jj	2021-11-01 14:37:06.697853154 +0100
>> +++ libcpp/include/line-map.h	2021-11-08 16:16:34.562837006 +0100
>> @@ -803,11 +803,11 @@ public:
>>   unsigned int max_column_hint;
>> 
>>   /* The allocator to use when resizing 'maps', defaults to xrealloc.  */
>> -  line_map_realloc reallocator;
>> +  line_map_realloc GTY((callback)) reallocator;
>> 
>>   /* The allocators' function used to know the actual size it
>>      allocated, for a certain allocation size requested.  */
>> -  line_map_round_alloc_size_func round_alloc_size;
>> +  line_map_round_alloc_size_func GTY((callback)) round_alloc_size;
>> 
>>   struct location_adhoc_data_map location_adhoc_data_map;
>> 
>> 
>> 
>> 	Jakub
>> 
> 
> -- 
> Richard Biener <rguenther@suse.de>
> SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
> Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)



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