• Peter Thomassen (23/23) Aug 14 2006 Hi there,
• Kirk McDonald (14/44) Aug 14 2006 In your code. :-) Structs are a value type. Your main() should look like...
• BCS (8/53) Aug 15 2006 If you want to use a pointer-to-List, assign something to it.

Peter Thomassen <info peter-thomassen.de> writes:

Hi there,

I'm coming from PHP and am very new to compiled languages, so maybe I'm
completely wrong.

I have the following bitsort.d:

import std.stdio;
struct List {
        uint value;
}
void main() {
        List* list;
        writefln("This is shown.");
        list.value = 5;
        writefln("This is not shown.");
}

And this happens:

peter tux ~/D $ dmd bitsort.d
gcc bitsort.o -o bitsort -m32 -lphobos -lpthread -lm
peter tux ~/D $ ./bitsort
This is shown.
Segmentation fault (core dumped)
peter tux ~/D $ 


Is this a bug?
Peter

Kirk McDonald <kirklin.mcdonald gmail.com> writes:

Peter Thomassen wrote:
 Hi there,
 
 I'm coming from PHP and am very new to compiled languages, so maybe I'm
 completely wrong.
 
 I have the following bitsort.d:
 
 import std.stdio;
 struct List {
         uint value;
 }
 void main() {
         List* list;
         writefln("This is shown.");
         list.value = 5;
         writefln("This is not shown.");
 }
 
 And this happens:
 
 peter tux ~/D $ dmd bitsort.d
 gcc bitsort.o -o bitsort -m32 -lphobos -lpthread -lm
 peter tux ~/D $ ./bitsort
 This is shown.
 Segmentation fault (core dumped)
 peter tux ~/D $ 
 
 
 Is this a bug?
 Peter

In your code. :-) Structs are a value type. Your main() should look like 
this:

void main() {
     List list;
     list.value = 5;
}

By saying "List* list;" you are declaring a pointer to a list, which is 
initialized to null. When you then say "list.value", you're 
dereferencing a null pointer, which causes the segfault.

-- 
Kirk McDonald
Pyd: Wrapping Python with D
http://pyd.dsource.org

BCS <BCS pathlink.com> writes:

Kirk McDonald wrote:
 Peter Thomassen wrote:
 
 Hi there,

 I'm coming from PHP and am very new to compiled languages, so maybe I'm
 completely wrong.

 I have the following bitsort.d:

 import std.stdio;
 struct List {
         uint value;
 }
 void main() {
         List* list;
         writefln("This is shown.");
         list.value = 5;
         writefln("This is not shown.");
 }

 And this happens:

 peter tux ~/D $ dmd bitsort.d
 gcc bitsort.o -o bitsort -m32 -lphobos -lpthread -lm
 peter tux ~/D $ ./bitsort
 This is shown.
 Segmentation fault (core dumped)
 peter tux ~/D $

 Is this a bug?
 Peter

 
 
 In your code. :-) Structs are a value type. Your main() should look like 
 this:
 
 void main() {
     List list;
     list.value = 5;
 }
 
 By saying "List* list;" you are declaring a pointer to a list, which is 
 initialized to null. When you then say "list.value", you're 
 dereferencing a null pointer, which causes the segfault.
 


If you want to use a pointer-to-List, assign something to it.

void main() {
     List back;
     List* list = new List;

     //or      List* list = &back;

     list.value = 5;
}