Merge branch 'master' of git.sv.gnu.org:/srv/git/emacs into feature/pgtk

1 files changed, 36 insertions, 8 deletions

diff --git a/src/alloc.c b/src/alloc.c
index e57bec111e3..a17488ee1d0 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -4740,7 +4740,7 @@ live_small_vector_p (struct mem_node *m, void *p)
    marked.  */
 
 static void
-mark_maybe_pointer (void *p)
+mark_maybe_pointer (void *p, bool symbol_only)
 {
   struct mem_node *m;
 
@@ -4755,14 +4755,32 @@ mark_maybe_pointer (void *p)
      definitely _don't_ have an object.  */
   if (pdumper_object_p (p))
     {
+      /* FIXME: This code assumes that every reachable pdumper object
+         is addressed either by a pointer to the object start, or by
+         the same pointer with an LSB-style tag.  This assumption
+         fails if a pdumper object is reachable only via machine
+         addresses of non-initial object components.  Although such
+         addressing is rare in machine code generated by C compilers
+         from Emacs source code, it can occur in some cases.  To fix
+         this problem, the pdumper code should grok non-initial
+         addresses, as the non-pdumper code does.  */
+      uintptr_t mask = VALMASK & UINTPTR_MAX;
+      uintptr_t masked_p = (uintptr_t) p & mask;
+      void *po = (void *) masked_p;
+      char *cp = p;
+      char *cpo = po;
       /* Don't use pdumper_object_p_precise here! It doesn't check the
          tag bits. OBJ here might be complete garbage, so we need to
          verify both the pointer and the tag.  */
-      int type = pdumper_find_object_type (p);
-      if (pdumper_valid_object_type_p (type))
-        mark_object (type == Lisp_Symbol
-                     ? make_lisp_symbol (p)
-                     : make_lisp_ptr (p, type));
+      int type = pdumper_find_object_type (po);
+      if (pdumper_valid_object_type_p (type)
+          && (!USE_LSB_TAG || p == po || cp - cpo == type))
+        {
+          if (type == Lisp_Symbol)
+            mark_object (make_lisp_symbol (po));
+          else if (!symbol_only)
+            mark_object (make_lisp_ptr (po, type));
+        }
       return;
     }
 
@@ -4780,6 +4798,8 @@ mark_maybe_pointer (void *p)
 
         case MEM_TYPE_CONS:
           {
+            if (symbol_only)
+              return;
             struct Lisp_Cons *h = live_cons_holding (m, p);
             if (!h)
               return;
@@ -4789,6 +4809,8 @@ mark_maybe_pointer (void *p)
 
         case MEM_TYPE_STRING:
           {
+            if (symbol_only)
+              return;
             struct Lisp_String *h = live_string_holding (m, p);
             if (!h)
               return;
@@ -4807,6 +4829,8 @@ mark_maybe_pointer (void *p)
 
         case MEM_TYPE_FLOAT:
           {
+            if (symbol_only)
+              return;
             struct Lisp_Float *h = live_float_holding (m, p);
             if (!h)
               return;
@@ -4816,6 +4840,8 @@ mark_maybe_pointer (void *p)
 
         case MEM_TYPE_VECTORLIKE:
           {
+            if (symbol_only)
+              return;
             struct Lisp_Vector *h = live_large_vector_holding (m, p);
             if (!h)
               return;
@@ -4825,6 +4851,8 @@ mark_maybe_pointer (void *p)
 
         case MEM_TYPE_VECTOR_BLOCK:
           {
+            if (symbol_only)
+              return;
             struct Lisp_Vector *h = live_small_vector_holding (m, p);
             if (!h)
               return;
@@ -4886,7 +4914,7 @@ mark_memory (void const *start, void const *end)
   for (pp = start; (void const *) pp < end; pp += GC_POINTER_ALIGNMENT)
     {
       void *p = *(void *const *) pp;
-      mark_maybe_pointer (p);
+      mark_maybe_pointer (p, false);
 
       /* Unmask any struct Lisp_Symbol pointer that make_lisp_symbol
          previously disguised by adding the address of 'lispsym'.
@@ -4895,7 +4923,7 @@ mark_memory (void const *start, void const *end)
          non-adjacent words and P might be the low-order word's value.  */
       intptr_t ip;
       INT_ADD_WRAPV ((intptr_t) p, (intptr_t) lispsym, &ip);
-      mark_maybe_pointer ((void *) ip);
+      mark_maybe_pointer ((void *) ip, true);
     }
 }