576b18f214
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@49260 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
283 lines
11 KiB
Plaintext
283 lines
11 KiB
Plaintext
Binary Compatibility and wxWidgets
|
|
==================================
|
|
0. Purpose
|
|
----------
|
|
|
|
This is a broad technote covering all aspects of binary compatibility with
|
|
wxWidgets.
|
|
|
|
1. Releases
|
|
-----------
|
|
|
|
General overview of releases can be found in tn0012.txt, but for
|
|
completeness the wxWidgets release version number is as follows:
|
|
|
|
2.6.2
|
|
|
|
Where
|
|
|
|
2 6 2
|
|
Major Minor Release
|
|
|
|
(I.E. Major.Minor.Release).
|
|
|
|
All versions with EVEN minor version component (e.g. 2.4.x, 2.6.x etc.)
|
|
are expected to be binary compatible (ODD minors are development versions
|
|
and the compatibility constraints don't apply to them). Note that by
|
|
preserving binary compatibility we mean BACKWARDS compatibility only,
|
|
meaning that applications built with old wxWidgets headers should continue
|
|
to work with new wxWidgets (shared/dynamic) libraries without the need to
|
|
rebuild. There is no requirement to preserve compatibility in the other
|
|
direction (i.e. make new headers compatible with old libraries) as this
|
|
would preclude any additions whatsoever to the stable branch. But see
|
|
also section (4).
|
|
|
|
|
|
2. What kind of changes are NOT binary compatible
|
|
-------------------------------------------------
|
|
|
|
If its still up, the KDE guide is a good reference:
|
|
http://developer.kde.org/documentation/other/binarycompatibility.html
|
|
|
|
The changes that are NOT binary compatible:
|
|
- Adding a virtual function
|
|
- Changing the name of a any function or variable
|
|
- Changing the signature of a virtual function (adding a parameter,
|
|
even a default one)
|
|
- Changing the order of the virtual functions in a class
|
|
["switching" them, etc.]
|
|
- Changing access privileges of a function: some compilers (among which MSVC)
|
|
use the function access specifier in its mangled name. Moreover, while
|
|
changing a private function to public should be compatible (as the old
|
|
symbol can't be referenced from outside the library anyhow), changing a
|
|
virtual private function to public is NOT compatible because the old symbol
|
|
is referenced by the virtual tables in the executable code and so an old
|
|
program compiled with MSVC wouldn't start up with a new DLL even if it
|
|
doesn't use the affected symbol at all!
|
|
- Adding a member variable
|
|
- Changing the order of non-static member variables
|
|
|
|
|
|
3. Changes which are compatible
|
|
-------------------------------
|
|
|
|
- Adding a new class
|
|
- Adding a new non-virtual method to an existing class
|
|
- Overriding the implementation of an existing virtual function
|
|
[this is considered to be backwards binary compatible until we find a
|
|
counter example; currently it's known to work with Apple gcc at least]
|
|
- Anything which doesn't result in ABI change at all, e.g. adding new
|
|
macros, constants and, of course, private changes in the implementation
|
|
|
|
|
|
4. wxABI_VERSION and "forward" binary compatibility
|
|
--------------------------------------------------
|
|
|
|
As mentioned we do not support "forward" binary compatibility, that is the
|
|
ability to run applications compiled with new wxWidgets headers on systems
|
|
with old wxWidgets libraries.
|
|
|
|
However, for the developers who want to ensure that their application works
|
|
with some fixed old wxWidgets version and doesn't (inadvertently) require
|
|
features added in later releases, we provide the macro wxABI_VERSION which
|
|
can be defined to restrict the API exported by wxWidgets headers to that of
|
|
a fixed old release.
|
|
|
|
For this to work, all new symbols added to binary compatible releases must
|
|
be #if'ed with wxABI_VERSION.
|
|
|
|
The layout of wxABI_VERSION is as follows:
|
|
|
|
20602
|
|
|
|
where
|
|
|
|
2 06 02
|
|
Major Minor Release
|
|
|
|
I.E. it corresponds to the wxWidgets release in (1).
|
|
|
|
An example of using wxABI_VERSION is as follows for symbols
|
|
only in a 2.6.2 release:
|
|
|
|
#if wxABI_VERSION >= 20602 /* 2.6.2+ only */
|
|
bool Load(const wxURI& location, const wxURI& proxy);
|
|
|
|
wxFileOffset GetDownloadProgress();
|
|
wxFileOffset GetDownloadTotal();
|
|
|
|
bool ShowPlayerControls(
|
|
wxMediaCtrlPlayerControls flags =
|
|
wxMEDIACTRLPLAYERCONTROLS_DEFAULT);
|
|
|
|
//helpers for the wxPython people
|
|
bool LoadURI(const wxString& fileName)
|
|
{ return Load(wxURI(fileName)); }
|
|
bool LoadURIWithProxy(const wxString& fileName, const wxString& proxy)
|
|
{ return Load(wxURI(fileName), wxURI(proxy)); }
|
|
#endif
|
|
|
|
|
|
5. Workarounds for adding virtual functions
|
|
-------------------------------------------
|
|
|
|
Originally the idea for adding virtual functions to binary compatible
|
|
releases was to pad out some empty "reserved" functions and then
|
|
rename those later when someone needed to add a virtual function.
|
|
|
|
However, after there was some actual testing of the idea a lot of
|
|
controversy erupted. Eventually we decided against the idea, and
|
|
instead devised a new method for doing so called wxShadowObject.
|
|
|
|
wxShadowObject is a class derived from wxObject that provides a means
|
|
of adding functions and/or member variables to a class internally
|
|
to wxWidgets. It does so by storing these in a hash map inside of
|
|
it, looking it up when the function etc. is called. wxShadowObject
|
|
is generally stored inside a reserved member variable.
|
|
|
|
wxShadowObject resides in include/wx/clntdata.h.
|
|
|
|
To use wxShadowObject, you first call AddMethod or AddField with
|
|
the first parameter being the name of the field and/or method
|
|
you want, and the second parameter being the value of the
|
|
field and/or method.
|
|
|
|
In the case of fields this is a void*, and in the case of method
|
|
is a wxShadowObjectMethod which is a typedef:
|
|
typedef int (*wxShadowObjectMethod)(void*, void*);
|
|
|
|
After you add a field, you can set it via SetField with the same
|
|
parameters as AddField, the second parameter being the value to set
|
|
the field to. You can get the field after you call AddField
|
|
via GetField, with the parameters as the other two field functions,
|
|
only in the case the second parameter is the fallback
|
|
value for the field in the case of it not being found in the
|
|
hash map.
|
|
|
|
You can call a method after you add it via InvokeMethod, which
|
|
returns a bool indicating whether or not the method was found
|
|
in the hash map, and has 4 parameters. The first parameter is
|
|
the name of the method you wish to call, the second is the first
|
|
parameter passed to the wxShadowObjectMethod, the third is the
|
|
second parameter passed to that wxShadowObjectMethod, and the
|
|
fourth is the return value of the wxShadowObjectMethod.
|
|
|
|
6. version-script.in
|
|
--------------------
|
|
|
|
For ld/libtool we use sun-style version scripts. Basically
|
|
anything which fits the conditions of being #if'ed via wxABI_VERSION
|
|
needs to go here also.
|
|
|
|
See 'info ld scripts version' on a GNU system, it's online here:
|
|
http://www.gnu.org/software/binutils/manual/ld-2.9.1/html_node/ld_25.html
|
|
|
|
Or see chapter 5 of the 'Linker and Libraries Guide' for Solaris, available
|
|
online here:
|
|
http://docsun.cites.uiuc.edu/sun_docs/C/solaris_9/SUNWdev/LLM/p1.html
|
|
|
|
The file has the layout as follows:
|
|
|
|
@WX_VERSION_TAG@.X
|
|
|
|
Where X is the current Release as mentioned earlier, i.e. 2. This
|
|
is following by an opening bracket "{", followed by "global:",
|
|
followed by patterns matching added symbols, then followed by "}", and then
|
|
the file is either followed by earlier Releases or ended by
|
|
a @WX_VERSION_TAG@ block without the period or Release.
|
|
|
|
The patterns used to specify added symbols are globbing patters and can
|
|
contain wildcards such as '*'.
|
|
|
|
For example for a new class member such as:
|
|
wxFont wxGenericListCtrl::GetItemFont( long item ) const;
|
|
|
|
the mangled symbol might be:
|
|
_ZNK17wxGenericListCtrl11GetItemFontEl
|
|
|
|
so a line like this could be added to version-script.in:
|
|
*wxGenericListCtrl*GetItemFont*;
|
|
|
|
Allow for the fact that the name mangling is going to vary from compiler to
|
|
complier.
|
|
|
|
When adding a class you can match all the symbols it adds with a single
|
|
pattern, so long as that pattern is not likely to also match other symbols.
|
|
For example for wxLogBuffer a line like this:
|
|
*wxLogBuffer*;
|
|
|
|
|
|
7. Checking the version information in libraries and programs
|
|
-------------------------------------------------------------
|
|
|
|
On Sun there is a tool for this, see pvs(1). On GNU you can use objdump, below
|
|
are some examples.
|
|
|
|
To see what versions of each library a program (or library) depends on:
|
|
|
|
$ objdump -p widgets | sed -ne '/Version References/,/^$/p'
|
|
Version References:
|
|
required from libgcc_s.so.1:
|
|
0x0b792650 0x00 10 GCC_3.0
|
|
required from libwx_based-2.6.so.0:
|
|
0x0cca2546 0x00 07 WXD_2.6
|
|
required from libstdc++.so.6:
|
|
0x056bafd3 0x00 09 CXXABI_1.3
|
|
0x08922974 0x00 06 GLIBCXX_3.4
|
|
required from libwx_gtk2d_core-2.6.so.0:
|
|
0x0a2545d2 0x00 08 WXD_2.6.2
|
|
0x0cca2546 0x00 05 WXD_2.6
|
|
required from libc.so.6:
|
|
0x09691a75 0x00 04 GLIBC_2.2.5
|
|
|
|
To see what WXD_2.6.2 symbols a program uses:
|
|
|
|
$ objdump -T widgets | grep 'WXD_2\.6\.2'
|
|
0000000000000000 g DO *ABS* 0000000000000000 WXD_2.6.2 WXD_2.6.2
|
|
00000000004126d8 DF *UND* 0000000000000177 WXD_2.6.2 _ZN19wxTopLevelWindowGTK20RequestUserAttentionEi
|
|
|
|
To see what WXD_2.6.2 symbols a library defines:
|
|
|
|
$ objdump -T libwx_based-2.6.so | grep 'WXD_2\.6\.2' | grep -v 'UND\|ABS'
|
|
0000000000259a10 w DO .data 0000000000000018 WXD_2.6.2 _ZTI19wxMessageOutputBest
|
|
00000000002599e0 w DO .data 0000000000000028 WXD_2.6.2 _ZTV19wxMessageOutputBest
|
|
000000000010a98e w DF .text 000000000000003e WXD_2.6.2 _ZN19wxMessageOutputBestD0Ev
|
|
0000000000114efb w DO .rodata 000000000000000e WXD_2.6.2 _ZTS11wxLogBuffer
|
|
0000000000255590 w DO .data 0000000000000018 WXD_2.6.2 _ZTI11wxLogBuffer
|
|
000000000011b550 w DO .rodata 0000000000000016 WXD_2.6.2 _ZTS19wxMessageOutputBest
|
|
00000000000bfcc8 g DF .text 00000000000000dd WXD_2.6.2 _ZN11wxLogBuffer5DoLogEmPKcl
|
|
000000000010a3a6 g DF .text 0000000000000153 WXD_2.6.2 _ZN19wxMessageOutputBest6PrintfEPKcz
|
|
00000000000c0b22 w DF .text 000000000000004b WXD_2.6.2 _ZN11wxLogBufferD0Ev
|
|
00000000000bfc3e g DF .text 0000000000000089 WXD_2.6.2 _ZN11wxLogBuffer5FlushEv
|
|
00000000000c0ad6 w DF .text 000000000000004b WXD_2.6.2 _ZN11wxLogBufferD1Ev
|
|
00000000000b1130 w DF .text 0000000000000036 WXD_2.6.2 _ZN11wxLogBufferC1Ev
|
|
00000000000c095c w DF .text 0000000000000029 WXD_2.6.2 _ZN19wxMessageOutputBestC1Ev
|
|
00000000000c08e8 w DF .text 000000000000003e WXD_2.6.2 _ZN19wxMessageOutputBestD1Ev
|
|
00000000002554c0 w DO .data 0000000000000038 WXD_2.6.2 _ZTV11wxLogBuffer
|
|
00000000000bfda6 g DF .text 0000000000000036 WXD_2.6.2 _ZN11wxLogBuffer11DoLogStringEPKcl
|
|
00000000000abe10 g DF .text 0000000000000088 WXD_2.6.2 _ZN14wxZipFSHandler7CleanupEv
|
|
|
|
|
|
8. Testing binary compatibility between releases
|
|
------------------------------------------------
|
|
|
|
An easy way of testing binary compatibility is just to build wxWidgets
|
|
in dll/dynamic library mode and then switch out the current library
|
|
in question with an earlier stable version of the library, then running
|
|
the application in question again. If it runs OK then there is usually
|
|
binary compatibility between those releases.
|
|
|
|
You can also break into your debugger or whatever program you want
|
|
to use and check the memory layout of the class. If it is the same
|
|
then it is binary compatible.
|
|
|
|
Also remember to look at http://www.wxwidgets.org/bincompat.html page which
|
|
summarizes the results of testing of all the samples built against old
|
|
libraries headers with the new library binaries under Unix.
|
|
|
|
|
|
=== EOF ===
|
|
|
|
Author: RN
|
|
Version: $Id$
|