  TT_Load_Context( TT_ExecContext  exec,
                   TT_Face         face,
                   TT_Size         size )
  {
    FT_Int          i;
    FT_ULong        tmp;
    TT_MaxProfile*  maxp;
    FT_Error        error;


    exec->face = face;
    maxp       = &face->max_profile;
    exec->size = size;

    if ( size )
    {
      exec->numFDefs   = size->num_function_defs;
      exec->maxFDefs   = size->max_function_defs;
      exec->numIDefs   = size->num_instruction_defs;
      exec->maxIDefs   = size->max_instruction_defs;
      exec->FDefs      = size->function_defs;
      exec->IDefs      = size->instruction_defs;
      exec->pointSize  = size->point_size;
      exec->tt_metrics = size->ttmetrics;
      exec->metrics    = *size->metrics;

      exec->maxFunc    = size->max_func;
      exec->maxIns     = size->max_ins;

      for ( i = 0; i < TT_MAX_CODE_RANGES; i++ )
        exec->codeRangeTable[i] = size->codeRangeTable[i];

      /* set graphics state */
      exec->GS = size->GS;

      exec->cvtSize = size->cvt_size;
      exec->cvt     = size->cvt;

      exec->storeSize = size->storage_size;
      exec->storage   = size->storage;

      exec->twilight  = size->twilight;

      /* In case of multi-threading it can happen that the old size object */
      /* no longer exists, thus we must clear all glyph zone references.   */
      FT_ZERO( &exec->zp0 );
      exec->zp1 = exec->zp0;
      exec->zp2 = exec->zp0;
    }

    /* XXX: We reserve a little more elements on the stack to deal safely */
    /*      with broken fonts like arialbs, courbs, timesbs, etc.         */
    tmp = (FT_ULong)exec->stackSize;
    error = Update_Max( exec->memory,
                        &tmp,
                        sizeof ( FT_F26Dot6 ),
                        (void*)&exec->stack,
                        maxp->maxStackElements + 32 );
    exec->stackSize = (FT_Long)tmp;
    if ( error )
      return error;

    tmp = exec->glyphSize;
    error = Update_Max( exec->memory,
                        &tmp,
                        sizeof ( FT_Byte ),
                        (void*)&exec->glyphIns,
                        maxp->maxSizeOfInstructions );
    exec->glyphSize = (FT_UShort)tmp;
    if ( error )
      return error;

    exec->pts.n_points   = 0;
    exec->pts.n_contours = 0;

    exec->zp1 = exec->pts;
    exec->zp2 = exec->pts;
    exec->zp0 = exec->pts;

    exec->instruction_trap = FALSE;

    return FT_Err_Ok;
  }

The product dereferences a pointer that it expects to be valid but is NULL.