Archive:PackagingDrafts/MinGW

Introduction

The Fedora MinGW project's mission is to provide an excellent development environment for Fedora users who wish to cross-compile their programs to run on Windows, minimizing the need to use Windows at all. In the past developers have had to port and compile all of the libraries and tools they have needed, and this huge effort has happened independently many times over. We aim to eliminate duplication of work for application developers by providing a range of libraries and development tools which have already been ported to the cross-compiler environment. This means that developers will not need to recompile the application stack themselves, but can concentrate just on the changes needed to their own application.

Note that when deciding to contribute a new library to the Fedora MinGW project, it is advisable to start with our example specfile: http://hg.et.redhat.com/misc/fedora-mingw--devel/?fl=7e95a9b24e2d;file=example/mingw32-example.spec

Track Fedora native package versions

In general terms, MinGW packages which provide cross-compiled versions of packages already natively available in Fedora, should follow the native Fedora package as closely as possible. This means they should stay at the same version, include all the same patches as the native Fedora package, and be built with the same configuration options.

The MinGW SIG have written an RPM comparison tool which makes it possible to compare MinGW packages with the Fedora native packages, in order to determine whether versions, patches and configuration are aligned.

Follow Fedora policy

MinGW packages must follow Fedora policy, except where noted in this document. MinGW packages go through the same review process, CVS admin process etc as other Fedora packages.

Package naming

Packages should be named by prefixing the upstream package name with mingw32-

Base packages

The base packages provide a root filesystem, base libraries, binutils (basic programs like 'strip', 'ld' etc), the compiler (gcc) and the Win32 API. Packages may need to depend on one or more of these. In particular, almost any conceivable package should depend on mingw32-filesystem and mingw32-runtime.

mingw32-filesystem	Core filesystem directory layout, and RPM macros for spec files. Equivalent to 'filesystem' RPM
mingw32-runtime	Base libraries for core MinGW runtime & development environment. Equivalent to glibc & glibc-devel RPMs
mingw32-binutils	Cross-compiled binutils (utilities like 'strip', 'as', 'ld') which understand Windows executables and DLLs. Equivalent to 'binutils' RPM
mingw32-w32api	Win32 API. A free (public domain) reimplementation of the header files required to link to the Win32 API. No direct equivalent in base Fedora - glibc-devel is closest
mingw32-gcc	GNU compiler collection. Compilers for C and C++ which cross-compile to a Windows target. Equivalent to gcc RPM

Filesystem layout

[root]
  |
  +- etc
  |   |
  |   +- rpm
  |       |
  |       +- macros.mingw32
  |
  +- usr
      |
      +- bin   - Links to cross compiler toolchain
      |   |
      |   +- i686-pc-mingw32-cpp
      |   +- i686-pc-mingw32-gcc
      |   +- i686-pc-mingw32-g++
      |   +- ... etc..
      |
      +- lib
      |   |
      |   +- rpm
      |       |
      |       +- mingw32-defs   - custom helper scripts for auto-requires, binary stripping, etc
      |       +- mingw32-find-provides.sh - extra DLL names
      |       +- mingw32-find-requires.sh - discover required DLL names
      |
      +- i686-pc-mingw32  - root of mingw toolchain and binaries - see next diagram

/usr/i686-pc-mingw32
  |
  +- bin  - Cross compiler toolchain  
  |   |
  |   +- cpp
  |   +- gcc
  |   +- g++
  |   +- ... etc ...
  |
  +- lib  - Cross compiler toolchain support libraries / files
  |
  +- sys-root  - root for cross compiled binaries
      |
      +- mingw
          |
          +- bin     - cross-compiled binaries & runtime DLL parts
          +- doc     - documentation
          +- include - include files for cross compiled libs
          +- lib     - cross-compiled static libraries & linktime DLL parts
          |   |
          |   +- pkgconfig  - pkg-config definitions for libraries
          |
          +- share
              |
              +- man

Filenames of the cross-compilers and binutils

The cross-compilers and binutils are Fedora binaries and are therefore placed in %{_bindir} (ie. /usr/bin) according to the FHS and Fedora guidelines.

The cross-compilers and binutils which generate i686 binaries for Windows are named:

%{_bindir}/i686-pc-mingw32-gcc
%{_bindir}/i686-pc-mingw32-g++
%{_bindir}/i686-pc-mingw32-ld
%{_bindir}/i686-pc-mingw32-as
%{_bindir}/i686-pc-mingw32-strip
etc.

The same binaries are present in %{_prefix}/i686-pc-mingw32/bin without any prefix in the name, ie:

%{_prefix}/i686-pc-mingw32/bin/gcc
%{_prefix}/i686-pc-mingw32/bin/g++
%{_prefix}/i686-pc-mingw32/bin/ld
%{_prefix}/i686-pc-mingw32/bin/as
%{_prefix}/i686-pc-mingw32/bin/strip
etc.

Naming of the root filesystem

The root filesystem contains Windows executables and DLLs and any other Windows-only files. It is necessary both because we need to store Windows libraries in order to link further libraries which depend on them, and also because MinGW requires a root filesystem location. The location (for i686 target) is provided by the macro:

%{_mingw32_sysroot}   %{_prefix}/i686-pc-mingw32/sys-root

Standard mingw RPM macros

The mingw32-filesystem package provides a number of convenience macros for the cross compiled sysroot directories, and toolchain. It is mandatory to use these macros in all MinGW packages submitted to Fedora.

Toolchain macros

The following macros are for the %build and %install section of the spec

_mingw32_ar	i686-pc-mingw32-ar	cross compiler 'ar' binary
_mingw32_cc	i686-pc-mingw32-gcc	cross compiler 'gcc' binary
_mingw32_cflags	-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions --param=ssp-buffer-size=4
_mingw32_configure	CC="%{_mingw32_cc}" CFLAGS="%{_mingw32_cflags}" ./configure --build=%_build --host=%{_mingw32_host} --target=%{_mingw32_target} --prefix=%{_mingw32_prefix}	standard invocation for autotools 'configure' scripts
_mingw32_cpp	i686-pc-mingw32-gcc -E	cross compiler 'cpp' binary
_mingw32_host	i686-pc-mingw32	Host platform for build
_mingw32_objdump	i686-pc-mingw32-objdump	cross compiler 'objdump' binary
_mingw32_ranlib	i686-pc-mingw32-ranlib	cross compiler 'ranlib' binary
_mingw32_strip	i686-pc-mingw32-strip	cross compiler 'strip' binary
_mingw32_target	i686-pc-mingw32	Target platform for build

Filesystem location macros

The following macros are for use in %build, %install and %files sections of the RPM spec

_mingw32_bindir	%{_mingw32_prefix}/bin	Location of Windows executables.
_mingw32_datadir	%{_mingw32_prefix}/share	Shared data used under Windows.
_mingw32_docdir	%{_mingw32_prefix}/share/doc	Documentation.
_mingw32_infodir	%{_mingw32_prefix}/share/info	Info files (see note below).
_mingw32_includedir	%{_mingw32_prefix}/include	Header files used when cross-compiling for Windows.
_mingw32_libdir	%{_mingw32_prefix}/lib	Windows libraries (see sections below).
_mingw32_libexecdir	%{_mingw32_prefix}/libexec
_mingw32_mandir	%{_mingw32_prefix}/share/man	Man pages (see note below).
_mingw32_prefix	%{_mingw32_sysroot}/mingw	Windows equivalent of %{_prefix}, required by MinGW.
_mingw32_sbindir	%{_mingw32_prefix}/sbin
_mingw32_sysconfdir	%{_mingw32_prefix}/etc	Configuration files used when running under Windows.
_mingw32_sysroot	%{_prefix}/i686-pc-mingw32/sys-root	Windows system root.

Dependencies

If a package contains binaries which depend on a DLL provided by another package, these dependencies should be expressed in the form:

mingw32(foo.dll)

where foo.dll is the name of the DLL. The name must be converted to lowercase because Windows binaries contain case insensitive dependencies.

All packages should depend on mingw32-filesystem.

Correct dependency generation is done automatically. Packagers should include these lines in all library packages:

%define _use_internal_dependency_generator 0
%define __find_requires %{_mingw32_findrequires}
%define __find_provides %{_mingw32_findprovides}

All specfiles should BuildRequire at least:

BuildRequires:  mingw32-filesystem >= minimum-version

and any other BuildRequires that they need.

Build architecture

All packages should have:

BuildArch: noarch

unless they contain Fedora native executables.

Libraries (DLLs)

All libraries must be built as DLLs.

Because of the peculiarity of Windows, DLLs are stored in the %{_mingw32_bindir} directory, along with a control file in the %{_mingw32_libdir} directory. For example, for a library called foo there would be:

%{_mingw32_bindir}/foo.dll
%{_mingw32_bindir}/foo.def
%{_mingw32_libdir}/foo.dll.a
%{_mingw32_libdir}/foo.la

All files are required in those locations in order to link successfully, except that the .def file is not always built by libtool for reasons unknown, and the .dll may contain a version number although not always (eg. foo-0.dll).

Do not use %{_mingw32_bindir}/* or %{_mingw32_libdir}/* in %files section

The %files section must list DLLs separately. Packages must NOT use %{_mingw32_bindir}/* or %{_mingw32_libdir}/*

The reason for this is that libtool is very fragile and will give up on building a DLL very easily. Therefore we force the name of the DLL to be listed explicitly in the %files section in order to catch this during RPM builds.

Manpages and info files

If manpages or info files are simply duplicates of equivalent documentation found in Fedora native packages, then they should not be packaged in the MinGW package.

Static libraries

In accordance with ordinary Fedora policy, static libraries should not be built, and if they are then they should be placed in a -static subpackage.

The exception is the base package mingw32-w32api which contains static libraries that are required for GCC to create executables.

Stripping

Libraries and executables should be stripped. This is done correctly and automatically if the spec file includes these lines:

%define __strip %{_mingw32_strip}
%define __objdump %{_mingw32_objdump}

(Note that if __strip and __objdump are not overridden in the specfile then this can sometimes cause Windows binaries to be corrupted).