[Help-glpk] Re: re-entrant test version of GLPK

[Andrew Makhorin]

Joonas,

Below here is a Win32 thread-safe version of glplib1 I made from your
patch. It is an example of what I meant talking about platform-specific
versions for various platforms. I think it would be much better to
choose an appropriate version of the code in Makefile rather than using
#ifdef programming.

Andrew Makhorin

------------------------------------------------------------------------

/* glplib1.c (Win32 thread-safe version) */

#include <stdio.h>
#include <windows.h>
#include "glplib.h"

static volatile int initialized=0;
static DWORD key=0;
static volatile DWORD l1=0;
static volatile DWORD l2=0;

void initialize_thread_objects_if_needed( void )
{
    while ( initialized )
    {
      /* we could not allocate TslAlloc
       * when the 1st thread was created
       * so we do a little black magic,
       * in order to make an atomic operation
       * without locking primitives, since
       * they are likewise required to
       * be created before threads.
       *
       * I am doing what is called by 2 flag locking.
       */
      DWORD me=GetCurrentThreadId();

      if( l1 == 0)
      {
          l1=me;
          if( l2 == 0 )
          {
              l2= me;
              if( l1 == me)
              {
                  if ( initialized )
                  {   key=TlsAlloc();
                      initialized=1;
                  }
                  l2=0;
                  if( l1 == me)
                      l1=0;
                  break;

              }
               else l2=0; 
          } else
              l1=0;
      }  
      Sleep(0); 
    }
}

void lib_set_ptr(void *ptr)
{
      initialize_thread_objects_if_needed( ) ;
          
     if( TlsSetValue( key , (LPVOID) ptr)== 0 )
     {   printf("Tls write failed !\n");
         exit( 1 );
     }

}

void* lib_get_ptr(void)
{
      void* aa; // (LPVOID)
      initialize_thread_objects_if_needed( ) ;

      aa=TlsGetValue(key );
        return  aa;
}

/* eof */