Harbour/xharbour Diff : 8/57 - DETACHED LOCALS AND REFERENCES by Przemyslaw Czerpak

When local variables are used in codeblocks then it's possible that
the codeblocks will exist after leaving the function when they were
created. It's potentially very serious problem which have to be resolved
to avoid internal VM structure corruption. In Clipper, Harbour and
xHarbour special mechanism is used in such situation. Local variables
are "detached" from VM stack so they are still accessible after leaving
the function, f.e.:
      proc make_cb()
         local n := 123
         return {|| ++n  }
We call such variables "detached locals".
Here there are two important differences between Clipper and [x]Harbour.
In Clipper variables are detached when function exits (returns) and it
does not know which variables were used but simply detach whole local
variable frame from VM stack. It's very important to know that because
it can be source of serious memory problems in OS like DOS.
This simple code illustrates it:

      // link using RTLINK and run with //e:0 //swapk:0
      // repeat test second time with additional non empty parameter 
      #define N_LOOPS 15
      #xcommand FREE MEMORY => ? 'free memory: ' + ;
                                 AllTrim( Str( Memory( 104 ) ) )
      proc main( x )
         local n, a
         a := array( N_LOOPS )
         FREE MEMORY
         for n := 1 to N_LOOPS
            a[n] := f( x )
            FREE MEMORY
         next
      return
      func f(x)
         local cb, tmp, ref
         tmp := space( 60000 )
         if empty( x )
            cb := {|| .t. }
         else
            cb := {|| ref }
         endif
      return cb

If you execute above program with non empty parameter then 'tmp' variable
is detached with codeblock which uses 'ref' variable and not released as
long as codeblock is still accessible. It means that in few iterations
all memory are allocated and program crashes. Clipper's programmers should
know that and be careful when use detached local and if necessary clear
explicitly other local variables before returning from the function by
setting NIL to them.
In Harbour and xHarbour only variables explicitly used in codeblocks
are detached and detaching is done when codeblock is created and original
local variables are replaced by references. It is possible because Harbour
and xHarbour support multilevel references chains so it works correctly
also for local parameters passed be reference from parent functions.
In Clipper only one level references are supported what creates second
important differences. When Clipper detaches frame with local parameters
then it has to unreference all existing references breaking them. This code
illustrates it:

      proc main()
         local cb, n := 100
         mk_block( @cb, @n )
         ? "after detaching:"
         ? eval( cb ), n
      return
      proc mk_block( cb, n )
         n := 100
         cb := {|| ++n }
         ? "before detaching:"
         ? eval( cb ), n
      return

Above code compiled by Clipper shows:

      before detaching:
             101        101
      after detaching:
             102        101

so after detaching the references to 'n' variable is broken and codeblocks
access his own copy of this variables.
In Harbour it works correctly so the results are correct and it shows:

      before detaching:
             101        101
      after detaching:
             102        102

In xHarbour ( for unknown to me reasons ) Clipper bug is explicitly emulated
though it was possible to fix it because xHarbour inherited from Harbour
the same early detaching mechanism with multilevel references so just like
in Clipper xHarbour programmers have to carefully watch for possibly broken
references by detached locals and add workarounds for it if necessary.

Harbour/xharbour Diff : 7/57 - PASSING OBJECT VARIABLES BY REFERENCEby Przemyslaw Czerpak

Both compilers support passing object variables by reference though this functionality in xHarbour 

is limited to pure instance or class variables only and does not work for SETGET methods. 

In Harbour it works correctly.

This code illustrates the problem:

      proc main()
         local oBrw := tbrowseNew()
         ? oBrw:autoLite
         oBrw:autoLite := !oBrw:autoLite
         ?? "=>", oBrw:autoLite
         p( @oBrw:autoLite )
         ?? "=>", oBrw:autoLite

      proc p( x )
         x := !x

Harbour prints:
      .T.=> .F.=> .T.
but xHarbour prints:
      .T.=> .F.=> .F.
without generating any compile or run time errors.

HMG.3.0.36 is now Compatible with HB 2.1rc2

CCH : Thanx to Rathi from the HMG Forum, HMG 3.0.36 can now be compiled with Harbour 2.1 rc2 Code: - HMG 3.0.36 (Test) 2011/03/19 Changelog:    - Built using latest Harbour Nightly Build (2011/03/16)    - Following Modifications done on official HMG 3.0.35      * Edit in \hmg\source\c_media.c - Replace line no. 144 with the following:      //    hwnd=MCIWndCreate((HWND) hb_parnl(1),NULL,Style,hb_parc(2));      * Edit in \hmg\source\h_init.prg - Replace line no. 628 with the following:          _HMG_SYSDATA [ 306 ] := ( EMPTY( CreateMutex( , .T., strtran(GetProgramFileName(),'\','_') ) ) .OR. (HMGGetLastError() > 0) )      * Edit in \hmg\source\c_winapimisc.c - Replace line no. 416 to 419 with the following:       HB_FUNC ( HMGGETLASTERROR )       {         hb_retnl( (LONG) GetLastError() ) ;       }      * Edit in \hmg\source\h_windows.prg. Replace line no 5588 with the following:             uResult := CallDll32 ( "IsAppThemed" , "UXTHEME.DLL"  )    - Changed HMG Build system to hbmk2 by adapting HMG 4 and latest Harbour method.    - Changed HMG Build Application System by adapting HMG 4. Please make use of newbuild.bat in samples folder or buildapp.bat in hmg main folder.

Tutorial QT & Harbour Rev. [964] (new link)

CCH : From the harbour-Developers Forum

Hi
The rev. [964] of the tutorial is available at:
http://www.gruppoeratostene.com/harbour/hbqt-tutorial.htm

Regards
Giovanni Di Maria


P.S.
There is a VERY IMPORTANT topic at page 78, about a functional form
created by QT Creator.
Giovanni

Harbour/xharbour Diff : 6/57 - PASSING ARRAY AND HASH ITEMS BY REFERENCE by Przemyslaw Czerpak

### PASSING ARRAY AND HASH ITEMS BY REFERENCE ###
=======================================================
Harbour supports passing array and hash items by reference, f.e.:
proc main()
local aVal := { "abc", "klm", "xyz" }, ;
hVal := { "qwe"=>"123", "asd"=>"456", "zxc"=>"789" }
? aVal[1], aVal[2], aVal[3], hVal["qwe"], hVal["asd"], hVal["zxc"]
p( @aVal[2], @hVal["asd"] )
? aVal[1], aVal[2], aVal[3], hVal["qwe"], hVal["asd"], hVal["zxc"]

proc p( p1, p2 )
p1 := '[1]'
p2 := '[2]'

Compiled by Harbour above code shows:
abc klm xyz 123 456 789
abc [1] xyz 123 [2] 789

In xHarbour only passing array items by reference works but does not work
passing hash items by reference though it does not generate either
compile time or run time errors so the above code can be compiled and
executed but it shows:
abc klm xyz 123 456 789
abc [1] xyz 123 456 789

HMGS-IDE 1.0.7.1 Released on 16th March 2011

CCH : From the HMG Extended Forum

Hi All,

The updated HMGS-IDE 1.0.7.1 binary and sources are published
at the following URL:
http://www.hmgextended.com/files/HMGS-IDE/ide.zip

Whatsnew:
2011-03-16: version 1.0.7.1
*Fixed: problem at creating a new report. Bug was reported by Sudip
*Fixed: problem at deleting the all reports.

You can update this build via clicking 'Update' menuitem in the main
menu 'Help'.

--
Kind Regards,
Grigory Filatov
[MiniGUI Team]

Harbour MiniGUI 1.9 Extended Edition (Build 94) Released on 15th March 2011

CCH: From the HMG Extended Forum

Hi All,

The Harbour MiniGUI 1.9 Extended Edition (Build 94) setup is published at the following URL:

http://hmgextended.com/files/CONTRIB/hmg-1.9-94-setup.zip

There is the following changelog for this build:

2011/03/15: Build 94 (HMG 1.9 Extended Edition) Published.
* Fixed: The 'OnChange' event fired by mouse click in the celled GRID without
changing of the cell. It exists in the official version too.
Contributed by Grigory Filatov
(see demo2.prg in folder \samples\Basic\Grid_7)
* Fixed: The Radiogroup executes 'OnChange' event by mouse click when it's value
is not changed. It exists in the official version too.
Contributed by Grigory Filatov
(see demo1.prg in folder \samples\Basic\RadioGroup)
* Fixed: Minor correction of RadioGroup SetFocus behaviour.
Contributed by Grigory Filatov
* Enhanced: RadioGroup accepts now a zero value. This is usefully when we want
init a radiogroup without default value.
When we assign a value greater or smaller than radiogroup elements amount,
the previous value will be mainted and not display the runtime error.
Based upon a contribution by Eduardo Fernandes
(see demo3.prg in folder \samples\Basic\RadioGroup)
* Enhanced: DATEPICKER control supports a new clause RANGE dRangeMin, dRangeMax.
You can set/get these properties at runtime:
- function syntax:
SetProperty ( Form, DatePick, 'RangeMin', dData )
GetProperty ( Form, DatePick, 'RangeMax' ) --> dData
- pseudo-OOP syntax:
Form.DatePick.RangeMin := dData
Form.DatePick.RangeMax --> dData
You can erase date range at runtime via:
Form.DatePick.RangeMin := 0
Form.DatePick.RangeMax := 0
Requested by Anibal Villalobos Guillen .
Based upon a code by Alfredo Franceschetti .
Contributed by Grigory Filatov
(see demo2.prg in folder \samples\Basic\DatePicker)
* Changed: Minor improvements in the functions InputBox() and InputWindow().
Suggested by Honorio A. S. Almeida .
Contributed by Grigory Filatov
(see demo in folder \samples\Basic\InputBox)
* Changed: The internal function Random() is defined as pseudo-function now.
It is a wrapper for the Harbour function hb_RandomInt().
Contributed by Grigory Filatov
* Changed: The WinAPI constants from h_msgbox.prg are moved to header file i_winuser.ch.
Contributed by Grigory Filatov
(see i_winuser.ch in folder Include\)
* Updated: RichEditBox control:
- Modified: RichEdit Dll v.4.1 unicode support at WinXP SP1 or later.
Based upon a contribution by Janusz Pora .
- Added: unloading RichEdit Dll at program exit.
Contributed by Grigory Filatov .
* Updated: PropGrid library source code (see in folder \Source\PropGrid):
- Fixed: C-code cleaning for warnings with BCC.
Contributed by Grigory Filatov
* Updated: PropSheet library source code (see in folder \Source\PropSheet):
- Fixed: C-code cleaning for warnings with BCC.
Contributed by Grigory Filatov
* Updated: Adaptation FiveWin Class TSBrowse 9.0 in HMG:
- Fixed: Font assigning at inplace editing in btnbox, combo, datepicker and getbox.
- Fixed: Missing Alias qualification in the SetDbf method.
Contributed by Igor Nazarov.
- Changed: Function OrdScope() was used for index based filters.
Contributed by Janusz Pora
* Updated: Harbour Compiler 2.1.0rc2 (SVN 2011-03-11 13:41):
* Updated: most important differences between Harbour and xHarbour
(see xhb-diff.txt in folder \harbour\doc)
Contributed by Grigory Filatov
(look at ReadMe.txt in folder \harbour)
* Updated: HMGS-IDE v.1.0.7. Project Manager and Two-Way Visual Form Designer.
Contributed by Walter Formigoni
(look for what's new at changelog.txt in folder \Ide)
* New: 'Display Structure' sample.
Based upon a contribution by Marcos Antonio Gambeta
(see in folder \samples\Basic\DISPLAY_STRUCTURE)
* New: 'HMG Radiogroup' sample. Borrowed from HMG 4 project.
Adapted by Grigory Filatov
(see demo1.prg in folder \samples\Basic\RadioGroup)
* New: 'TsBrowse Incremental search' sample.
Based upon a contribution by Igor Nazarov
(see in folder \samples\Advanced\Tsb_filter)
* Updated: MsgEdit sample:
- Changed: function hb_GetImageSize() was used instead of XImage.dll.
Based on code contributed by Andi Jahja
(see in folder \samples\Basic\MsgEdit)

This release of MiniGUI is considered stable and ready for production use.

Your comments/feedback are welcome!

--
Best Regards,
Grigory Filatov
[MiniGUI Team]