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Bug #2545

closed

Array#delete_if is borked if user calls 'break'

Added by candlerb (Brian Candler) about 14 years ago. Updated over 12 years ago.

Status:
Closed
Target version:
-
ruby -v:
ruby 1.8.7 (2009-06-12 patchlevel 174) [x86_64-linux]
Backport:
[ruby-core:27366]

Description

=begin
Array is corrupted if you break out of a delete_if { ... } loop. I would expect that the elements already marked as deleted would be deleted, and the remainder of the array would be unchanged.

a = [5,6,7,8,9,10]
=> [5, 6, 7, 8, 9, 10]
a.delete_if { |x| break if x > 8; x < 7 }
=> nil
a
=> [7, 8, 7, 8, 9, 10]

RUBY_VERSION
=> "1.8.7"
RUBY_PATCHLEVEL
=> 174
=end


Related issues 2 (0 open2 closed)

Related to Ruby master - Bug #10722: Array#keep_if is borked if user calls 'break'Closed01/09/2015Actions
Related to Ruby master - Feature #10714: Array#reject! nonlinear performance problemClosedakr (Akira Tanaka)01/08/2015Actions
Actions #1

Updated by nobu (Nobuyoshi Nakada) about 14 years ago

Hi,

At Sat, 2 Jan 2010 05:55:00 +0900,
Brian Candler wrote in [ruby-core:27366]:

Array is corrupted if you break out of a delete_if { ... }
loop. I would expect that the elements already marked as
deleted would be deleted, and the remainder of the array
would be unchanged.

The behavior would be an implementation detail, and should be
undefined (or implementation defined), I guess.

Index: array.c
===================================================================
--- array.c	(revision 26229)
+++ array.c	(working copy)
@@ -2307,7 +2307,18 @@ rb_ary_reject_bang(VALUE ary)
     for (i1 = i2 = 0; i1 < RARRAY_LEN(ary); i1++) {
 	VALUE v = RARRAY_PTR(ary)[i1];
-	if (RTEST(rb_yield(v))) continue;
 	if (i1 != i2) {
+	    int state = 0;
+	    if (RTEST(rb_protect(rb_yield, v, &state))) continue;
 	    rb_ary_store(ary, i2, v);
+	    if (state) {
+		VALUE *ptr = RARRAY_PTR(ary);
+		long len = RARRAY_LEN(ary);
+		MEMCPY(ptr + i2 + 1, ptr + i1 + 1, VALUE, len - i1 - 1);
+		ARY_SET_LEN(ary, len - i1 + i2);
+		rb_jump_tag(state);
+	    }
+	}
+	else {
+	    if (RTEST(rb_yield(v))) continue;
 	}
 	i2++;

--
Nobu Nakada

Actions #2

Updated by shyouhei (Shyouhei Urabe) about 14 years ago

  • Status changed from Open to Assigned
  • Assignee set to matz (Yukihiro Matsumoto)

I don't think so. I'd also expect as the reporter did. Isn't it a bug?

Assigning to matz because this can be a design issue.

Updated by daz (Dave B) over 12 years ago

Just met this problem:
ruby 1.8.7 (2011-02-18 patchlevel 334) [i386-mingw32]

I'd also consider it a bug and that the ruby implementation should be hidden from the user. Once an element has been selected for deletion, at the end of this iteration, it should be expected to be gone. When using very large arrays, where the programmer knows of a shortcut (e.g. the rest of the array need not be considered), s/he should be encouraged to handle it with 'break'. In testing, I was left wondering whether 'delete_if' was non-destructive, because nothing had changed, and started looking for a bang! method.
To achieve the current behaviour, I only need an Array#dup above the loop.

Thanks to Nobu for working a patch.

daz

Actions #4

Updated by nobu (Nobuyoshi Nakada) over 12 years ago

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

This issue was solved with changeset r32360.
Brian, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.


  • array.c (rb_ary_reject_bang, rb_ary_delete_if): rejected
    elements should be removed. fixed [Bug #2545]
Actions #5

Updated by nobu (Nobuyoshi Nakada) over 12 years ago

  • Project changed from Ruby 1.8 to Ruby master
  • Category changed from core to core
  • Target version deleted (Ruby 1.8.7)

Updated by nagachika (Tomoyuki Chikanaga) over 12 years ago

Hi,

According to test added by r32360,

a = [ 5, 6, 7, 8, 9, 10 ]
a.delete_if {|i| break i if i > 8; i < 7}

it results
a # => [7, 8]

But I feel it could be [7, 8, 9, 10] because block didn't return true for 9, 10.
Matz, How do you think about it?

Updated by wanabe (_ wanabe) about 9 years ago

  • Related to Bug #10722: Array#keep_if is borked if user calls 'break' added

Updated by nobu (Nobuyoshi Nakada) about 9 years ago

  • Related to Feature #10714: Array#reject! nonlinear performance problem added
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