Add C macro for hash table iteration

This removes some boilerplate code and further reduces dependencies on
hash table implementation internals.

* src/lisp.h (DOHASH): New.
* src/comp.c (compile_function, Fcomp__compile_ctxt_to_file):
* src/composite.c (composition_gstring_cache_clear_font):
* src/emacs-module.c (module_global_reference_p):
* src/fns.c (Fmaphash):
* src/json.c (lisp_to_json_nonscalar_1):
* src/minibuf.c (Ftest_completion):
* src/print.c (print):
Use it instead of a hand-written loop.

8 files changed, 59 insertions, 82 deletions

diff --git a/src/comp.c b/src/comp.c
index 3f9e738d9a7..25c4cb2f22c 100644
--- a/src/comp.c
+++ b/src/comp.c
@@ -4330,11 +4330,10 @@ compile_function (Lisp_Object func)
   declare_block (Qentry);
   Lisp_Object blocks = CALL1I (comp-func-blocks, func);
   struct Lisp_Hash_Table *ht = XHASH_TABLE (blocks);
-  for (ptrdiff_t i = 0; i < HASH_TABLE_SIZE (ht); i++)
+  DOHASH (ht, i)
     {
       Lisp_Object block_name = HASH_KEY (ht, i);
-      if (!EQ (block_name, Qentry)
-          && !hash_unused_entry_key_p (block_name))
+      if (!EQ (block_name, Qentry))
         declare_block (block_name);
     }
 
@@ -4344,24 +4343,21 @@ compile_function (Lisp_Object func)
                                 gcc_jit_lvalue_as_rvalue (comp.func_relocs));
 
 
-  for (ptrdiff_t i = 0; i < HASH_TABLE_SIZE (ht); i++)
+  DOHASH (ht, i)
     {
       Lisp_Object block_name = HASH_KEY (ht, i);
-      if (!hash_unused_entry_key_p (block_name))
+      Lisp_Object block = HASH_VALUE (ht, i);
+      Lisp_Object insns = CALL1I (comp-block-insns, block);
+      if (NILP (block) || NILP (insns))
+        xsignal1 (Qnative_ice,
+                  build_string ("basic block is missing or empty"));
+
+      comp.block = retrive_block (block_name);
+      while (CONSP (insns))
         {
-          Lisp_Object block = HASH_VALUE (ht, i);
-          Lisp_Object insns = CALL1I (comp-block-insns, block);
-          if (NILP (block) || NILP (insns))
-            xsignal1 (Qnative_ice,
-                      build_string ("basic block is missing or empty"));
-
-          comp.block = retrive_block (block_name);
-          while (CONSP (insns))
-            {
-              Lisp_Object insn = XCAR (insns);
-              emit_limple_insn (insn);
-              insns = XCDR (insns);
-            }
+          Lisp_Object insn = XCAR (insns);
+          emit_limple_insn (insn);
+          insns = XCDR (insns);
         }
     }
   const char *err =  gcc_jit_context_get_first_error (comp.ctxt);
@@ -4965,14 +4961,10 @@ DEFUN ("comp--compile-ctxt-to-file", Fcomp__compile_ctxt_to_file,
 
   struct Lisp_Hash_Table *func_h =
     XHASH_TABLE (CALL1I (comp-ctxt-funcs-h, Vcomp_ctxt));
-  for (ptrdiff_t i = 0; i < HASH_TABLE_SIZE (func_h); i++)
-    if (!hash_unused_entry_key_p (HASH_KEY (func_h, i)))
-      declare_function (HASH_VALUE (func_h, i));
+  DOHASH (func_h, i) declare_function (HASH_VALUE (func_h, i));
   /* Compile all functions. Can't be done before because the
      relocation structs has to be already defined.  */
-  for (ptrdiff_t i = 0; i < HASH_TABLE_SIZE (func_h); i++)
-    if (!hash_unused_entry_key_p (HASH_KEY (func_h, i)))
-      compile_function (HASH_VALUE (func_h, i));
+  DOHASH (func_h, i) compile_function (HASH_VALUE (func_h, i));
 
   /* Work around bug#46495 (GCC PR99126). */
 #if defined (WIDE_EMACS_INT)                                            \
diff --git a/src/composite.c b/src/composite.c
index 78c884dd72d..d9233fe0cc0 100644
--- a/src/composite.c
+++ b/src/composite.c
@@ -687,17 +687,13 @@ composition_gstring_cache_clear_font (Lisp_Object font_object)
 {
   struct Lisp_Hash_Table *h = XHASH_TABLE (gstring_hash_table);
 
-  for (ptrdiff_t i = 0; i < HASH_TABLE_SIZE (h); ++i)
+  DOHASH (h, i)
     {
       Lisp_Object k = HASH_KEY (h, i);
+      Lisp_Object gstring = HASH_VALUE (h, i);
 
-      if (!hash_unused_entry_key_p (k))
-        {
-          Lisp_Object gstring = HASH_VALUE (h, i);
-
-          if (EQ (LGSTRING_FONT (gstring), font_object))
-            hash_remove_from_table (h, k);
-        }
+      if (EQ (LGSTRING_FONT (gstring), font_object))
+        hash_remove_from_table (h, k);
     }
 }
 
diff --git a/src/emacs-module.c b/src/emacs-module.c
index 00ae33dfa2c..77dd2b9152c 100644
--- a/src/emacs-module.c
+++ b/src/emacs-module.c
@@ -410,12 +410,9 @@ module_global_reference_p (emacs_value v, ptrdiff_t *n)
   struct Lisp_Hash_Table *h = XHASH_TABLE (Vmodule_refs_hash);
   /* Note that we can't use `hash_lookup' because V might be a local
      reference that's identical to some global reference.  */
-  for (ptrdiff_t i = 0; i < HASH_TABLE_SIZE (h); ++i)
-    {
-      if (!hash_unused_entry_key_p (HASH_KEY (h, i))
-          && &XMODULE_GLOBAL_REFERENCE (HASH_VALUE (h, i))->value == v)
-        return true;
-    }
+  DOHASH (h, i)
+    if (&XMODULE_GLOBAL_REFERENCE (HASH_VALUE (h, i))->value == v)
+      return true;
   /* Only used for debugging, so we don't care about overflow, just
      make sure the operation is defined.  */
   ckd_add (n, *n, h->count);
diff --git a/src/fns.c b/src/fns.c
index 15bbd270311..4531b237824 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -5655,14 +5655,7 @@ FUNCTION is called with two arguments, KEY and VALUE.
   (Lisp_Object function, Lisp_Object table)
 {
   struct Lisp_Hash_Table *h = check_hash_table (table);
-
-  for (ptrdiff_t i = 0; i < HASH_TABLE_SIZE (h); ++i)
-    {
-      Lisp_Object k = HASH_KEY (h, i);
-      if (!hash_unused_entry_key_p (k))
-        call2 (function, k, HASH_VALUE (h, i));
-    }
-
+  DOHASH (h, i) call2 (function, HASH_KEY (h, i), HASH_VALUE (h, i));
   return Qnil;
 }
 
diff --git a/src/json.c b/src/json.c
index 266905f1c34..5434780ba13 100644
--- a/src/json.c
+++ b/src/json.c
@@ -361,33 +361,30 @@ lisp_to_json_nonscalar_1 (Lisp_Object lisp,
       json = json_check (json_object ());
       count = SPECPDL_INDEX ();
       record_unwind_protect_ptr (json_release_object, json);
-      for (ptrdiff_t i = 0; i < HASH_TABLE_SIZE (h); ++i)
+      DOHASH (h, i)
         {
           Lisp_Object key = HASH_KEY (h, i);
-          if (!hash_unused_entry_key_p (key))
-            {
-              CHECK_STRING (key);
-              Lisp_Object ekey = json_encode (key);
-              /* We can't specify the length, so the string must be
-                 null-terminated.  */
-              check_string_without_embedded_nulls (ekey);
-              const char *key_str = SSDATA (ekey);
-              /* Reject duplicate keys.  These are possible if the hash
-                 table test is not `equal'.  */
-              if (json_object_get (json, key_str) != NULL)
-                wrong_type_argument (Qjson_value_p, lisp);
-              int status
-                = json_object_set_new (json, key_str,
-                                       lisp_to_json (HASH_VALUE (h, i), conf));
-              if (status == -1)
-                {
-                  /* A failure can be caused either by an invalid key or
-                   by low memory.  */
-                  json_check_utf8 (ekey);
-                  json_out_of_memory ();
-                }
-            }
-        }
+          CHECK_STRING (key);
+          Lisp_Object ekey = json_encode (key);
+          /* We can't specify the length, so the string must be
+             null-terminated.  */
+          check_string_without_embedded_nulls (ekey);
+          const char *key_str = SSDATA (ekey);
+          /* Reject duplicate keys.  These are possible if the hash
+             table test is not `equal'.  */
+          if (json_object_get (json, key_str) != NULL)
+            wrong_type_argument (Qjson_value_p, lisp);
+          int status
+            = json_object_set_new (json, key_str,
+                                   lisp_to_json (HASH_VALUE (h, i), conf));
+          if (status == -1)
+            {
+              /* A failure can be caused either by an invalid key or
+                 by low memory.  */
+              json_check_utf8 (ekey);
+              json_out_of_memory ();
+            }
+        }
     }
   else if (NILP (lisp))
     return json_check (json_object ());
diff --git a/src/lisp.h b/src/lisp.h
index f0beafba42c..edea7cc23bb 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -2579,6 +2579,14 @@ hash_from_key (struct Lisp_Hash_Table *h, Lisp_Object key)
   return h->test->hashfn (key, h);
 }
 
+/* Hash table iteration construct (roughly an inlined maphash):
+   Iterate IDXVAR as index over valid entries of TABLE.
+   The body may remove the current entry or alter its value slot, but not
+   mutate TABLE in any other way.  */
+#define DOHASH(TABLE, IDXVAR)                                           \
+  for (ptrdiff_t IDXVAR = 0; IDXVAR < (TABLE)->table_size; IDXVAR++)    \
+    if (!hash_unused_entry_key_p (HASH_KEY (TABLE, IDXVAR)))
+
 void hash_table_thaw (Lisp_Object hash_table);
 
 /* Default size for hash tables if not specified.  */
diff --git a/src/minibuf.c b/src/minibuf.c
index 8198dc0f360..857b62d94f0 100644
--- a/src/minibuf.c
+++ b/src/minibuf.c
@@ -2114,10 +2114,10 @@ the values STRING, PREDICATE and `lambda'.  */)
           goto found_matching_key;
         }
       else
-        for (i = 0; i < HASH_TABLE_SIZE (h); ++i)
+        DOHASH (h, j)
           {
+            i = j;
             tem = HASH_KEY (h, i);
-            if (hash_unused_entry_key_p (tem)) continue;
             Lisp_Object strkey = (SYMBOLP (tem) ? Fsymbol_name (tem) : tem);
             if (!STRINGP (strkey)) continue;
             if (BASE_EQ (Fcompare_strings (string, Qnil, Qnil,
diff --git a/src/print.c b/src/print.c
index 61999c096aa..c61fb3cd574 100644
--- a/src/print.c
+++ b/src/print.c
@@ -1285,15 +1285,9 @@ print (Lisp_Object obj, Lisp_Object printcharfun, bool escapeflag)
         { /* Remove unnecessary objects, which appear only once in OBJ;
              that is, whose status is Qt.  */
           struct Lisp_Hash_Table *h = XHASH_TABLE (Vprint_number_table);
-          ptrdiff_t i;
-
-          for (i = 0; i < HASH_TABLE_SIZE (h); ++i)
-            {
-              Lisp_Object key =  HASH_KEY (h, i);
-              if (!hash_unused_entry_key_p (key)
-                  && EQ (HASH_VALUE (h, i), Qt))
-                Fremhash (key, Vprint_number_table);
-            }
+          DOHASH (h, i)
+            if (EQ (HASH_VALUE (h, i), Qt))
+              Fremhash (HASH_KEY (h, i), Vprint_number_table);
         }
     }