263 lines
10 KiB
Plaintext
263 lines
10 KiB
Plaintext
<chapter id="portability-issues">
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<title id="portability-issues.title">Portability issues</title>
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<sect1 id="unicode">
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<title id="unicode.title">Unicode</title>
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<para>
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The <literal>wchar_t</literal> type has different standard
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sizes in Unix (4 bytes) and Windows (2 bytes). You need a
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recent gcc version (2.9.7 or later) that supports the
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<parameter>-fshort-wchar</parameter> option to set the
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size of <literal>wchar_t</literal> to the one expected
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by Windows applications.
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</para>
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<para>
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If you are using Unicode and you want to be able to use
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standard library calls (e.g. <function>wcslen</function>,
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<function>wsprintf</function>), then you must use
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the msvcrt runtime library instead of glibc. The functions in
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glibc will not work correctly with 16 bit strings.
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</para>
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</sect1>
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<sect1 id="C-library">
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<title id="C-library.title">C library</title>
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<para>
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There are 2 choices available to you regarding which C library
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to use: the native glibc C library or the msvcrt C library.
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</para>
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<para>
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Note that under Wine, the crtdll library is implemented using
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msvcrt, so there is no benefit in trying to use it.
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</para>
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<para>
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Using glibc in general has the lowest overhead, but this is
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really only important for file I/O, as many of the functions
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in msvcrt are simply resolved to glibc.
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</para>
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<para>
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To use glibc, you don't need to make changes to your
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application; it should work straight away. There are a few
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situations in which using glibc is not possible:
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</para>
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<orderedlist>
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<listitem>
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<para>
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Your application uses Win32 and C library unicode
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functions.
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</para>
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</listitem>
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<listitem>
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<para>
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Your application uses MS specific calls like
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<function>beginthread()</function>,
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<function>loadlibrary()</function>, etc.
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</para>
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</listitem>
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<listitem>
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<para>
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You rely on the precise semantics of the calls, for
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example, returning <literal>-1</literal> rather than
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non-zero. More likely, your application will rely on calls
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like <function>fopen()</function> taking a Windows path
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rather than a Unix one.
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</para>
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</listitem>
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</orderedlist>
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<para>
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In these cases you should use msvcrt to provide your C runtime
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calls.
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</para>
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<programlisting>import msvcrt.dll</programlisting>
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<para>
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to your applications <filename>.spec</filename> file. This
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will cause <command>winebuild</command> to resolve your c
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library calls to <filename>msvcrt.dll</filename>. Many simple
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calls which behave the same have been specified as
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non-importable from msvcrt; in these cases
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<command>winebuild</command> will not resolve them and the
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standard linker <command>ld</command> will link to the glibc
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version instead.
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</para>
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<para>
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In order to avoid warnings in C (and potential errors in C++)
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from not having prototypes, you may need to use a set of MS
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compatible header files. These are scheduled for inclusion
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into Wine but at the time of writing are not available. Until
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they are, you can try prototyping the functions you need, or
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just live with the warnings.
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</para>
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<para>
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If you have a set of include files (or when they are available
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in Wine), you need to use the <parameter>-isystem
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"include_path"</parameter> flag to gcc to tell it to use your
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headers in preference to the local system headers.
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</para>
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<para>
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To use option 3, add the names of any symbols that you don't
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want to use from msvcrt into your applications
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<filename>.spec</filename> file. For example, if you wanted
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the MS specific functions, but not file I/O, you could have a
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list like:
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</para>
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<programlisting>@ignore = ( fopen fclose fwrite fread fputs fgets )</programlisting>
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<para>
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Obviously, the complete list would be much longer. Remember
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too that some functions are implemented with an underscore in
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their name and <function>#define</function>d to that name in
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the MS headers. So you may need to find out the name by
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examining <filename>dlls/msvcrt/msvcrt.spec</filename> to get
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the correct name for your <function>@ignore</function> entry.
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</para>
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</sect1>
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<sect1 id="porting-compiling">
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<title id="porting-compiling.title">Compiling Problems</title>
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<para>
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If you get undefined references to Win32 API calls when
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building your application: if you have a VC++
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<filename>.dsp</filename> file, check it for all the
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<filename>.lib</filename> files it imports, and add them to
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your applications <filename>.spec</filename>
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file. <command>winebuild</command> gives you a warning for
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unused imports so you can delete the ones you don't need
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later. Failing that, just import all the DLL's you can find in
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the <filename>dlls/</filename> directory of the Wine source
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tree.
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</para>
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<para>
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If you are missing GUIDs at the link stage, add
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<parameter>-lwine_uuid</parameter> to the link line.
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</para>
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<para>
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gcc is more strict than VC++, especially when compiling
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C++. This may require you to add casts to your C++ to prevent
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overloading ambiguities between similar types (such as two
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overloads that take int and char respectively).
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</para>
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<para>
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If you come across a difference between the Windows headers
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and Wine's that breaks compilation, try asking for help on
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<email>wine-devel@winehq.org</email>.
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</para>
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</sect1>
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<sect1 id="init-problems">
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<title id="init-problems.title">Initialization problems</title>
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<para>
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Initialization problems occur when the application calls the Win32 API
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before Winelib has been initialized. How can this happen?
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</para>
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<para>
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Winelib is initialized by the application's <function>main</function>
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before it calls the regular <function>WinMain</function>. But, in C++,
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the constructors of static class variables are called before the
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<function>main</function> (by the module's initializer). So if such
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a constructor makes calls to the Win32 API, Winelib will not be
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initialized at the time of the call and you may get a crash. This
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problem is much more frequent in C++ because of these class
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constructors but could also, at least in theory, happen in C if you
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were to specify an initializer making calls to Winelib. But of
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course, now that you are aware of this problem you won't do it :-).
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</para>
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<para>
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Further compounding the problem is the fact that Linux's (GNU's?)
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current dynamic library loader does not call the module
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initializers in their dependency order. So even if Winelib were to
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have its own initializer there would be no guarantee that it would be
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called before the initializer of the library containing this static
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variable. Finally even if the variable is in a library that your
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application links with, that library's initializer may be called
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before Winelib has been initialized. One such library is the MFC.
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</para>
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<para>
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The current workaround is to move all the application's code in a
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library and to use a small Winelib application to dynamically load
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this library. Tus the initialization sequence becomes:
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</para>
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<itemizedlist>
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<listitem>
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<para>
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the wrapper application starts.
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</para>
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</listitem>
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<listitem>
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<para>
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its empty initializer is run.
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</para>
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</listitem>
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<listitem>
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<para>
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its <function>main</function> is run. Its first task is to
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initialize Winelib.
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</para>
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</listitem>
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<listitem>
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<para>
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it then loads the application's main library, plus all its
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dependent libraries.
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</para>
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</listitem>
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<listitem>
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<para>
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which triggers the execution of all these libraries initializers
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in some unknown order. But all is fine because Winelib has
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already been initialized anyway.
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</para>
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</listitem>
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<listitem>
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<para>
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finally the main function calls the <function>WinMain</function>
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of the application's library.
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</para>
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</listitem>
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</itemizedlist>
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<para>
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This may sound complex but Winemaker makes it simple. Just specify
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<option>--wrap</option> or <option>--mfc</option> on the command line
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and it will adapt its makefiles to build the wrapper and the
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application library.
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</para>
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</sect1>
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<sect1 id="com-support">
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<title id="com-support.title">VC's native COM support</title>
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<para>
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don't use it,
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guide on how to replace it with normal C++ code (yes, how???):
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extracting a .h and .lib from a COM DLL
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Can '-fno-rtti' be of some use or even required?
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</para>
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</sect1>
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<sect1 id="SEH">
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<title id="SEH.title">SEH</title>
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<para>
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how to modify the syntax so that it works both with gcc's macros and Wine's macros,
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is it even possible?
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</para>
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</sect1>
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<sect1 id="others">
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<title id="others.title">Others</title>
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<para>
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-fpermissive and -fno-for-scope,
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maybe other options
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</para>
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</sect1>
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</chapter>
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sgml-parent-document:("winelib-user.sgml" "book" "chapter" "")
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