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digitalmars.D.bugs - A strange bug with using functions as args

reply BCS <BCS_member pathlink.com> writes:
I have run into what I think is a bug.
The code (sort of)

class A
{
int foo(){...}		// always returns the same number (in this case)
int bar(int i) {...}	// returns a function of only i

int runA()
{
return bar(foo());
}

int runB()
{
int i = foo();
return bar(i);
}


}


void main()
{
A a = new A;
writef(a.runA(), \n);
writef(a.runB(), \n);
}


(This code isn't the code with the bug, that code is 15k+ lines long.)

The bug: A.runA and A.runB return different numbers.
In my actual code storing the function to a temp variable and using that changed
the output.
Any ideas??
Sep 15 2005
next sibling parent reply Hasan Aljudy <hasan.aljudy gmail.com> writes:
This doesn't help much, I tried the following (see below) and it worked 
fine.
Maybe it's what the function bar is doing in your code ..

Could you try to provide a more specific test case?

This works fine:
----------------------------------------
import std.stdio;

class A
{
     int foo(){ return 5; }
     int bar(int i) { return i + 1; }

     int runA()
     {
         return bar(foo());
     }

     int runB()
     {
         int i = foo();
         return bar(i);
     }
}


void main()
{
     A a = new A;
     writef(a.runA(), \n);
     writef(a.runB(), \n);
}

BCS wrote:

 I have run into what I think is a bug.
 The code (sort of)
 
 class A
 {
 int foo(){...}		// always returns the same number (in this case)
 int bar(int i) {...}	// returns a function of only i
 
 int runA()
 {
 return bar(foo());
 }
 
 int runB()
 {
 int i = foo();
 return bar(i);
 }
 
 
 }
 
 
 void main()
 {
 A a = new A;
 writef(a.runA(), \n);
 writef(a.runB(), \n);
 }
 
 
 (This code isn't the code with the bug, that code is 15k+ lines long.)
 
 The bug: A.runA and A.runB return different numbers.
 In my actual code storing the function to a temp variable and using that
changed
 the output.
 Any ideas??
Sep 15 2005
parent BCS <BCS_member pathlink.com> writes:
I'll try to strip it down but don't hold you'r breath. It's quite involved code.


In article <dgci00$1u4p$1 digitaldaemon.com>, Hasan Aljudy says...

This doesn't help much, I tried the following (see below) and it worked 
fine.
Maybe it's what the function bar is doing in your code ..

Could you try to provide a more specific test case?

This works fine:
----------------------------------------
import std.stdio;

class A
{
     int foo(){ return 5; }
     int bar(int i) { return i + 1; }

     int runA()
     {
         return bar(foo());
     }

     int runB()
     {
         int i = foo();
         return bar(i);
     }
}


void main()
{
     A a = new A;
     writef(a.runA(), \n);
     writef(a.runB(), \n);
}

BCS wrote:

 I have run into what I think is a bug.
 The code (sort of)
 
 class A
 {
 int foo(){...}		// always returns the same number (in this case)
 int bar(int i) {...}	// returns a function of only i
 
 int runA()
 {
 return bar(foo());
 }
 
 int runB()
 {
 int i = foo();
 return bar(i);
 }
 
 
 }
 
 
 void main()
 {
 A a = new A;
 writef(a.runA(), \n);
 writef(a.runB(), \n);
 }
 
 
 (This code isn't the code with the bug, that code is 15k+ lines long.)
 
 The bug: A.runA and A.runB return different numbers.
 In my actual code storing the function to a temp variable and using that
changed
 the output.
 Any ideas??
Sep 15 2005
prev sibling parent reply Stewart Gordon <smjg_1998 yahoo.com> writes:
BCS wrote:
<snip>

 (This code isn't the code with the bug, that code is 15k+ lines long.)




If this code doesn't have the bug, then why did you post it?

A good idea is to try first to reproduce the bug by writing a short 
program from scratch.  Then, if that fails, then try trimming your 
program down.

This might help you:

http://www.physci.org/codes/sscce.jsp

(It's actually aimed at being a technique for isolating bugs in your 
programs, but many of the points are also applicable to writing compiler 
bug testcases.)

Stewart.

-- 
-----BEGIN GEEK CODE BLOCK-----
Version: 3.1
GCS/M d- s:- C++  a->--- UB  P+ L E  W++  N+++ o K-  w++  O? M V? PS- 
PE- Y? PGP- t- 5? X? R b DI? D G e++>++++ h-- r-- !y
------END GEEK CODE BLOCK------

My e-mail is valid but not my primary mailbox.  Please keep replies on 
the 'group where everyone may benefit.
Sep 16 2005
parent BCS <BCS_member pathlink.com> writes:
I posted that code because it gives general idea of what the bug is in the hope
that someone would recognize it a similar to something they had encountered. I
plan to try to strip down the real code but I expect it will not be vary
fruitful. My best guess is that it is a compiler bug (or something that will
make me feel vary stupid) or some such thing. 

Below is a better approximation of the real code. (This actually does a simpler
case of  what the real thing does.) In the real thing, on line 6, storing the
value of the 2nt argument to a temp variable before the call changes how things
run.

This code also doesn’t have the bug. (Sorry)

#import std.math;
#import std.stdio;

#class Taylor
#{
#	void regen(real time)	{n = newInert(n.P(time), n.V(time));}	//line 6
#	real P(real time)	{ return n.P(time); }

#	static Newton newInert(real p, real v)
#				{ return new Newton(p, v, Acc(p), Jrk(p)); }

#	static real Acc(real p)	{ return -p; }
#	static real Jrk(real p) { return -sqrt(1 - p*p); }

#	Newton n;

#}

#class Newton
#{
#	this(real nP, real nV, real nA, real nJ)
#	{
#		p=nP;	v=nV;	a=nA;	j=nJ;
#		writef("%g %g %g %g \n", p, v, a, j);
#	}

#	real P(real time) { return p + v*time + a*(time*time/2) +
j*(time*time*time/6); }
#	real V(real time) { return v + a*time + j*(time*time/2); }

#	real p;
#	real v;
#	real a;
#	real j;
#}

#void main()
#{
#	Taylor t = new Taylor;

#	t.n = Taylor.newInert(.999, 0);
#	for(int i=0; i< 26; i++)
#		t.regen(.1);
#}

One candidate for a cause is that the compiler Is inlineing the calls at line 6
and time is getting changed some where in the first call.



In article <dgf13m$1a2m$1 digitaldaemon.com>, Stewart Gordon says...

If this code doesn't have the bug, then why did you post it?

A good idea is to try first to reproduce the bug by writing a short 
program from scratch.  Then, if that fails, then try trimming your 
program down.

This might help you:

http://www.physci.org/codes/sscce.jsp

(It's actually aimed at being a technique for isolating bugs in your 
programs, but many of the points are also applicable to writing compiler 
bug testcases.)

Stewart.

-- 
-----BEGIN GEEK CODE BLOCK-----
Version: 3.1
GCS/M d- s:- C++  a->--- UB  P+ L E  W++  N+++ o K-  w++  O? M V? PS- 
PE- Y? PGP- t- 5? X? R b DI? D G e++>++++ h-- r-- !y
------END GEEK CODE BLOCK------

My e-mail is valid but not my primary mailbox.  Please keep replies on 
the 'group where everyone may benefit.
Sep 16 2005