gcc/SOURCES/gcc8-pch-tweaks.patch

commit fe7c3ecff1f9c0520090a77fa824d8c5d9dbec12
Author: Jakub Jelinek <jakub@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  <jakub@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.

commit 4dc6d19222581c77a174d44d97507d234fb7e39b
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Mon Dec 6 11:18:58 2021 +0100

    avr: Fix AVR build [PR71934]
    
    On Mon, Dec 06, 2021 at 11:00:30AM +0100, Martin Liška wrote:
    > Jakub, I think the patch broke avr-linux target:
    >
    > g++  -fno-PIE -c   -g   -DIN_GCC  -DCROSS_DIRECTORY_STRUCTURE   -fno-exceptions -fno-rtti -fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings -Wcast-qual -Wno-erro
    > /home/marxin/Programming/gcc/gcc/config/avr/avr.c: In function ‘void avr_output_data_section_asm_op(const void*)’:
    > /home/marxin/Programming/gcc/gcc/config/avr/avr.c:10097:26: error: invalid conversion from ‘const void*’ to ‘const char*’ [-fpermissive]
    
    This patch fixes that.
    
    2021-12-06  Jakub Jelinek  <jakub@redhat.com>
    
            PR pch/71934
            * config/avr/avr.c (avr_output_data_section_asm_op,
            avr_output_bss_section_asm_op): Change argument type from const void *
            to const char *.

diff --git a/gcc/c-family/c-pch.c b/gcc/c-family/c-pch.c
index 5da60423354..2cafa1387bb 100644
--- a/gcc/c-family/c-pch.c
+++ b/gcc/c-family/c-pch.c
@@ -58,7 +58,6 @@ struct c_pch_validity
 {
   unsigned char debug_info_type;
   signed char match[MATCH_SIZE];
-  void (*pch_init) (void);
   size_t target_data_length;
 };
 
@@ -123,7 +122,6 @@ 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
@@ -287,20 +285,6 @@ 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)
-    {
-      if (cpp_get_options (pfile)->warn_invalid_pch)
-	cpp_error (pfile, CPP_DL_WARNING,
-		   "%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);
diff --git a/gcc/config/avr/avr.c b/gcc/config/avr/avr.c
index 200701a583c..6ba038881d6 100644
--- a/gcc/config/avr/avr.c
+++ b/gcc/config/avr/avr.c
@@ -10114,10 +10114,9 @@ avr_output_bss_section_asm_op (const void *data)
 /* 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);
 }
 
 
diff --git a/gcc/config/darwin.c b/gcc/config/darwin.c
index c5ba7927ce1..8ad5b26c980 100644
--- a/gcc/config/darwin.c
+++ b/gcc/config/darwin.c
@@ -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;
 
diff --git a/gcc/config/pa/pa.c b/gcc/config/pa/pa.c
index f22d25a4066..2b10ef34061 100644
--- a/gcc/config/pa/pa.c
+++ b/gcc/config/pa/pa.c
@@ -10009,7 +10009,7 @@ pa_arg_partial_bytes (cumulative_args_t cum_v, const function_arg_info &arg)
    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)
@@ -10053,7 +10053,7 @@ som_output_text_section_asm_op (const void *data ATTRIBUTE_UNUSED)
    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);
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 945157b1c1a..34089743759 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -20599,7 +20599,7 @@ rs6000_ms_bitfield_layout_p (const_tree record_type)
 /* 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)
@@ -21303,35 +21303,39 @@ rs6000_xcoff_asm_globalize_label (FILE *stream, const char *name)
    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)
     {
@@ -21358,26 +21362,26 @@ 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);
diff --git a/gcc/doc/gty.texi b/gcc/doc/gty.texi
index b996ff2c44e..ca2c8404894 100644
--- a/gcc/doc/gty.texi
+++ b/gcc/doc/gty.texi
@@ -205,6 +205,15 @@ If @code{skip} is applied to a field, the type machinery will ignore it.
 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
 
diff --git a/gcc/gengtype-state.c b/gcc/gengtype-state.c
index ac9d536963f..36a96e84574 100644
--- a/gcc/gengtype-state.c
+++ b/gcc/gengtype-state.c
@@ -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 (type_p current)
     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 current)
 	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);
diff --git a/gcc/gengtype.c b/gcc/gengtype.c
index a77cfd92bfa..b9daaa43689 100644
--- a/gcc/gengtype.c
+++ b/gcc/gengtype.c
@@ -172,6 +172,7 @@ dbgprint_count_type_at (const char *fil, int lin, const char *msg, type_p t)
   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, int lin, const char *msg, type_p t)
 	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, int lin, const char *msg, type_p t)
     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 gc_used_enum level, int *maybe_undef,
       *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_enum level,
 	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_enum level,
 	    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_enum level,
 	      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, const_type_p t)
       {
       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_data *d)
       ;
     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_data *d)
     {
     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, const struct walk_type_data *d)
       break;
 
     case TYPE_SCALAR:
+    case TYPE_CALLBACK:
       break;
 
     case TYPE_ARRAY:
@@ -3820,6 +3840,7 @@ write_types_local_user_process_field (type_p f, const struct walk_type_data *d)
       break;
 
     case TYPE_SCALAR:
+    case TYPE_CALLBACK:
       break;
 
     case TYPE_ARRAY:
@@ -3906,6 +3927,13 @@ write_types_local_process_field (type_p f, const struct walk_type_data *d)
     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 type, const char *name, int has_length,
     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 kind)
     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:
diff --git a/gcc/gengtype.h b/gcc/gengtype.h
index 8a7a54957ea..8fa7064ca85 100644
--- a/gcc/gengtype.h
+++ b/gcc/gengtype.h
@@ -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)					\
diff --git a/gcc/ggc-common.c b/gcc/ggc-common.c
index b6abed1d9a2..7c998e95473 100644
--- a/gcc/ggc-common.c
+++ b/gcc/ggc-common.c
@@ -256,6 +256,7 @@ 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.  */
 
@@ -288,6 +289,23 @@ 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
@@ -582,10 +600,20 @@ 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.  */
@@ -639,6 +667,30 @@ 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.
diff --git a/gcc/ggc.h b/gcc/ggc.h
index 5e921d957fd..c005f7e0412 100644
--- a/gcc/ggc.h
+++ b/gcc/ggc.h
@@ -46,6 +46,10 @@ typedef void (*gt_handle_reorder) (void *, void *, gt_pointer_operator,
 /* 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);
diff --git a/gcc/output.h b/gcc/output.h
index 8f6f15308f4..4a23795bf7e 100644
--- a/gcc/output.h
+++ b/gcc/output.h
@@ -456,7 +456,7 @@ 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 {
@@ -464,8 +464,8 @@ 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;
@@ -489,7 +489,7 @@ 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.  */
@@ -524,8 +524,8 @@ 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);
 extern section *get_named_section (tree, const char *, int);
 extern section *get_variable_section (tree, bool);
@@ -546,7 +546,7 @@ extern section *get_cdtor_priority_secti
 
 extern bool unlikely_text_section_p (section *);
 extern void switch_to_section (section *);
-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);
diff --git a/gcc/tree-core.h b/gcc/tree-core.h
index 8ab119dc9a2..91ae5237d7e 100644
--- a/gcc/tree-core.h
+++ b/gcc/tree-core.h
@@ -1961,7 +1961,7 @@ 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.  */
 };
diff --git a/gcc/varasm.c b/gcc/varasm.c
index 9315e2c6936..aff93ca5de9 100644
--- a/gcc/varasm.c
+++ b/gcc/varasm.c
@@ -250,8 +250,8 @@ object_block_hasher::hash (object_block *old)
 /* 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
diff --git a/libcpp/include/line-map.h b/libcpp/include/line-map.h
index 8b5e2f82982..bc40e333579 100644
--- a/libcpp/include/line-map.h
+++ b/libcpp/include/line-map.h
@@ -758,11 +758,11 @@ struct GTY(()) line_maps {
 
   /* If non-null, the allocator to use when resizing 'maps'.  If null,
      xrealloc is used.  */
-  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;
 
diff --git a/gcc/config/avr/avr.c b/gcc/config/avr/avr.c
index 6ba038881d6..1c2f7d564e7 100644
--- a/gcc/config/avr/avr.c
+++ b/gcc/config/avr/avr.c
@@ -10089,7 +10089,7 @@ avr_asm_asm_output_aligned_bss (FILE *file, tree decl, const char *name,
    to track need of __do_copy_data.  */
 
 static void
-avr_output_data_section_asm_op (const void *data)
+avr_output_data_section_asm_op (const char *data)
 {
   avr_need_copy_data_p = true;
 
@@ -10102,7 +10102,7 @@ avr_output_data_section_asm_op (const void *data)
    to track need of __do_clear_bss.  */
 
 static void
-avr_output_bss_section_asm_op (const void *data)
+avr_output_bss_section_asm_op (const char *data)
 {
   avr_need_clear_bss_p = true;