From: Mattias Engdegård Date: Fri, 19 Jan 2024 17:31:06 +0000 (+0100) Subject: Change HASH_UNUSED_ENTRY_KEY from Qunbound to NULL float X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=16c49581e72588ccc0b75ace0c0d20d5ba10193d;p=emacs.git Change HASH_UNUSED_ENTRY_KEY from Qunbound to NULL float 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. (cherry picked from commit 1d754c79603f1b6e4574c7e64c1bf5fb8c6c190d) --- diff --git a/src/alloc.c b/src/alloc.c index b78445f65df..2a1690d2cff 100644 --- a/src/alloc.c +++ b/src/alloc.c @@ -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; diff --git a/src/lisp.h b/src/lisp.h index edea7cc23bb..ae78947805e 100644 --- a/src/lisp.h +++ b/src/lisp.h @@ -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 diff --git a/src/pdumper.c b/src/pdumper.c index 4602931b63a..8d030585c83 100644 --- a/src/pdumper.c +++ b/src/pdumper.c @@ -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 diff --git a/src/print.c b/src/print.c index c61fb3cd574..c99d8d5fe3a 100644 --- a/src/print.c +++ b/src/print.c @@ -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); }