www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.learn - Access Violation in callback from sort

reply "Jabb" <jj.jabbaloo gmail.com> writes:
Just got the TDPL book and it's a great read! I learn best when 
typing out the code myself, so I decided to make a single VisualD 
project and put the different exercises in separate modules. I am 
having problems with sort in std.algorithms - well, actually it 
appears to be a closure problem when sort calls my delegate.

Here's a sample of the problem - in main.d I have

//------------------
module main;
import std.algorithm;
void main() {
	uint[string] counts = [ "a":4, "b":5, "c":3, "d":1 ];
	string[] keys = counts.keys;

	sort!((a, b) { return counts[a] > counts[b]; })(keys);
}
//------------------

Alone this works just fine. But if I add another file called 
myalgs.d, and put the following in it:

//------------------
module myalgs;
import std.algorithm;
//------------------

Then I get the following exception:

object.Error: Access Violation
----------------
C:\D\dmd2\windows\bin\..\..\src\phobos\std\algorithm.d(7112): 
mainmain__T8sortImplS14main9__lambda3VE3std9algorithm12SwapStrategy0TAAyaZsortImpl
----------------

Steping through the code it appears that the Access Violation 
occurs when accessing counts[a].

I am using DMD32 v2.059; my compilation command line looks like:
dmd -g -debug -X -Xf"$(IntDir)\$(TargetName).json" 
-deps="$(OutDir)\$(ProjectName).dep" 
-of"$(OutDir)\$(ProjectName).exe_cv" -map 
"$(INTDIR)\$(SAFEPROJECTNAME).map" -L/NOMAP

Am I doing something wrong here?

thanks for the help!
May 02 2012
next sibling parent "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Wed, 02 May 2012 11:27:57 -0400, Jabb <jj.jabbaloo gmail.com> wrote:


 Just got the TDPL book and it's a great read! I learn best when typing  
 out the code myself, so I decided to make a single VisualD project and  
 put the different exercises in separate modules. I am having problems  
 with sort in std.algorithms - well, actually it appears to be a closure  
 problem when sort calls my delegate.


There shouldn't be any closure here, sort is not storing the delegate  
pointer.


 Here's a sample of the problem - in main.d I have

 //------------------
 module main;
 import std.algorithm;
 void main() {
 	uint[string] counts = [ "a":4, "b":5, "c":3, "d":1 ];
 	string[] keys = counts.keys;

 	sort!((a, b) { return counts[a] > counts[b]; })(keys);
 }
 //------------------

 Alone this works just fine. But if I add another file called myalgs.d,  
 and put the following in it:

 //------------------
 module myalgs;
 import std.algorithm;
 //------------------

 Then I get the following exception:

 object.Error: Access Violation
 ----------------
 C:\D\dmd2\windows\bin\..\..\src\phobos\std\algorithm.d(7112):  
 mainmain__T8sortImplS14main9__lambda3VE3std9algorithm12SwapStrategy0TAAyaZsortImpl
 ----------------

 Steping through the code it appears that the Access Violation occurs  
 when accessing counts[a].

 I am using DMD32 v2.059; my compilation command line looks like:
 dmd -g -debug -X -Xf"$(IntDir)\$(TargetName).json"  
 -deps="$(OutDir)\$(ProjectName).dep"  
 -of"$(OutDir)\$(ProjectName).exe_cv" -map  
 "$(INTDIR)\$(SAFEPROJECTNAME).map" -L/NOMAP


I can't see any errors, I think this is worthy of a bug report, it's nice  
and small and self-contained.

http://d.puremagic.com/issues

-Steve
May 03 2012
prev sibling next sibling parent reply "Stefan" <stefan.schuerger gmx.de> writes:
On Wednesday, 2 May 2012 at 15:27:58 UTC, Jabb wrote:


 import std.algorithm;
 void main() {
 	uint[string] counts = [ "a":4, "b":5, "c":3, "d":1 ];
 	string[] keys = counts.keys;

 	sort!((a, b) { return counts[a] > counts[b]; })(keys);
 }


Did you try
string[] keys = counts.keys.dup;
?

Sometimes you get weird aliasing issues, as the sort! template
modifies the original array.
Mar 21 2013
parent =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 03/21/2013 01:02 PM, Stefan wrote:

 On Wednesday, 2 May 2012 at 15:27:58 UTC, Jabb wrote:


 import std.algorithm;
 void main() {
 uint[string] counts = [ "a":4, "b":5, "c":3, "d":1 ];
 string[] keys = counts.keys;

 sort!((a, b) { return counts[a] > counts[b]; })(keys);
 }


 Did you try
 string[] keys = counts.keys.dup;
 ?


That should be ok. Unlike .byKey, .keys is eager; all of the keys are in 
the returned slice by the time it returns.

Ali
Mar 21 2013
prev sibling parent =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 05/02/2012 08:27 AM, Jabb wrote:


 Alone this works just fine. But if I add another file called myalgs.d,
 and put the following in it:

 //------------------
 module myalgs;
 import std.algorithm;
 //------------------

 Then I get the following exception:

 object.Error: Access Violation


I can reproduce the bug with 2.062 as well as an earlier development 
build of 2.063 (a fresher dmd does not build at the moment.)

I have found a workaround: Put the second file later in the dmd command 
line:

   dmd main.d myalgs.d

Ali
Mar 21 2013