• ted (22/22) Aug 13 2015 Hi,
• Xinok (9/32) Aug 14 2015 I can confirm that this is a bug but I'm not sure what the
• anonymous (5/13) Aug 14 2015 Other insert* functions call the private function
• Xinok (4/8) Aug 14 2015 I would do the null check in the insert* functions themselves.
• anonymous (5/13) Aug 15 2015 https://github.com/D-Programming-Language/phobos/pull/3557 may be

ted <foo bar.com> writes:

Hi,

(earlier posting on D.learn, but better test included here)...


dmd.2.067, dmd.2068 (64bit linux)


import std.container: SList;

void main()
{
    SList!int tmp=( 4 );
    SList!int tmp1;

    // Ensure tmp is empty
    tmp.removeAny();
    assert( tmp.empty == true );

    // Both tmp and tmp1 are empty
    // (however tmp1 is not internally initialised)
    tmp.insertAfter( tmp[], 3 );
//    tmp1.insertAfter( tmp1[], 3 );	<====== asserts here.

}

core.exception.AssertError std/container/slist.d(57): Assertion failure

Changes in phobos mean that you cannot append to an _uninitialised_ empty 
singly linked list (you can, however, append to an _initialised_ empty 
linked list.....

bug ?

--ted

"Xinok" <xinok live.com> writes:

On Friday, 14 August 2015 at 06:44:53 UTC, ted wrote:
 Hi,

 (earlier posting on D.learn, but better test included here)...


 dmd.2.067, dmd.2068 (64bit linux)


 import std.container: SList;

 void main()
 {
     SList!int tmp=( 4 );
     SList!int tmp1;

     // Ensure tmp is empty
     tmp.removeAny();
     assert( tmp.empty == true );

     // Both tmp and tmp1 are empty
     // (however tmp1 is not internally initialised)
     tmp.insertAfter( tmp[], 3 );
 //    tmp1.insertAfter( tmp1[], 3 );	<====== asserts here.

 }

 core.exception.AssertError std/container/slist.d(57): Assertion 
 failure

 Changes in phobos mean that you cannot append to an 
 _uninitialised_ empty singly linked list (you can, however, 
 append to an _initialised_ empty linked list.....

 bug ?

 --ted

I can confirm that this is a bug but I'm not sure what the 
"correct" way is to fix it. SList creates a dummy node for the 
root of the list, but because structs don't allow default 
constructors, this dummy node is never allocated in the first 
case. Either we can add lots of null checks to initialize the 
list, or we can add this line:

 disable this();

Thoughts?

"anonymous" <a b.cd> writes:

On Friday, 14 August 2015 at 16:28:39 UTC, Xinok wrote:
 I can confirm that this is a bug but I'm not sure what the 
 "correct" way is to fix it. SList creates a dummy node for the 
 root of the list, but because structs don't allow default 
 constructors, this dummy node is never allocated in the first 
 case. Either we can add lots of null checks to initialize the 
 list, or we can add this line:

  disable this();

 Thoughts?

Other insert*  functions call the private function 
SList.initialize() which does the null-check for _root. I am 
working on a PR adding the missing call in insertAfter - that's a 
1 line change. I am not a phobos dev.

"Xinok" <xinok live.com> writes:

On Friday, 14 August 2015 at 18:12:42 UTC, anonymous wrote:
 Other insert*  functions call the private function 
 SList.initialize() which does the null-check for _root. I am 
 working on a PR adding the missing call in insertAfter - that's 
 a 1 line change. I am not a phobos dev.

I would do the null check in the insert* functions themselves. 
Otherwise, you have the overhead of a function call, assuming the 
function isn't inlined.

"anonymous" <a b.cd> writes:

On Friday, 14 August 2015 at 19:44:17 UTC, Xinok wrote:
 On Friday, 14 August 2015 at 18:12:42 UTC, anonymous wrote:
 Other insert*  functions call the private function 
 SList.initialize() which does the null-check for _root. I am 
 working on a PR adding the missing call in insertAfter - 
 that's a 1 line change. I am not a phobos dev.

 I would do the null check in the insert* functions themselves. 
 Otherwise, you have the overhead of a function call, assuming 
 the function isn't inlined.

https://github.com/D-Programming-Language/phobos/pull/3557 may be 
a better place to discuss this.
Note: I have not the knowledge to look at disassembly and to 
figure out whether dmd inlined a function call or not.