Coding Practice

This chapter describes the relevant coding practices in Wine, that you should be aware of before doing any serious development in Wine.

Some notes about style

In the time since the Wine project was started in 1993, its developers have settled on the following general style conventions. These conventions are merely matters of taste; although some of them were once required for compiler compatibility, the current standards for compiler compatibility are documented in the Writing portable code section below.

Some maintained subsystems use different styles, some of which conflict with the below. In this case you should try to conform to the existing style. At the same time, some old or unmaintained code uses style that conflicts with the below, and in that case the style is seen as ugly and we'd prefer to change it. On the other hand, patches which do nothing but change style are unnecessary noise, not worthwhile, and should be avoided.

The following styles are encouraged in general:

Above all, please use a consistent style in your own changes
Use 4-space indentation instead of tabs
Avoid very long lines (there is no hard limit, the preferred length is 100, but 120 or 80 chars are fine too)
Use only slash-star comments, never slash-slash comments (e.g. write /* */ instead of//)
Use snake_case for internal variables instead of camelCase or TitleCase
Prefer asterisks to declare pointers instead of the P and LP typedefs (e.g. write DWORD * instead of LPDWORD)
Asterisks should stick to the variable, not the type (e.g. write int *foo instead of int* foo)
Limit type casts as much as possible (e.g. don't cast a void * to a DWORD * or vice-versa)
Don't use Hungarian notation (e.g. write char *important_buffer instead of char *pImportantBuffer)
Always put braces on a separate line. Braces should not be indented relative to the previous line. This applies to all braces: control flow, functions, type definitions, and initializers.
- Exception: an array or struct initializer (including as part of another initializer) can be specified on one line if it's short enough.
- Exception: in a do-while statement, the "while" statement should be placed on the same line as the closing brace, so that it's clear it's not a standalone "while".
Write hexadecimal constants and variable suffixes in all lowercase (e.g. 0xcafe1234u)
Put spaces around arithmetic and boolean operators (e.g. write (1 + 2) * 3 instead of (1+2)*3)
Use the ARRAY_SIZE macro where appropriate
Remove trailing whitespace from your changes, but don't change whitespace in other lines
Comment out code with if (0), to ensure that the code compiles:

/* note about reason for commenting block */
if (0)
{
    code
    code /* comments */
    code
}

Use void when declaring or defining parameter-less functions:

int foo();                      /* Incorrect */
int foo() { }                   /* Also incorrect */

int foo(void);                  /* Much better */
int foo(void) { }               /* Also much better */

Declarations cannot follow statements; this will trigger a compiler warning. Declarations in a for loop initializer are fine, though.

Preferred D3D coding style

Direct3D and DirectShow enforce a more restrictive coding style than most of the rest of Wine. The following describes Direct3D coding style. Note that many of these principles are applicable elsewhere.

Describe exactly what you're changing in the patch subject line instead of, e.g., a generic 'fix something'.
Trace messages on function entry should include variable names. This makes debugging much easier, as you then don't have to look up the parameter order.
Use %#x when tracing hexadecimal numbers (e.g. do not use %x, 0x%x, %08x, etc.). We want the "0x" prefix so it's always clear the number is hexadecimal, and %#x is one less character than 0x#x.
Trace floats using %.8e, and doubles using %.16e. This always gives enough precision to determine the unique number.
Always end trace messages with a period.
Always use 8 space indentation when continuing a previous line (instead of e.g. trying to align to the first function parameter). This avoids wasting space when a continuation must begin late in the line. For example:

    TRACE("output %p, format %s, scanline_ordering %#x.\n",
            output, debug_d3dformat(format_id), scanline_ordering);

When continuing a previous line, || and && should begin the line, rather than ending the previous line. This is a minor visual aid that the line is a continuation of a condition and not a standalone statement.
Don't introduce typedefs, except for function types. Always using e.g. struct and * makes it clearer what kind of object you're dealing with.
Put the body of an if statement on the next line, even if it's short. It can be easy to miss otherwise when reading.
Braces need not be used when an "if" body is only a single line, but if an "if" body has braces, the "else" body should too, and vice versa.
"case" labels should be indented relative to the "switch", and the body of a case label should be indented relative to the label.
An empty line between switch cases is preferred. An exception is if (almost) all of the cases have one-line bodies (i.e. "return X"); in this case it is also acceptable to put the body on the same line as the label.
Use sizeof(*var) in allocations instead of sizeof(type).
Sort variable declarations to a reverse Christmas tree by length.
Always use unsigned types where the type doesn't need to be signed.

Writing portable code

Write code that compiles on recent versions of both GCC and Clang, as well as MSVC if the code is in a PE module. That means:

Avoid compiler extensions:

typeof(D3DCreateBlob) pD3DCreateBlob;                   /* GCC extension */
HRESULT (WINAPI *pD3DCreateBlob)(SIZE_T, ID3DBlob **);  /* Works on both GCC and MSVC */

ch += offset ?: size            /* GCC extension */
ch += offset ? offset : size    /* Works on both GCC and MSVC */

When declaring function pointers, put the calling convention inside the parentheses:

HRESULT WINAPI (*pD3DCreateBlob)(SIZE_T, ID3DBlob **);  /* Works on GCC but not MSVC */
HRESULT (WINAPI *pD3DCreateBlob)(SIZE_T, ID3DBlob **);  /* Works on both GCC and MSVC */

Use types with dependable definitions:

long wrong = 0xcafe1234l;      /* long is 4 bytes in Win64 but 8 bytes in Unix64 */
LONG right = 0xcafe1234;       /* LONG is 4 bytes, the same as int, on both platforms */

Use WCHAR and array syntax for Unicode string literals in non-PE modules (helpful tool):

const WCHAR str1[] = L"Hello";  /* Preferred on PE modules. But it won't compile on non-PE modules. */
const WCHAR str2[] = {          /* Tedious, but correct */
    'H','e','l','l','o',0
};

Don't use designated initializers for nameless structs or unions (it breaks GCC 4.3)
Don't declare a typedef more than once (it breaks GCC 4.3)

There is no strict minimum compiler version. In 2023, Wine's chief maintainer Alexandre Julliard gave the following explanation of Wine's compiler support policy:

Our policy is to not draw arbitrary lines of supported/unsupported. That's true for C standard versions, compiler versions, distros, window managers, graphics cards, etc.

We want to support what our users are actually using. If someone reports an issue with their compiler, we want to look into it. We are not going to reject a report because the compiler is "too old", or out of maintenance, or on a distro we've hever heard of.

That doesn't mean we have to fix everything, there's always a trade-off between the complexity/ugliness of the fix, the number of affected users, the availability of a workaround, etc. But that should be decided based on the actual issue, not on some arbitrary version number cutoff.

So it may be that we want to require support for typedef redefinitions, because avoiding them is ugly. In practice, that would mean that you can't build with gcc 4.3 out of the box. But it does not mean that gcc 4.3 is somehow "unsupported". If someone reports some other issue with gcc 4.3, and that one is easy to fix, we'll still want to fix it.

Quality Assurance

(Or, “How do I get Alexandre to apply my patch quickly so I can build on it and it will not go stale?”)

Make sure your patch applies to the current Git HEAD revisions. If a bunch of patches are committed that may affect whether your patch will apply cleanly then verify that your patch does apply! git fetch; git rebase origin is your friend!

Patches must not break building Wine or cause test failures. Adding dead code should also be avoided.

Save yourself some embarrassment and run your patched code against more than just your current test example. Experience will tell you how much effort to apply here. If there are any conformance tests for the code you're working on, run them and make sure they still pass after your patch is applied. Running tests can be done by running make test. You may need to run make testclean to undo the results of a previous test run. See the “testing” guide for more details on Wine conformance tests.

Porting Wine to new Platforms

This document provides a few tips on porting Wine to your favorite (UNIX-based) operating system.

Why `#ifdef MyOS` is probably a mistake.

Operating systems change. Maybe yours doesn't have the foo.h header, but maybe a future version will have it. If you want to #include <foo.h>, it doesn't matter what operating system you are using; it only matters whether foo.h is there.

Furthermore, operating systems change names or “fork” into several ones. An #ifdef MyOS will break over time.

If you use the feature of autoconf -- the Gnu auto-configuration utility -- wisely, you will help future porters automatically because your changes will test for features, not names of operating systems. A feature can be many things:

existence of a header file
existence of a library function
existence of libraries
bugs in header files, library functions, the compiler, ...

You will need GNU autoconf, which you can get from your friendly GNU mirror. This program takes Wine configure.ac file and produces a configure shell script that users use to configure Wine to their system.

There are exceptions to the “avoid #ifdef MyOS” rule. Wine, for example, needs the internals of the signal stack -- that cannot easily be described in terms of features. Moreover, you cannot use autoconf HAVE_* symbols in Wine headers, as these may be used by Winelib users who may not be using a configure script.

Let's now turn to specific porting problems and how to solve them.

MyOS doesn't have the `foo.h` header!

This first step is to make autoconf check for this header. In configure.ac you add a segment like this in the section that checks for header files (search for “header files”):

AC_CHECK_HEADER(foo.h, AC_DEFINE(HAVE_FOO_H))

If your operating system supports a header file with the same contents but a different name, say bar.h, add a check for that also.

Now you can change

#include <foo.h>

#ifdef HAVE_FOO_H
#include <foo.h>
#elif defined (HAVE_BAR_H)
#include <bar.h>
#endif

If your system doesn't have a corresponding header file even though it has the library functions being used, you might have to add an #else section to the conditional. Avoid this if you can.

You will also need to add #undef HAVE_FOO_H (etc.) to include/config.h.in.

Finish up with autoconf and ./configure.

MyOS doesn't have the `bar` function!

A typical example of this is the memmove function. To solve this problem you would add memmove to the list of functions that autoconf checks for. In configure.ac you search for AC_CHECK_FUNCS and add memmove (you will notice that someone already did this for this particular function).

Secondly, you will also need to add #undef HAVE_BAR to include/config.h.in.

The next step depends on the nature of the missing function.

Case 1:

It's easy to write a complete implementation of the function (memmove belongs to this case).

You add your implementation in misc/port.c surrounded by #ifndef HAVE_MEMMOVE and #endif.

You might have to add a prototype for your function. If so, include/miscemu.h might be the place. Don't forget to protect that definition by #ifndef HAVE_MEMMOVE and #endif also!

Case 2:

A general implementation is hard, but Wine is only using a special case.

An example is the various wait calls used in SIGNAL_child from loader/signal.c. Here we have a multi-branch case on features:

#ifdef HAVE_THIS
...
#elif defined (HAVE_THAT)
...
#elif defined (HAVE_SOMETHING_ELSE)
...
#endif

Note that this is very different from testing on operating systems. If a new version of your operating systems comes out and adds a new function, this code will magically start using it.

Finish up with autoconf and ./configure.

Adding New Languages

This section documents the procedure for adding a new language to the list of languages that Wine can display system menus and forms in. Adding new translations is not hard as it requires no programming knowledge or special skills.

First add the language ID (most often like xx, e.g. fr for French, or xx_YY for country-specific variations, e.g. pt_BR for Brazilian Portuguese ; look in tools/wmc/po.c for a list) in the LINGUAS section of configure.ac, and in po/LINGUAS.

Language dependent resources reside in .po files in the po/ directory. Simply create the language-specific .po file using the wine.pot template:

cp po/wine.pot po/xx.po

and start translating (note the file must use UTF‑8 encoding).

Some notes about style

Preferred D3D coding style

Writing portable code

Quality Assurance

Porting Wine to new Platforms

Why `#ifdef MyOS` is probably a mistake.

MyOS doesn't have the `foo.h` header!

MyOS doesn't have the `bar` function!

Case 1:

Case 2:

Adding New Languages

Preferred D3D coding style

Why #ifdef MyOS is probably a mistake.

MyOS doesn't have the foo.h header!

MyOS doesn't have the bar function!

Case 1:

Case 2: