Bug #10623: rb_hash_delete() can return Qundef in 2.2-rc1

• Status: Closed
• Assignee: -
• Target version: 2.2.0
• ruby -v: ruby 2.2.0dev [x86_64-darwin14]
• Backport: 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: DONE

[tmm1 (Aman Karmani)]

The behavior of rb_hash_delete() has changed from 2.1. Before, it would always return Qnil or VALUE. Now it can also return Qundef, which is breaking the posix-spawn gem's usage:

https://github.com/rtomayko/posix-spawn/blob/master/ext/posix-spawn.c#L242-L258

It also appears RTEST(Qundef) returns true, which causes a segfault in posix-spawn gem here:

https://github.com/rtomayko/posix-spawn/blob/master/ext/posix-spawn.c#L425

I think we should revert back to original behavior before 2.2.0 is released.

[tmm1 (Aman Karmani)]

This regression was introduced in r48114 to fix #10413

[tmm1 (Aman Karmani)]

Proposed patch: https://github.com/github/ruby/commit/a2b6dadbabf935ec9126c8bd9210fbb133b55c84.diff

/cc @nobu (Nobuyoshi Nakada)

[nobu (Nobuyoshi Nakada)]

I think a function can tell no keys from deleting nil value, like hash_delete in your patch, is necessary.

[tmm1 (Aman Karmani)]

@nobu (Nobuyoshi Nakada) Do you think we need to change rb_hash_delete behavior? Or do you mean we should add another public c-api function for the undef behavior, like rb_hash_delete_xxx

[ko1 (Koichi Sasada)]

At Comment#3, Nobu said that we still need a function which returns no such entry.

We have three possibility:

(a) reutrn Qundef when no entry (current rb_hash_delete())
(b) return nil when no entry
(c) return passed block results or nil when no entry (previous rb_hash_delete())

So my recommendation is:

(1) Implement (a) with other name (ex: rb_hash_delete_key())
(2) Implement (b) named rb_hash_delete() using (1)
(3) Implement (c) for Hash#delete with (1).

@tmm1 (Aman Karmani): is it okay?

[ko1 (Koichi Sasada)]

How about it?

rb_hash_delete_entry() for (1).

Index: ChangeLog
===================================================================
--- ChangeLog	(revision 48955)
+++ ChangeLog	(working copy)
@@ -1,3 +1,19 @@
+Wed Dec 24 11:24:03 2014  Koichi Sasada  <[e-mail]>
+
+	* hash.c (rb_hash_delete): return Qnil if there are no corresponding
+	  entry. [Bug #10623]
+
+	* hash.c (rb_hash_delete_entry): try delete and return Qundef if there
+	  are no corresponding entry.
+
+	* internal.h: add rb_hash_delete_entry()'s declaration.
+
+	* symbol.c: use rb_hash_delete_entry().
+
+	* thread.c: use rb_hash_delete_entry().
+
+	* ext/-test-/hash/delete.c: use rb_hash_delete_entry().
+
 Wed Dec 24 09:35:11 2014  NAKAMURA Usaku  <[e-mail]>
 
 	* ext/fiddle/extconf.rb: remove ffitarget.h generated by configure on
Index: ext/-test-/hash/delete.c
===================================================================
--- ext/-test-/hash/delete.c	(revision 48955)
+++ ext/-test-/hash/delete.c	(working copy)
@@ -3,7 +3,7 @@
 static VALUE
 hash_delete(VALUE hash, VALUE key)
 {
-    VALUE ret = rb_hash_delete(hash, key);
+    VALUE ret = rb_hash_delete_entry(hash, key);
     return ret == Qundef ? Qnil : rb_ary_new_from_values(1, &ret);
 }
 
Index: hash.c
===================================================================
--- hash.c	(revision 48955)
+++ hash.c	(working copy)
@@ -969,23 +969,49 @@ rb_hash_index(VALUE hash, VALUE value)
     return rb_hash_key(hash, value);
 }
 
+/*
+ * delete a specified entry a given key.
+ * if there is the corresponding entry, return a value of the entry.
+ * if there is no corresponding entry, return Qundef.
+ */
 VALUE
-rb_hash_delete(VALUE hash, VALUE key)
+rb_hash_delete_entry(VALUE hash, VALUE key)
 {
     st_data_t ktmp = (st_data_t)key, val;
 
-    if (!RHASH(hash)->ntbl)
+    if (!RHASH(hash)->ntbl) {
         return Qundef;
-    if (RHASH_ITER_LEV(hash) > 0) {
-	if (st_delete_safe(RHASH(hash)->ntbl, &ktmp, &val, (st_data_t)Qundef)) {
+    }
+    else if (RHASH_ITER_LEV(hash) > 0 &&
+	     (st_delete_safe(RHASH(hash)->ntbl, &ktmp, &val, (st_data_t)Qundef))) {
 	    FL_SET(hash, HASH_DELETED);
 	    return (VALUE)val;
 	}
-    }
-    else if (st_delete(RHASH(hash)->ntbl, &ktmp, &val))
+    else if (st_delete(RHASH(hash)->ntbl, &ktmp, &val)) {
 	return (VALUE)val;
+    }
+    else {
     return Qundef;
 }
+}
+
+/*
+ * delete a specified entry by a given key.
+ * if there is the corresponding entry, return a value of the entry.
+ * if there is no corresponding entry, return Qnil.
+ */
+VALUE
+rb_hash_delete(VALUE hash, VALUE key)
+{
+    VALUE deleted_value = rb_hash_delete_entry(hash, key);
+
+    if (deleted_value != Qundef) { /* likely pass */
+	return deleted_value;
+    }
+    else {
+	return Qnil;
+    }
+}
 
 /*
  *  call-seq:
@@ -1011,13 +1037,20 @@ rb_hash_delete_m(VALUE hash, VALUE key)
     VALUE val;
 
     rb_hash_modify_check(hash);
-    val = rb_hash_delete(hash, key);
-    if (val != Qundef) return val;
+    val = rb_hash_delete_entry(hash, key);
+
+    if (val != Qundef) {
+	return val;
+    }
+    else {
     if (rb_block_given_p()) {
 	return rb_yield(key);
     }
+	else {
     return Qnil;
 }
+    }
+}
 
 struct shift_var {
     VALUE key;
@@ -1063,7 +1096,7 @@ rb_hash_shift(VALUE hash)
 	else {
 	    rb_hash_foreach(hash, shift_i_safe, (VALUE)&var);
 	    if (var.key != Qundef) {
-		rb_hash_delete(hash, var.key);
+		rb_hash_delete_entry(hash, var.key);
 		return rb_assoc_new(var.key, var.val);
 	    }
 	}
Index: internal.h
===================================================================
--- internal.h	(revision 48955)
+++ internal.h	(working copy)
@@ -1119,6 +1119,9 @@ int rb_bug_reporter_add(void (*func)(FIL
 VALUE rb_str_normalize_ospath(const char *ptr, long len);
 #endif
 
+/* hash.c (export) */
+VALUE rb_hash_delete_entry(VALUE hash, VALUE key);
+
 /* io.c (export) */
 void rb_maygvl_fd_fix_cloexec(int fd);
 
Index: symbol.c
===================================================================
--- symbol.c	(revision 48955)
+++ symbol.c	(working copy)
@@ -740,7 +740,7 @@ rb_sym2id(VALUE sym)
 	    RSYMBOL(sym)->id = id |= num;
 	    /* make it permanent object */
 	    set_id_entry(num >>= ID_SCOPE_SHIFT, fstr, sym);
-	    rb_hash_delete(global_symbols.dsymbol_fstr_hash, fstr);
+	    rb_hash_delete_entry(global_symbols.dsymbol_fstr_hash, fstr);
 	}
     }
     else {
Index: thread.c
===================================================================
--- thread.c	(revision 48955)
+++ thread.c	(working copy)
@@ -4806,13 +4806,13 @@ recursive_pop(VALUE list, VALUE obj, VAL
 	    return 0;
 	}
 	if (RB_TYPE_P(pair_list, T_HASH)) {
-	    rb_hash_delete(pair_list, paired_obj);
+	    rb_hash_delete_entry(pair_list, paired_obj);
 	    if (!RHASH_EMPTY_P(pair_list)) {
 		return 1; /* keep hash until is empty */
 	    }
 	}
     }
-    rb_hash_delete(list, obj);
+    rb_hash_delete_entry(list, obj);
     return 1;
 }
 

[ko1 (Koichi Sasada)]

• Status changed from Open to Closed
• % Done changed from 0 to 100

Applied in changeset r48958.

---

• hash.c (rb_hash_delete): return Qnil if there are no corresponding
  entry. [Bug #10623]
• hash.c (rb_hash_delete_entry): try delete and return Qundef if there
  are no corresponding entry.
• internal.h: add rb_hash_delete_entry()'s declaration.
• symbol.c: use rb_hash_delete_entry().
• thread.c: use rb_hash_delete_entry().
• ext/-test-/hash/delete.c: use rb_hash_delete_entry().

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.0.0: UNKNOWN, 2.1: UNKNOWN to 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: REQUIRED

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: REQUIRED to 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: REQUIRED

I didn't confirm it by myyself, but r48114 was already backported into ruby_2_1/ruby_2_0_0. So this should be backported into them too.

[naruse (Yui NARUSE)]

• Backport changed from 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: REQUIRED to 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: DONE

[usa (Usaku NAKAMURA)]

• Related to Bug #10413: Unexpected block invocation with unknown keywords added