Do not redundantly dump constant forwarding objects

* src/pdumper.c (dump_fwd_int, dump_fwd_bool, dump_fwd_obj): Do
not redundantly dump constant forwarding descriptors; restrict
to dumping the objects being forwarded to.
(dump_fwd_buffer_obj): Copy from the dump file into bss rather
than load buffer forwarding descriptors from the dump file
itself.
(dump_fwd_kboard_obj): Delete function.
(dump_fwd): Don't return offset of dumped objects.
(dump_blv): Adjust correspondingly.
(dump_pre_dump_symbol): Improve documentation.  Record offset of
forwarding objects in relation to `emacs_basis' rather than the
dump file.
(dump_symbol): Restore forwarding descriptors to their original
values as static variables in Emacs.  This reduces the size of
dump files by an insignificant 2kb but facilitates certain kinds
of watchpoints on platforms where ASLR cannot be disabled, e.g.,
Android.

1 files changed, 52 insertions, 66 deletions

diff --git a/src/pdumper.c b/src/pdumper.c
index de213130756..1deb8473956 100644
--- a/src/pdumper.c
+++ b/src/pdumper.c
@@ -2293,35 +2293,25 @@ dump_float (struct dump_context *ctx, const struct Lisp_Float *lfloat)
   return dump_object_finish (ctx, &out, sizeof (out));
 }
 
-static dump_off
+static void
 dump_fwd_int (struct dump_context *ctx, const struct Lisp_Intfwd *intfwd)
 {
 #if CHECK_STRUCTS && !defined HASH_Lisp_Intfwd_4D887A7387
 # error "Lisp_Intfwd changed. See CHECK_STRUCTS comment in config.h."
 #endif
   dump_emacs_reloc_immediate_intmax_t (ctx, intfwd->intvar, *intfwd->intvar);
-  struct Lisp_Intfwd out;
-  dump_object_start (ctx, &out, sizeof (out));
-  DUMP_FIELD_COPY (&out, intfwd, type);
-  dump_field_emacs_ptr (ctx, &out, intfwd, &intfwd->intvar);
-  return dump_object_finish (ctx, &out, sizeof (out));
 }
 
-static dump_off
+static void
 dump_fwd_bool (struct dump_context *ctx, const struct Lisp_Boolfwd *boolfwd)
 {
 #if CHECK_STRUCTS && !defined (HASH_Lisp_Boolfwd_0EA1C7ADCC)
 # error "Lisp_Boolfwd changed. See CHECK_STRUCTS comment in config.h."
 #endif
   dump_emacs_reloc_immediate_bool (ctx, boolfwd->boolvar, *boolfwd->boolvar);
-  struct Lisp_Boolfwd out;
-  dump_object_start (ctx, &out, sizeof (out));
-  DUMP_FIELD_COPY (&out, boolfwd, type);
-  dump_field_emacs_ptr (ctx, &out, boolfwd, &boolfwd->boolvar);
-  return dump_object_finish (ctx, &out, sizeof (out));
 }
 
-static dump_off
+static void
 dump_fwd_obj (struct dump_context *ctx, const struct Lisp_Objfwd *objfwd)
 {
 #if CHECK_STRUCTS && !defined (HASH_Lisp_Objfwd_45D3E513DC)
@@ -2331,14 +2321,9 @@ dump_fwd_obj (struct dump_context *ctx, const struct Lisp_Objfwd *objfwd)
                       ctx->staticpro_table,
                       Qnil)))
     dump_emacs_reloc_to_lv (ctx, objfwd->objvar, *objfwd->objvar);
-  struct Lisp_Objfwd out;
-  dump_object_start (ctx, &out, sizeof (out));
-  DUMP_FIELD_COPY (&out, objfwd, type);
-  dump_field_emacs_ptr (ctx, &out, objfwd, &objfwd->objvar);
-  return dump_object_finish (ctx, &out, sizeof (out));
 }
 
-static dump_off
+static void
 dump_fwd_buffer_obj (struct dump_context *ctx,
                      const struct Lisp_Buffer_Objfwd *buffer_objfwd)
 {
@@ -2346,59 +2331,49 @@ dump_fwd_buffer_obj (struct dump_context *ctx,
 # error "Lisp_Buffer_Objfwd changed. See CHECK_STRUCTS comment in config.h."
 #endif
   struct Lisp_Buffer_Objfwd out;
+  dump_off off;
+
   dump_object_start (ctx, &out, sizeof (out));
   DUMP_FIELD_COPY (&out, buffer_objfwd, type);
   DUMP_FIELD_COPY (&out, buffer_objfwd, offset);
   dump_field_lv (ctx, &out, buffer_objfwd, &buffer_objfwd->predicate,
                  WEIGHT_NORMAL);
-  return dump_object_finish (ctx, &out, sizeof (out));
-}
+  off = dump_object_finish (ctx, &out, sizeof out);
 
-static dump_off
-dump_fwd_kboard_obj (struct dump_context *ctx,
-                     const struct Lisp_Kboard_Objfwd *kboard_objfwd)
-{
-#if CHECK_STRUCTS && !defined (HASH_Lisp_Kboard_Objfwd_CAA7E71069)
-# error "Lisp_Intfwd changed. See CHECK_STRUCTS comment in config.h."
-#endif
-  struct Lisp_Kboard_Objfwd out;
-  dump_object_start (ctx, &out, sizeof (out));
-  DUMP_FIELD_COPY (&out, kboard_objfwd, type);
-  DUMP_FIELD_COPY (&out, kboard_objfwd, offset);
-  return dump_object_finish (ctx, &out, sizeof (out));
+  /* Copy this fwd from the dump to the buffer fwd in Emacs.  */
+  dump_emacs_reloc_copy_from_dump (ctx, off, (void *) buffer_objfwd,
+                                   sizeof out);
 }
 
-static dump_off
+static void
 dump_fwd (struct dump_context *ctx, lispfwd fwd)
 {
 #if CHECK_STRUCTS && !defined (HASH_Lisp_Fwd_Type_9CBA6EE55E)
 # error "Lisp_Fwd_Type changed. See CHECK_STRUCTS comment in config.h."
 #endif
   void const *p = fwd.fwdptr;
-  dump_off offset;
 
   switch (XFWDTYPE (fwd))
     {
     case Lisp_Fwd_Int:
-      offset = dump_fwd_int (ctx, p);
+      dump_fwd_int (ctx, p);
       break;
     case Lisp_Fwd_Bool:
-      offset = dump_fwd_bool (ctx, p);
+      dump_fwd_bool (ctx, p);
       break;
     case Lisp_Fwd_Obj:
-      offset = dump_fwd_obj (ctx, p);
+      dump_fwd_obj (ctx, p);
       break;
     case Lisp_Fwd_Buffer_Obj:
-      offset = dump_fwd_buffer_obj (ctx, p);
+      dump_fwd_buffer_obj (ctx, p);
       break;
+      /* The default kboard's contents are not meant to appear in the
+         dump file.  */
     case Lisp_Fwd_Kboard_Obj:
-      offset = dump_fwd_kboard_obj (ctx, p);
       break;
     default:
       emacs_abort ();
     }
-
-  return offset;
 }
 
 static dump_off
@@ -2413,16 +2388,16 @@ dump_blv (struct dump_context *ctx,
   DUMP_FIELD_COPY (&out, blv, local_if_set);
   DUMP_FIELD_COPY (&out, blv, found);
   if (blv->fwd.fwdptr)
-    dump_field_fixup_later (ctx, &out, blv, &blv->fwd.fwdptr);
+    {
+      eassert (XFWDTYPE (blv->fwd) != Lisp_Fwd_Buffer_Obj);
+      dump_field_emacs_ptr (ctx, &out, blv, &blv->fwd.fwdptr);
+    }
   dump_field_lv (ctx, &out, blv, &blv->where, WEIGHT_NORMAL);
   dump_field_lv (ctx, &out, blv, &blv->defcell, WEIGHT_STRONG);
   dump_field_lv (ctx, &out, blv, &blv->valcell, WEIGHT_STRONG);
   dump_off offset = dump_object_finish (ctx, &out, sizeof (out));
   if (blv->fwd.fwdptr)
-    dump_remember_fixup_ptr_raw
-      (ctx,
-       offset + dump_offsetof (struct Lisp_Buffer_Local_Value, fwd),
-       dump_fwd (ctx, blv->fwd));
+    dump_fwd (ctx, blv->fwd);
   return offset;
 }
 
@@ -2443,6 +2418,14 @@ dump_remember_symbol_aux (struct dump_context *ctx,
   Fputhash (symbol, dump_off_to_lisp (offset), ctx->symbol_aux);
 }
 
+/* Dump auxiliary information attached to SYMBOL, a symbol that will be
+   copied into Emacs's core from the dump file.  If SYMBOL is localized,
+   generate a copy of its buffer local storage and arrange that the
+   symbol redirect to the same.  Otherwise, if SYMBOL is forwarded,
+   arrange to restore the contents of the forwarding structure and/or
+   dump its references as the case may be; the former is only necessary
+   in the case of buffer objfwds, which are initialized at runtime.  */
+
 static void
 dump_pre_dump_symbol (struct dump_context *ctx, struct Lisp_Symbol *symbol)
 {
@@ -2457,8 +2440,9 @@ dump_pre_dump_symbol (struct dump_context *ctx, struct Lisp_Symbol *symbol)
                                 dump_blv (ctx, symbol->u.s.val.blv));
       break;
     case SYMBOL_FORWARDED:
+      dump_fwd (ctx, symbol->u.s.val.fwd);
       dump_remember_symbol_aux (ctx, symbol_lv,
-                                dump_fwd (ctx, symbol->u.s.val.fwd));
+                                emacs_offset (symbol->u.s.val.fwd.fwdptr));
       break;
     default:
       break;
@@ -2467,9 +2451,8 @@ dump_pre_dump_symbol (struct dump_context *ctx, struct Lisp_Symbol *symbol)
 }
 
 static dump_off
-dump_symbol (struct dump_context *ctx,
-             Lisp_Object object,
-             dump_off offset)
+dump_symbol (struct dump_context *ctx, Lisp_Object object,
+             dump_off offset)
 {
 #if CHECK_STRUCTS && !defined HASH_Lisp_Symbol_E0ADAF2F24
 # error "Lisp_Symbol changed. See CHECK_STRUCTS comment in config.h."
@@ -2477,6 +2460,7 @@ dump_symbol (struct dump_context *ctx,
 #if CHECK_STRUCTS && !defined (HASH_symbol_redirect_EA72E4BFF5)
 # error "symbol_redirect changed. See CHECK_STRUCTS comment in config.h."
 #endif
+  dump_off aux_offset;
 
   if (ctx->flags.defer_symbols)
     {
@@ -2524,8 +2508,13 @@ dump_symbol (struct dump_context *ctx,
       dump_field_fixup_later (ctx, &out, symbol, &symbol->u.s.val.blv);
       break;
     case SYMBOL_FORWARDED:
-      dump_field_fixup_later (ctx, &out, symbol, &symbol->u.s.val.fwd);
+      /* This forwarding descriptor is in Emacs's core, but the symbol
+         is initialized at runtime.  The next switch statement might
+         dump this value if it hasn't already been dumped by
+         dump_pre_dump_symbol.  */
+      dump_field_emacs_ptr (ctx, &out, symbol, &symbol->u.s.val.fwd.fwdptr);
       break;
+
     default:
       emacs_abort ();
     }
@@ -2535,27 +2524,24 @@ dump_symbol (struct dump_context *ctx,
                         WEIGHT_STRONG);
 
   offset = dump_object_finish (ctx, &out, sizeof (out));
-  dump_off aux_offset;
-
   switch (symbol->u.s.redirect)
     {
     case SYMBOL_LOCALIZED:
       aux_offset = dump_recall_symbol_aux (ctx, make_lisp_symbol (symbol));
-      dump_remember_fixup_ptr_raw
-        (ctx,
-         offset + dump_offsetof (struct Lisp_Symbol, u.s.val.blv),
-         (aux_offset
-          ? aux_offset
-          : dump_blv (ctx, symbol->u.s.val.blv)));
+      dump_remember_fixup_ptr_raw (ctx, offset + dump_offsetof (struct Lisp_Symbol,
+                                                                u.s.val.blv),
+                                   (aux_offset
+                                    ? aux_offset
+                                    : dump_blv (ctx, symbol->u.s.val.blv)));
       break;
     case SYMBOL_FORWARDED:
       aux_offset = dump_recall_symbol_aux (ctx, make_lisp_symbol (symbol));
-      dump_remember_fixup_ptr_raw
-        (ctx,
-         offset + dump_offsetof (struct Lisp_Symbol, u.s.val.fwd),
-         (aux_offset
-          ? aux_offset
-          : dump_fwd (ctx, symbol->u.s.val.fwd)));
+      /* Symbols interned by a defvar are not copied objects.  */
+      if (!aux_offset)
+        dump_fwd (ctx, symbol->u.s.val.fwd);
+      if (aux_offset && (aux_offset
+                         != emacs_offset (symbol->u.s.val.fwd.fwdptr)))
+        emacs_abort ();
       break;
     default:
       break;