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digitalmars.D.learn - Strange error with templates and inheritance.

reply Frank Fischer <frank.fischer s2001.tu-chemnitz.de> writes:
Hi,

i'm currently developing a library and I heavily use templates and multiple
inheritance (of interfaces, of course). The following inheritance structure
is used (I removed all methods that are not important to show the error):

---
module mytest;

import std.stdio;

interface A(T) {
    C!(T) func();
    size_t f();
}

abstract class B(T): A!(T) {
}

interface C(T): A!(T) {
}

class D: B!(int), C!(int) {
    size_t f() { return 42; }
    C!(int) func() { return this; }
}

void main() {
    A!(int) x = new D();
    writefln("%d", x.f());
}
---

When I compile this snippet with dmd 2.003 on my linux-box, I get a
segmentation fault on the call "x.f()" in the last line. Furthermore, if I
use an interface instead of an abstract class for B, everything is fine.
Even if I just change the order of definition of 'func' and 'f' in A, i.e.

interface A(T) {
    size_t f();
    C!(T) func();
}

everything works. 

Can anyone reproduce this error and/or explain it? In my library I
can't/want to change B into an interface, because the class should contain
some methods.

Thanks,
Frank
Aug 04 2007
parent reply Robert Fraser <fraserofthenight gmail.com> writes:
Frank Fischer Wrote:

 Hi,
 
 i'm currently developing a library and I heavily use templates and multiple
 inheritance (of interfaces, of course). The following inheritance structure
 is used (I removed all methods that are not important to show the error):
 
 ---
 module mytest;
 
 import std.stdio;
 
 interface A(T) {
     C!(T) func();
     size_t f();
 }
 
 abstract class B(T): A!(T) {
 }
 
 interface C(T): A!(T) {
 }
 
 class D: B!(int), C!(int) {
     size_t f() { return 42; }
     C!(int) func() { return this; }
 }
 
 void main() {
     A!(int) x = new D();
     writefln("%d", x.f());
 }
 ---
 
 When I compile this snippet with dmd 2.003 on my linux-box, I get a
 segmentation fault on the call "x.f()" in the last line. Furthermore, if I
 use an interface instead of an abstract class for B, everything is fine.
 Even if I just change the order of definition of 'func' and 'f' in A, i.e.
 
 interface A(T) {
     size_t f();
     C!(T) func();
 }
 
 everything works. 
 
 Can anyone reproduce this error and/or explain it? In my library I
 can't/want to change B into an interface, because the class should contain
 some methods.
 
 Thanks,
 Frank
 

Sounds like a bug. You have your minimal code sample there, report it.
Aug 04 2007
parent reply Ary Manzana <ary esperanto.org.ar> writes:
Robert Fraser escribió:
 Frank Fischer Wrote:
 
 Hi,

 i'm currently developing a library and I heavily use templates and multiple
 inheritance (of interfaces, of course). The following inheritance structure
 is used (I removed all methods that are not important to show the error):

 ---
 module mytest;

 import std.stdio;

 interface A(T) {
     C!(T) func();
     size_t f();
 }

 abstract class B(T): A!(T) {
 }

 interface C(T): A!(T) {
 }

 class D: B!(int), C!(int) {
     size_t f() { return 42; }
     C!(int) func() { return this; }
 }

 void main() {
     A!(int) x = new D();
     writefln("%d", x.f());
 }
 ---

 When I compile this snippet with dmd 2.003 on my linux-box, I get a
 segmentation fault on the call "x.f()" in the last line. Furthermore, if I
 use an interface instead of an abstract class for B, everything is fine.
 Even if I just change the order of definition of 'func' and 'f' in A, i.e.

 interface A(T) {
     size_t f();
     C!(T) func();
 }

 everything works. 

 Can anyone reproduce this error and/or explain it? In my library I
 can't/want to change B into an interface, because the class should contain
 some methods.

 Thanks,
 Frank

Sounds like a bug. You have your minimal code sample there, report it.

Yes, it sounds like a bug to me too. I tried to debug the code and x.f() leads to D.func(), and then it crashes. Further, in the access violation exception the function _d_invariant in module invariant.d (phobos/internal) is named.
Aug 04 2007
parent Manfred Nowak <svv1999 hotmail.com> writes:
Ary Manzana wrote

 I tried to debug the code and x.f() 
 leads to D.func(), and then it crashes.

This throws some light into the matter. In fact, I have reported an analogue "feature" before, but all I got was a remark that it has to be this way, because D is a system programming language. -manfred
Aug 04 2007