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Change HASH_UNUSED_ENTRY_KEY from Qunbound to NULL float

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This removes hacks from code that had to be careful not to use
Qunbound as a hash table key, at the cost of a minor hack in
the GC marker.

* src/lisp.h (INVALID_LISP_VALUE, HASH_UNUSED_ENTRY_KEY):
Define as a null-pointer float.
* src/alloc.c (process_mark_stack): Add hack to ignore that value.
* src/pdumper.c (dump_object_needs_dumping_p)
(pdumper_init_symbol_unbound, pdumper_load):
* src/print.c (PRINT_CIRCLE_CANDIDATE_P): Remove hacks for Qunbound.
This commit is contained in:
Mattias Engdegård 2024-01-19 18:31:06 +01:00
parent 50201e03b9
commit 1d754c7960
4 changed files with 29 additions and 29 deletions
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24
src/alloc.c
View file

@ -7293,6 +7293,9 @@ process_mark_stack (ptrdiff_t base_sp)
struct Lisp_Hash_Table *h = (struct Lisp_Hash_Table *)ptr;
set_vector_marked (ptr);
if (h->weakness == Weak_None)
/* The values pushed here may include
HASH_UNUSED_ENTRY_KEY, which this function must
cope with. */
mark_stack_push_values (h->key_and_value,
2 * h->table_size);
else
@ -7437,14 +7440,19 @@ process_mark_stack (ptrdiff_t base_sp)
}
case Lisp_Float:
CHECK_ALLOCATED_AND_LIVE (live_float_p, MEM_TYPE_FLOAT);
/* Do not mark floats stored in a dump image: these floats are
"cold" and do not have mark bits. */
if (pdumper_object_p (XFLOAT (obj)))
eassert (pdumper_cold_object_p (XFLOAT (obj)));
else if (!XFLOAT_MARKED_P (XFLOAT (obj)))
XFLOAT_MARK (XFLOAT (obj));
break;
{
struct Lisp_Float *f = XFLOAT (obj);
if (!f)
break; /* for HASH_UNUSED_ENTRY_KEY */
CHECK_ALLOCATED_AND_LIVE (live_float_p, MEM_TYPE_FLOAT);
/* Do not mark floats stored in a dump image: these floats are
"cold" and do not have mark bits. */
if (pdumper_object_p (f))
eassert (pdumper_cold_object_p (f));
else if (!XFLOAT_MARKED_P (f))
XFLOAT_MARK (f);
break;
}
case_Lisp_Int:
break;

7
src/lisp.h
View file

@ -2515,8 +2515,13 @@ struct Lisp_Hash_Table
struct Lisp_Hash_Table *next_weak;
} GCALIGNED_STRUCT;
/* A specific Lisp_Object that is not a valid Lisp value.
We need to be careful not to leak this value into machinery
where it may be treated as one; we'd get a segfault if lucky. */
#define INVALID_LISP_VALUE make_lisp_ptr (NULL, Lisp_Float)
/* Key value that marks an unused hash table entry. */
#define HASH_UNUSED_ENTRY_KEY Qunbound
#define HASH_UNUSED_ENTRY_KEY INVALID_LISP_VALUE
/* KEY is a key of an unused hash table entry. */
INLINE bool

19
src/pdumper.c
View file

@ -1337,9 +1337,7 @@ dump_object_needs_dumping_p (Lisp_Object object)
included in the dump despite all references to them being
bitwise-invariant. */
return (!dump_object_self_representing_p (object)
|| (dump_object_emacs_ptr (object)
/* Don't dump Qunbound -- it's not a legal hash table key. */
&& !BASE_EQ (object, Qunbound)));
|| dump_object_emacs_ptr (object));
}
static void
@ -2553,19 +2551,6 @@ dump_symbol (struct dump_context *ctx,
return offset;
}
/* Give Qunbound its name.
All other symbols are dumped and loaded but not Qunbound because it
cannot be used as a key in a hash table.
FIXME: A better solution would be to use a value other than Qunbound
as a marker for unused entries in hash tables. */
static void
pdumper_init_symbol_unbound (void)
{
eassert (NILP (SYMBOL_NAME (Qunbound)));
const char *name = "unbound";
init_symbol (Qunbound, make_pure_c_string (name, strlen (name)));
}
static dump_off
dump_vectorlike_generic (struct dump_context *ctx,
const union vectorlike_header *header)
@ -5767,8 +5752,6 @@ pdumper_load (const char *dump_filename, char *argv0)
for (int i = 0; i < nr_dump_hooks; ++i)
dump_hooks[i] ();
pdumper_init_symbol_unbound ();
#ifdef HAVE_NATIVE_COMP
pdumper_set_emacs_execdir (argv0);
#else

8
src/print.c
View file

@ -1305,8 +1305,7 @@ print (Lisp_Object obj, Lisp_Object printcharfun, bool escapeflag)
|| RECORDP (obj))) \
|| (! NILP (Vprint_gensym) \
&& SYMBOLP (obj) \
&& !SYMBOL_INTERNED_P (obj) \
&& !hash_unused_entry_key_p (obj)))
&& !SYMBOL_INTERNED_P (obj)))
/* The print preprocess stack, used to traverse data structures. */
@ -1392,6 +1391,9 @@ static void
print_preprocess (Lisp_Object obj)
{
eassert (!NILP (Vprint_circle));
/* The ppstack may contain HASH_UNUSED_ENTRY_KEY which is an invalid
Lisp value. Make sure that our filter stops us from traversing it. */
eassert (!PRINT_CIRCLE_CANDIDATE_P (HASH_UNUSED_ENTRY_KEY));
ptrdiff_t base_sp = ppstack.sp;
for (;;)
@ -1450,6 +1452,8 @@ print_preprocess (Lisp_Object obj)
if (HASH_TABLE_P (obj))
{
struct Lisp_Hash_Table *h = XHASH_TABLE (obj);
/* The values pushed here may include
HASH_UNUSED_ENTRY_KEY; see top of this function. */
pp_stack_push_values (h->key_and_value,
2 * h->table_size);
}