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3 <HEAD>
4 <TITLE>wxWidgets 2 for Windows FAQ</TITLE>
5 </HEAD>
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7 <BODY BGCOLOR=#FFFFFF TEXT=#000000 VLINK="#00376A" LINK="#00529C" ALINK="#313063">
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9 <font face="Arial, Lucida Sans, Helvetica">
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11 <table width=100% border=0 cellpadding=3 cellspacing=0>
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13 <td bgcolor="#004080" align=left height=24 background="images/bluetitlegradient.gif">
14 <font size=+1 face="Arial, Lucida Sans, Helvetica" color="#FFFFFF">
15 <b>wxWidgets 2 for Windows FAQ</b>
16 </font>
17 </td>
18 </tr>
19 </table>
20
21 <P>
22
23 See also <a href="faq.htm">top-level FAQ page</a>.
24 <hr>
25 <h3>List of questions in this category</h3>
26 <ul>
27 <li><a href="#platforms">Which Windows platforms are supported?</a></li>
28 <li><a href="#wince">What about Windows CE?</a></li>
29 <li><a href="#winxp">What do I need to do for Windows XP?</a></li>
30 <li><a href="#compilers">What compilers are supported?</a></li>
31 <li><a href="#bestcompiler">Which is the best compiler to use with wxWidgets 2?</a></li>
32 <li><a href="#unicode">Is Unicode supported?</a></li>
33 <li><a href="#doublebyte">Does wxWidgets support double byte fonts (Chinese/Japanese/Korean etc.)?</a></li>
34 <li><a href="#dll">Can you compile wxWidgets 2 as a DLL?</a></li>
35 <li><a href="#exesize">How can I reduce executable size?</a></li>
36 <li><a href="#mfc">Is wxWidgets compatible with MFC?</a></li>
37 <li><a href="#setuph">Why do I get errors about setup.h not being found?</a></li>
38 <li><a href="#asuffix">Why do I get errors about FooBarA when I only use FooBar in my program?</a></li>
39 <li><a href="#newerrors">Why my code fails to compile with strange errors about new operator?</a></li>
40 <li><a href="#mfcport">How do I port MFC applications to wxWidgets?</a></li>
41 <li><a href="#crash">Why do I sometimes get bizarre crash problems using VC++ 5/6?</a></li>
42 <li><a href="#makefiles">How are the wxWidgets makefiles edited under Windows?</a></li>
43 <li><a href="#vcdebug">How do you use VC++&#39;s memory leak checking instead of that in wxWidgets?</a></li>
44 <li><a href="#shortcutproblem">Why are menu hotkeys or shortcuts not working in my application?</a></li>
45 <li><a href="#regconfig">Why can I not write to the HKLM part of the registry with wxRegConfig?</a></li>
46 <li><a href="#access">Is MS Active Accessibility supported?</a></li>
47 <li><a href="#dspfmt">Why does Visual C++ complain about corrupted project files??</a></li>
48 <li><a href="#crtmismatch">Visual C++ gives errors about multiply defined symbols, what can I do?</a></li>
49 </ul>
50 <hr>
51
52 <h3><a name="platforms">Which Windows platforms are supported?</a></h3>
53
54 wxWidgets 2 can be used to develop and deliver applications on Windows 3.1, Win32s,
55 Windows 95, Windows 98, Windows NT, Windows 2000, and Windows XP. A Windows CE
56 version is being looked into (see below).<P>
57
58 wxWidgets 2 is designed to make use of WIN32 features and controls. However, unlike Microsoft,
59 we have not forgotten users of 16-bit Windows. Most features
60 work under Windows 3.1, including wxTreeCtrl and wxListCtrl using the generic implementation.
61 However, don&#39;t expect very Windows-95-specific classes to work, such as wxTaskBarIcon. The wxRegConfig
62 class doesn&#39;t work either because the Windows 3.1 registry is very simplistic. Check out the 16-bit
63 makefiles to see what other files have been left out.
64 <P>
65 16-bit compilation is supported under Visual C++ 1.5, and Borland BC++ 4 to 5.
66 <P>
67
68 wxWidgets 2 for Windows will also compile on Unix with gcc using Wine from <a href="http://www.winehq.org" target=_top>WineHQ</a>.
69 The resulting executables are Unix binaries that work with the Wine Windows API emulator.<P>
70
71 You can also compile wxWidgets 2 for Windows on Unix with Cygwin or Mingw32, resulting
72 in executables that will run on Windows. So in theory you could write your applications
73 using wxGTK or wxMotif, then check/debug your wxWidgets for Windows
74 programs with Wine, and finally produce an ix86 Windows executable using Cygwin/Mingw32,
75 without ever needing a copy of Microsoft Windows. See the Technical Note on the Web site detailing cross-compilation.<P>
76
77 <h3><a name="wince">What about Windows CE?</a></h3>
78
79 This port is largely complete. For further information, see the <a href="http://www.wxwidgets.org/embedded.htm#wxwince">wxEmbedded</a> page.<P>
80
81 <h3><a name="winxp">What do I need to do for Windows XP?</a></h3>
82
83 In the same directory as you have your executable (e.g. foo.exe) you
84 put a file called foo.exe.manifest in which you have something like
85 the following:
86
87 <pre>
88 &lt;?xml version="1.0" encoding="UTF-8" standalone="yes"?&gt;
89 &lt;assembly
90 xmlns="urn:schemas-microsoft-com:asm.v1"
91 manifestVersion="1.0"&gt;
92 &lt;assemblyIdentity
93 processorArchitecture="x86"
94 version="5.1.0.0"
95 type="win32"
96 name="foo.exe"/&gt;
97 &lt;description&gt;Foo program&lt;/description&gt;
98 &lt;dependency&gt;
99 &lt;dependentAssembly&gt;
100 &lt;assemblyIdentity
101 type="win32"
102 name="Microsoft.Windows.Common-Controls"
103 version="6.0.0.0"
104 publicKeyToken="6595b64144ccf1df"
105 language="*"
106 processorArchitecture="x86"/&gt;
107 &lt;/dependentAssembly&gt;
108 &lt;/dependency&gt;
109 &lt;/assembly&gt;
110 </pre>
111
112 If you want to add it to your application permanently,
113 you can also include it in your .rc file using this
114 line:<P>
115
116 <PRE>
117 1 24 "winxp.manifest"
118 </PRE>
119
120 In wxWidgets 2.5, this will be in the wx/msw/wx.rc and
121 so will happen automatically so long as you include wx.rc
122 in your own .rc file.<P>
123
124 For an explanation of this syntax, please see
125 <a href="http://delphi.about.com/library/bluc/text/uc111601a.htm" target=_new>this
126 article</a>.
127 <P>
128
129 <h3><a name="compilers">What compilers are supported?</a></h3>
130
131 Please see the wxWidgets 2 for Windows install.txt file for up-to-date information, but
132 currently the following are known to work:<P>
133
134 <ul>
135 <li>Visual C++ 1.5, 4.0, 5.0, 6.0, 7.0, 7.1
136 <li>Borland C++ 4.5, 5.0, 5.5
137 <li>Borland C++Builder 1.0, 3.0, X
138 <li>Watcom C++ 10.6 (Win32), OpenWatcom 1.0
139 <li>Cygwin (using configure)
140 <li>Mingw32
141 <li>MetroWerks CodeWarrior (many versions)
142 <li>Digital Mars 8.34+
143 </ul>
144 <P>
145
146
147 <h3><a name="bestcompiler">Which is the best compiler to use with wxWidgets 2?</a></h3>
148
149 It&#39;s partly a matter of taste, but I (JACS) prefer Visual C++ since the debugger is very
150 good, it&#39;s very stable, the documentation is extensive, and it generates small executables.
151 Since project files are plain text, it&#39;s easy for me to generate appropriate project files
152 for wxWidgets samples.<P>
153
154 Borland C++ is fine - and very fast - but it&#39;s hard (impossible?) to use the debugger without using project files, and
155 the debugger is nowhere near up to VC++&#39;s quality. The IDE isn&#39;t great.<P>
156
157 C++Builder&#39;s power isn&#39;t really used with wxWidgets since it needs integration with its
158 own class library (VCL). For wxWidgets, I&#39;ve only used it with makefiles, in which case
159 it&#39;s almost identical to BC++ 5.0 (the same makefiles can be used).<P>
160
161 You can&#39;t beat Cygwin&#39;s price (free), and you can debug adequately using gdb. However, it&#39;s
162 quite slow to compile since it does not use precompiled headers.<P>
163
164 CodeWarrior is cross-platform - you can debug and generate Windows executables from a Mac, but not
165 the other way around I think - but the IDE is, to my mind, a bit primitive.<P>
166
167 Watcom C++ is a little slow and the debugger is not really up to today&#39;s standards.<P>
168
169 Among the free compilers the best choice seem to be Borland C++ command line
170 tools and mingw32 (port of gcc to Win32). Both of them are supported by
171 wxWidgets.
172
173 <h3><a name="unicode">Is Unicode supported?</a></h3>
174
175 Yes, Unicode is fully supported under Windows NT/2000 and there is limited
176 support for it under Windows 9x using <a
177 href="http://www.microsoft.com/globaldev/handson/dev/mslu_announce.mspx">MSLU</a>.
178 <p>
179
180 <h3><a name="doublebyte">Does wxWidgets support double byte fonts (Chinese/Japanese/Korean etc.)?</a></h3>
181
182 For Japanese under Win2000, it seems that wxWidgets has no problems to work
183 with double byte char sets (meaning DBCS, not Unicode). First you have to
184 install Japanese support on your Win2K system and choose for ANSI translation
185 <tt>HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Nls\CodePage=932</tt>
186 (default is 1252 for Western). Then you can see all the Japanese letters in
187 wxWidgets applications.
188 <p>
189
190 <h3><a name="dll">Can you compile wxWidgets 2 as a DLL?</a></h3>
191
192 Yes (using the Visual C++ or Borland C++ makefile), but be aware that distributing DLLs is a thorny issue
193 and you may be better off compiling statically-linked applications, unless you&#39;re
194 delivering a suite of separate programs, or you&#39;re compiling a lot of wxWidgets applications
195 and have limited hard disk space.<P>
196
197 With a DLL approach, and with different versions and configurations of wxWidgets
198 needing to be catered for, the end user may end up with a host of large DLLs in his or her Windows system directory,
199 negating the point of using DLLs. Of course, this is not a problem just associated with
200 wxWidgets!
201 <P>
202
203 <h3><a name="exesize">How can I reduce executable size?</a></h3>
204
205 You can compile wxWidgets as a DLL (see above, VC++/BC++ only at present). You should also
206 compile your programs for release using non-debugging and space-optimisation options, but
207 take with VC++ 5/6 space optimisation: it can sometimes cause problems.<P>
208
209 If you want to distribute really small executables, you can
210 use <a href="http://www.un4seen.com/petite/" target=_top>Petite</a>
211 by Ian Luck. This nifty utility compresses Windows executables by around 50%, so your 500KB executable
212 will shrink to a mere 250KB. With this sort of size, there is reduced incentive to
213 use DLLs. Another good compression tool (probably better than Petite) is <a href="http://upx.sourceforge.net/" target=_top>UPX</a>.
214 <P>
215
216 Please do not be surprised if MinGW produces a statically-linked minimal executable of 1 MB. Firstly, gcc
217 produces larger executables than some compilers. Secondly, this figure will
218 include most of the overhead of wxWidgets, so as your application becomes more
219 complex, the overhead becomes proportionally less significant. And thirdly, trading executable compactness
220 for the enormous increase in productivity you get with wxWidgets is almost always well worth it.<P>
221
222 If you have a really large executable compiled with MinGW (for example 20MB) then
223 you need to configure wxWidgets to compile without debugging information: see
224 docs/msw/install.txt for details. You may find that using configure instead
225 of makefile.g95 is easier, particularly since you can maintain debug and
226 release versions of the library simultaneously, in different directories.
227 Also, run 'strip' after linking to remove all traces of debug info.
228 <P>
229
230 <H3><a name="mfc">Is wxWidgets compatible with MFC?</a></H3>
231
232 There is a sample which demonstrates MFC and wxWidgets code co-existing in the same
233 application. However, don&#39;t expect to be able to enable wxWidgets windows with OLE-2
234 functionality using MFC.<P>
235
236 <H3><a name="setuph">Why do I get errors about setup.h not being found?</a></H3>
237
238 When you build the wxWidgets library, setup.h is copied
239 from include/wx/msw/setup.h to e.g. lib/mswd/wx/setup.h (the path
240 depends on the configuration you&#39;re building). So you need to add
241 this include path if building using the static Debug library:<P>
242
243 lib/mswd<P>
244
245 or if building the static Release library, lib/msw.<P>
246
247 See also the <a href="http://wiki.wxwidgets.org/wiki.pl?Table_Of_Contents">wxWiki Contents</a>
248 for more information.<P>
249
250
251 <H3><a name="asuffix">Why do I get errors about FooBarA when I only use FooBar in my program?</H3>
252
253 If you get errors like
254 <p>
255 <center>
256 <tt>no matching function for call to &#39;wxDC::DrawTextA(const char[5], int,
257 int)&#39;</tt>
258 </center>
259 <p>
260 or similar ones for the other functions, i.e. the compiler error messages
261 mention the function with the <tt>&#39;A&#39;</tt> suffix while you didn&#39;t
262 use it in your code, the explanation is that you had included
263 <tt>&#60;windows.h&#062;</tt> header which redefines many symbols to have such
264 suffix (or <tt>&#39;W&#39;</tt> in the Unicode builds).
265
266 <p>
267 The fix is to either not include <tt>&#60;windows.h&#62;</tt> at all or include
268 <tt>"wx/msw/winundef.h"</tt> immediately after it.
269
270 <H3><a name="newerrors">Why my code fails to compile with strange errors about new operator?</a></H3>
271
272 The most common cause of this problem is the memory debugging settings in
273 <tt>wx/msw/setup.h</tt>. You have several choices:
274
275 <ul>
276 <li> Either disable overloading the global operator new completely by
277 setting <tt>wxUSE_GLOBAL_MEMORY_OPERATORS</tt> and
278 <tt>wxUSE_DEBUG_NEW_ALWAYS</tt> to 0 in this file
279 <li> Or leave them on but do <tt>#undef new</tt> after including any
280 wxWidgets headers, like this the memory debugging will be still on
281 for wxWidgets sources but off for your own code
282 </ul>
283
284 Notice that IMHO the first solution is preferable for VC++ users who can use
285 the <a href="#vcdebug">VC++ CRT memory debugging features</a> instead.
286
287 <H3><a name="mfcport">How do I port MFC applications to wxWidgets?</a></H3>
288
289 Set up your interface from scratch using wxWidgets (especially <a href="http://www.robeling.de" target=_top>wxDesigner</a>
290 or <a href="http://www.anthemion.co.uk/dialogblocks/" target=_new>DialogBlocks</a> --
291 it&#39;ll save you a <i>lot</i> of time) and when you have a shell prepared, you can start
292 &#39;pouring in&#39; code from the MFC app, with appropriate
293 modifications. This is the approach I have used, and I found
294 it very satisfactory. A two-step process then - reproduce the bare
295 interface first, then wire it up afterwards. That way you deal
296 with each area of complexity separately. Don&#39;t try to think MFC
297 and wxWidgets simultaneously from the beginning - it is easier to
298 reproduce the initial UI by looking at the behaviour of the MFC
299 app, not its code.
300
301 <H3><a name="crash">Why do I sometimes get bizarre crash problems using VC++ 5/6?</a></H3>
302
303 Some crash problems can be due to inconsistent compiler
304 options (and of course this isn&#39;t limited to wxWidgets).
305 If strange/weird/impossible things start to happen please
306 check (dumping IDE project file as makefile and doing text comparison
307 if necessary) that the project settings, especially the list of defined
308 symbols, struct packing, etc. are exactly the same for all items in
309 the project. After this, delete everything (including PCH) and recompile.<P>
310
311 VC++ 5&#39;s optimization code seems to be broken and can
312 cause problems: this can be seen when deleting an object Dialog
313 Editor, in Release mode with optimizations on. If in doubt,
314 switch off optimisations, although this will result in much
315 larger executables. It seems possible that the library can be created with
316 strong optimization, so long as the application is not strongly
317 optimized. For example, in wxWidgets project, set to &#39;Minimum
318 Size&#39;. In Dialog Editor project, set to &#39;Customize: Favor Small
319 Code&#39; (and no others). This will then work.<P>
320
321 <H3><a name="makefiles">How are the wxWidgets makefiles edited under Windows?</a></H3>
322
323 As of wxWidgets 2.1, there is a new system written by Vadim Zeitlin, that
324 generates the makefiles from templates using tmake.<P>
325
326 Here are Vadim&#39;s notes:<P>
327
328 <blockquote>
329 To use these new makefiles, you don&#39;t need anything (but see below).
330 However, you should NOT modify them because these files will be
331 rewritten when I regenerate them using tmake the next time. So, if
332 you find a problem with any of these makefiles (say, makefile.b32)
333 you&#39;ll need to modify the corresponding template (b32.t in this
334 example) and regenerate the makefile using tmake.<P>
335
336 tmake can be found at
337 <a href="http://www.troll.no/freebies/tmake.html" target=_new>www.troll.no/freebies/tmake.html</a>.
338 It&#39;s a Perl5 program and so it needs Perl (doh). There is a binary for
339 Windows (available from the same page), but I haven&#39;t used it, so
340 I don&#39;t know if it works as flawlessly as "perl tmake" does (note
341 for people knowing Perl: don&#39;t try to run tmake with -w, it won&#39;t
342 do you any good). Using it extremely simple: to regenerate makefile.b32
343 just go to distrib/msw/tmake and type<P>
344
345 <pre>tmake -t b32 wxwin.pro -o ../../src/msw/makefile.b32</pre><P>
346
347 The makefiles are untested - I don&#39;t have any of Borland, Watcom or
348 Symantec and I don&#39;t have enough diskspace to recompile even with
349 VC6 using makefiles. The new makefiles are as close as possible to the
350 old ones, but not closer: in fact, there has been many strange things
351 (should I say bugs?) in some of makefiles, some files were not compiled
352 without any reason etc. Please test them and notify me about any problems.
353 Better yet, modify the template files to generate the correct makefiles
354 and check them in.<P>
355
356 The templates are described in tmake ref manual (1-2 pages of text)
357 and are quite simple. They do contain some Perl code, but my Perl is
358 primitive (very C like) so it should be possible for anybody to make
359 trivial modifications to it (I hope that only trivial modifications
360 will be needed). I&#39;ve tagged the ol makefiles as MAKEFILES_WITHOUT_TMAKE
361 in the cvs, so you can always retrieve them and compare the new ones,
362 this will make it easier to solve the problems you might have.<P>
363
364 Another important file is filelist.txt: it contains the list of all
365 files to be compiled. Some of them are only compiled in 16/32 bit mode.
366 Some other are only compiled with some compilers (others can&#39;t compile
367 them) - all this info is contained in this file.<P>
368
369 So now adding a new file to wxWidgets is as easy as modifying filelist.txt
370 (and Makefile.ams for Unix ports) and regenerating the makefiles - no
371 need to modify all files manually any more.<P>
372
373 Finally, there is also a file vc6.t which I use myself: this one
374 generates a project file for VC++ 6.0 (I didn&#39;t create vc5.t because
375 I don&#39;t need it and can&#39;t test it, but it should be trivial to create
376 one from vc6.t - probably the only things to change would be the
377 version number in the very beginning and the /Z option - VC5 doesn&#39;t
378 support edit-and=continue). This is not an officially supported way
379 of building wxWidgets (that is, nobody guarantees that it will work),
380 but it has been very useful to me and I hope it will be also for
381 others. To generate wxWidgets.dsp run<P>
382
383 <pre>tmake -t vc6 wxwin.pro -o ../../wxWidgets.dsp</pre><P>
384
385 Then just include this project in any workspace or open it from VC IDE
386 and it will create a new workspace for you.<P>
387
388 If all goes well, I&#39;m planning to create a template file for Makefile.ams
389 under src/gtk and src/motif and also replace all makefiles in the samples
390 subdirectories with the project files from which all the others will be
391 generated. At least it will divide the number of files in samples
392 directory by 10 (and the number of files to be maintained too).
393 </blockquote>
394
395 <P>
396
397 <H3><a name="vcdebug">How do you use VC++&#39;s memory leak checking instead of that in wxWidgets?</a></H3>
398
399 Vadim Zeitlin:
400
401 <pre>
402 On the VC++ level, it&#39;s just the matter of calling _CrtSetDbgFlag() in the very
403 beginning of the program. In wxWidgets, this is done automatically when
404 compiling with VC++ in debug mode unless wxUSE_GLOBAL_MEMORY_OPERATORS or
405 __NO_VC_CRTDBG__ are defined - this check is done in wx/msw/msvcrt.h which
406 is included from app.cpp which then calls wxCrtSetDbgFlag() without any
407 ifdefs.
408
409 This works quite well: at the end of the program, all leaked blocks with their
410 malloc count are shown. This number (malloc count) can be used to determine
411 where exactly the object was allocated: for this it&#39;s enough to set the variable
412 _crtBreakAlloc (look in VC98\crt\srs\dbgheap.c line 326) to this number and
413 a breakpoint will be triggered when the block with this number is allocated.
414
415 For simple situations it works like a charm. For something more complicated
416 like reading uninitialized memory a specialized tool is probably better...
417
418 Regards,
419 VZ
420 </pre>
421
422 <P>
423
424 <H3><a name="shortcutproblem">Why are menu hotkeys or shortcuts not working in my application?</a></H3>
425
426 This can happen if you have a child window intercepting EVT_CHAR events and swallowing
427 all keyboard input. You should ensure that event.Skip() is called for all input that
428 isn&#39;used by the event handler.<P>
429
430 It can also happen if you append the submenu to the parent
431 menu {\it before} you have added your menu items. Do the append {\it after} adding
432 your items, or accelerators may not be registered properly.<P>
433
434 <H3><a name="#regconfig">Why can I not write to the HKLM part of the registry with wxRegConfig?</a></H3>
435
436 Currently this is not possible because the wxConfig family of classes is
437 supposed to deal with per-user application configuration data, and HKLM is
438 only supposed to be writeable by a user with Administrator privileges. In theory,
439 only installers should write to HKLM. This is still a point debated by the
440 wxWidgets developers. There are at least two ways to work around it if you really
441 need to write to HKLM.<P>
442
443 First, you can use wxRegKey directly, for example:
444
445 <pre>
446 wxRegKey regKey;
447
448 wxString idName(wxT("HKEY_LOCAL_MACHINE\\SOFTWARE\\My Company\\My Product\\Stuff\\"));
449 idName += packid;
450
451 regKey.SetName(idName);
452
453 {
454 wxLogNull dummy;
455 if (!regKey.Create())
456 {
457 idName = wxT("HKEY_CURRENT_USER\\SOFTWARE\\My Company\\My Product\\Stuff\\");
458 idName += packid;
459 regKey.SetName(idName);
460 if (!regKey.Create())
461 return FALSE;
462 }
463 }
464
465 if (!regKey.SetValue(wxT("THING"), (long) thing)) err += 1;
466
467 regKey.Close();
468
469 </pre>
470
471 Or, you can employ this trick suggested by Istvan Kovacs:
472
473 <pre>
474 class myGlobalConfig : public wxConfig
475 {
476 myGlobalConfig() :
477 wxConfig ("myApp", "myCompany", "", "", wxCONFIG_USE_GLOBAL_FILE)
478 {};
479 bool Write(const wxString& key, const wxString& value);
480 }
481
482 bool myGlobalConfig::Write (const wxString& key, const wxString& value)
483 {
484 wxString path = wxString ("SOFTWARE\\myCompany\\myApp\\") + wxPathOnly(key);
485 wxString new_path = path.Replace ("/", "\\", true);
486 wxString new_key = wxFileNameFromPath (key);
487 LocalKey().SetName (wxRegKey::HKLM, path);
488 return wxConfig::Write (new_key, value);
489 }
490 </pre>
491
492 <H3><a name="#access">Is MS Active Accessibility supported?</a></H3>
493
494 This is being worked on. Please see <a href="http://www.wxwidgets.org/access.htm">this page</a>
495 for the current status.
496
497 <P>
498
499
500 <h3><a name="#dspfmt">Why does Visual C++ complain about corrupted project files??</a></h3>
501
502 If you have downloaded the wxWidgets sources from the cvs using a Unix cvs
503 client or downloaded a daily snapshot in <tt>.tar.gz</tt> format, it is likely
504 that the project files have Unix line endings (LF) instead of the DOS ones (CR
505 LF). However all versions of Visual C++ up to and including 7.1 can only open
506 the files with the DOS line endings, so you must transform the files to this
507 format using any of the thousands ways to do it.
508 <p>
509 Of course, another possibility is to always use only the Windows cvs client
510 and to avoid this problem completely.
511 <p>
512
513 <h3><a name="#crtmismatch">Visual C++ gives errors about multiply defined symbols, what can I do?</a></h3>
514
515 If you get errors like this
516
517 <pre>
518 MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _xxxxxx already defined in LIBCD.lib(yyyyy.obj)
519 </pre>
520
521 when linking your project, this means that you used different versions of CRT
522 (C Run-Time) library for wxWindows (or possibly another library) and the main
523 project. Visual C++ provides static or dynamic and multithread safe or not
524 versions of CRT for each of debug and release builds, for a total of 8
525 libraries. You can choose among them by going to the "Code generation"
526 page/subitem of the "C++" tab/item in the project proprieties dialog in VC6/7.
527 <p>
528 To avoid problems, you <strong>must</strong> use the same one for all
529 components of your project. wxWindows uses multithread safe DLL version of the
530 CRT which is a good choice but may be problematic when distributing your
531 applications if you don&#39;t include the CRT DLL in your installation -- in this
532 case you may decide to switch to using a static CRT version. If you build with
533 <tt>wxUSE_THREADS == 0</tt> you may also use the non MT-safe version as it is
534 slightly smaller and faster.
535 <p>
536 But the most important thing is to use the <strong>same</strong> CRT setting for
537 all components of your project.
538
539 </font>
540
541 </BODY>
542
543 </HTML>