Need some help with this...

[Jason House]

Object destructors can be tricky in a GC'd language. It looks like you're accessing a deallocated pointer in your destructor. Order of collection/destruction is not guaranteed.

Bane Wrote:

> Following code will freeze app on std.gc.fullCollect(), when sqlite3_close() in destructor is called. If destructor is called manualy, everything goes ok.
> 
> Is it a bug, and if is, with what? It behaves same on winxp64 and centos5.2 using dmd 1.30 and sqlite 3.6.5 or 3.6.19 statically import lib. Libraries are tested so I do not suspect problem lies in them (they are compiled with dmc/gcc using full threading support).
> 
> Is this some problem with GC or, more likely, my knowledge? I would appreciate some clarification, this thing took me a lot of hours to track.
> 
> Thanks, 
> Bane
> 
> ==========================================
> 
> 
> import std.stdio;
> import std.gc;
> import std.string;
> import std.thread;
> 
> pragma(lib, "sqlite3.lib");
> const int SQLITE_OK = 0;	// Successful result.
> struct sqlite3 {}
> extern(C) int sqlite3_open (char* filename, sqlite3** database);
> extern(C) int sqlite3_close(sqlite3* database);
> 
> class SQLite {
>   sqlite3* h;
>   this(){
>     assert(sqlite3_open(toStringz(":memory:"), &h) == SQLITE_OK);
>   }
>   ~this(){
>     writefln("~this start"); // to help debug
>     assert(sqlite3_close(h) == SQLITE_OK);
>     writefln("~this stop"); // to help debug
>   }
> }
> 
> class T : Thread {
>   int run(){
>     SQLite s = new SQLite;
>     // if next line is uncommented then app wont freeze
>     // delete s;
>     return 0;
>   }
> }
> 
> void main(){
>   while(true){
>     T t = new T;
>     t.start;
>     writefln(Thread.nthreads);
>     if(Thread.nthreads > 10)
>       fullCollect; // this will freeze app
>   }
> }