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136 lines
4.0 KiB
Plaintext
136 lines
4.0 KiB
Plaintext
What is this?
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------------
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This note is a short description of
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* How to port Wine to your favourite operating system
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* Why you probably shouldn't use "#ifdef MyOS"
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* What to do instead.
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This document does not say a thing about how to port Wine to non-386
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operating systems, though. You would need a CPU emulator. Let's get
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Wine into a better shape on 386 first, OK?
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Why "#ifdef MyOS" is probably a mistake.
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---------------------------------------
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Operating systems change. Maybe yours doesn't have the "foo.h"
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header, but maybe a future version will have it. If you want
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to "#include <foo.h>", it doesn't matter what operating system
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you are using; it only matters whether "foo.h" is there.
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Furthermore, operating systems change names or "fork" into
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several ones. An "#ifdef MyOs" will break over time.
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If you use the feature of Autoconf, the Gnu auto-configuration
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utility wisely, you will help future porters automatically
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because your changes will test for _features_, not names of
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operating systems. A feature can be many things:
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* existance of a header file
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* existance of a library function
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* existance of libraries
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* bugs in header files, library functions, the compiler, ...
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* (you name it)
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You will need Gnu Autoconf, which you can get from your
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friendly Gnu mirror. This program takes Wine's "configure.in"
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file and produces a "configure" shell script that users use to
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configure Wine to their system.
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There _are_ exceptions to the "avoid #ifdef MyOS" rule. Wine,
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for example, needs the internals of the signal stack -- that
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cannot easily be described in terms of features.
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Let's now turn to specific porting problems and how to solve
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them.
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MyOS doesn't have the `foo.h' header!
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------------------------------------
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This first step is to make Autoconf check for this header.
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In configure.in you add a segment like this in the section
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that checks for header files (search for "header files"):
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AC_CHECK_HEADER(foo.h, AC_DEFINE(HAVE_FOO_H))
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If your operating system supports a header file with the
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same contents but a different name, say bar.h, add a check
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for that also.
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Now you can change
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#include <foo.h>
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to
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#ifdef HAVE_FOO_H
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#include <foo.h>
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#elif defined (HAVE_BAR_H)
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#include <bar.h>
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#endif
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If your system doesn't have a corresponding header file even
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though it has the library functions being used, you might
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have to add an "#else" section to the conditional. Avoid
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this if you can.
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You will also need to add "#undef HAVE_FOO_H" (etc.) to
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include/config.h.in
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Finish up with "make configure" and "./configure".
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MyOS doesn't have the `bar' function!
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------------------------------------
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A typical example of this is the `memmove'. To solve this
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problem you would add `memmove' to the list of functions
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that Autoconf checks for. In configure.in you search for
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AC_CHECK_FUNCS and add `memmove'. (You will notice that
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someone already did this for this particular function.)
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Secondly, you will also need to add "#undef HAVE_BAR"
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to include/config.h.in
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The next step depends on the nature of the missing function.
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Case 1: It's easy to write a complete implementation of the
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function. (`memmove' belongs to this case.)
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You add your implementation in misc/port.c surrounded by
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"#ifndef HAVE_MEMMOVE" and "#endif".
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You might have to add a prototype for your function. If so,
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include/miscemu.h might be the place. Don't forget to protect
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that definition by "#ifndef HAVE_MEMMOVE" and "#endif" also!
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Case 2: A general implementation is hard, but Wine is only using
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a special case.
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An example is the various "wait" calls used in SIGNAL_child
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from loader/signal.c. Here we have a multi-branch case on
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features:
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#ifdef HAVE_THIS
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...
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#elif defined (HAVE_THAT)
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...
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#elif defined (HAVE_SOMETHING_ELSE)
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...
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#endif
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Note that this is very different from testing on operating
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systems. If a new version of your operating systems comes
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out and adds a new function, this code will magically start
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using it.
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Finish up with "make configure" and "./configure".
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