http://d.puremagic.com/issues/show_bug.cgi?id=1084

           Summary: lazy variadic parameters break in strange way
           Product: D
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P3
         Component: DMD
        AssignedTo: bugzilla@digitalmars.com
        ReportedBy: default_357-line@yahoo.de


Consider the following code.

import std.stdio;
char[] test() { writefln("Eval test"); return "bla"; }
void test2(lazy char[][] bla ...) { foreach (elem; bla) writefln(elem);}
void main() { test2(test, test); }

It compiles (verified gdc .21/dmd .175 by h3 [I couldn't find anybody with 1.010; volunteers appreciated]), but when run, outputs

Eval test
Eval test
bla
<garbage>

Some observations:
 - returning "bla".dup doesn't help.
 - The garbage seems to be an array with the same length as whatever was
returned from test. I did not check to see where the pointer goes. Maybe that
might offer some clue.

If this has already been fixed in 1.010, sorry for wasting your time. greetings&stuffies --downs


-- 

http://d.puremagic.com/issues/show_bug.cgi?id=1084





------- Comment #1 from fvbommel@wxs.nl  2007-03-28 14:57 -------
What seems to be happening here:
The parameter list of test2 is "lazy char[][] bla ...".
The type of the parameter is an array of char[]s. Because of the "..." this
array is implicitly constructed on the stack when the function is called.
However, because of the "lazy" this implicitly construction is put into a
delegate that is then pushed onto the stack as the actual parameter.
The problem with this is that the delegate constructs an array on the stack and
then returns _that_ array.
So the "lazy" delegate is returning a reference to data on the stack (in it's
own stack-frame). This is always a Bad Idea.

(I guess combining "lazy" and "..." is not a good idea)

What you may have meant was:
---
/// A call constructs an array on the stack and pass a reference.
/// Passed "parameters" are evaluated before calling.
void test2(char[][] bla ...) {
        foreach (elem; bla) writefln(elem);
}
---
or:
---
/// A call constructs an array of delegates on the stack and pass a reference
to that.
/// Passed "parameters" aren't evaluated until used.
void test2(char[] delegate()[] bla ...) {
        foreach (elem; bla) writefln(elem());
}
---


-- 

http://d.puremagic.com/issues/show_bug.cgi?id=1084


thomas-dloop@kuehne.cn changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|unspecified                 |1.010




------- Comment #2 from thomas-dloop@kuehne.cn  2007-04-04 15:36 -------
Added to DStress as http://dstress.kuehne.cn/run/l/lazy_03_A.d http://dstress.kuehne.cn/run/l/lazy_03_B.d http://dstress.kuehne.cn/run/l/lazy_03_C.d http://dstress.kuehne.cn/run/l/lazy_03_D.d


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http://d.puremagic.com/issues/show_bug.cgi?id=1084


Don <clugdbug@yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|wrong-code                  |accepts-invalid
                 CC|                            |clugdbug@yahoo.com.au




--- Comment #3 from Don <clugdbug@yahoo.com.au>  2009-08-04 07:31:14 PDT ---
This isn't wrong-code, the bug is in the user's code. Changing to
accepts-invalid.
(Perhaps lazy []... should be illegal?)

On DMD2, it displays:
bug(12): Error: escaping reference to local __arrayArg502
So it's a D1-only issue.

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