w64devkit is a Dockerfile that builds from source a small, portable development suite for creating C and C applications on and for x64 Windows. See "Releases" for pre-built, ready-to-use kits.

Included tools:

• Mingw-w64 GCC : compilers, linker, assembler
• GDB : debugger
• GNU Make : standard build tool
• busybox-w32 : standard unix utilities, including sh
• Vim : powerful text editor
• Universal Ctags : source navigation
• NASM : x86 assembler
• Cppcheck : static code analysis

The toolchain includes pthreads, C 11 threads, and OpenMP. All included runtime components are static. Docker/Podman is not required to use the development kit. It's merely a reliable, clean environment for building the kit itself.

First build the image, then run it to produce a distribution .zip file:

docker build -t w64devkit .
docker run --rm w64devkit >w64devkit.zip

This takes about half an hour on modern systems. You will need an internet connection during the first couple minutes of the build.

The final .zip file contains tools in a typical unix-like configuration. Unzip the contents anywhere. Inside is w64devkit.exe, which launches a console window with the environment configured and ready to go. It is the easiest way to enter the development environment, and requires no system changes. It also sets two extra environment variables: W64DEVKIT_HOME to the installation root and W64DEVKIT to the version.

Alternatively, add the bin/ directory to your path. For example, inside a cmd.exe console or batch script:

set PATH=c:\path\to\w64devkit\bin;%PATH%

Then to start an interactive unix shell:

sh -l

• No installation required. Run it anywhere as any user. Simply delete when no longer needed.

• Fully offline. No internet access is ever required or attempted.

• A focus on static linking all runtime components. The runtime is optimized for size.

• Trivial to build from source, meaning it's easy to tweak and adjust any part of the kit for your own requirements.

• Complements Go for cgo and bootstrapping.

The language runtimes in w64devkit are optimized for size, so it produces particularly small binaries when programs are also optimized for size (-Os) during compilation. If your program only uses the printf family of functions with MSVC-compatible directives (i.e. limited to C89), and you want even smaller binaries, you can avoid embedding the Mingw-w64's improved implementation by setting __USE_MINGW_ANSI_STDIO to 0 before including any headers.

$ cc -Os -D__USE_MINGW_ANSI_STDIO=0 ...

Only C and C are included by default, but w64devkit also has full support for Fortran. To build a Fortran compiler, add fortran to the --enable-languages lines in the Dockerfile.

With a few exceptions, such as Vim's built-in documentation (:help), w64devkit does not include documentation. However, you need not forgo offline documentation alongside your offline development tools. This is a list of recommended, no-cost, downloadable documentation complementing w64devkit's capabilities. In rough order of importance:

• cppreference (HTML), friendly documentation for the C and C standard libraries.

• GCC manuals (PDF, HTML), to reference GCC features, especially built-ins, intrinsics, and command line switches.

• Win32 Help File (CHM) is old, but official, Windows API documentation. Unfortunately much is missing, such as Winsock. (Offline Windows documentation has always been very hard to come by.)

• C and C Standards (drafts) (PDF), for figuring out how corner cases are intended to work.

• Intel Intrinsics Guide (interactive HTML), a great resource when working with SIMD intrinsics. (Search for "Download" on the left.)

• GNU Make manual (PDF, HTML)

• GNU Binutils manuals (PDF, HTML), particularly ld and as.

• GDB manual (PDF)

• BusyBox man pages (TXT), though everything here is also available via -h option inside w64devkit.

• NASM manual (PDF)

• Intel Software Developer Manuals (PDF), for referencing x86 instructions, when either studying compiler output with objdump, or writing assembly with nasm or as.

Except for the standard libraries and Win32 import libraries, w64devkit does not include libraries, but you can install additional libraries such that the toolchain can find them naturally. There are three options:

1. Install it under the sysroot at w64devkit/$ARCH/. The easiest option, but will require re-installation after upgrading w64devkit. If it defines .pc files, the pkg-config command will automatically find and use them.

2. Append its installation directory to your CPATH and LIBRARY_PATH environment variables. Use ; to delimit directories. You would likely do this in your .profile.

3. If it exists, append its pkgconfig directory to the PKG_CONFIG_PATH environment variable, then use the pkg-config command as usual. Use ; to delimit directories

Both (1) and (3) are designed to work correctly even if w64devkit or the libraries have paths containing spaces.

Use --library=windows for programs calling the Win32 API directly, which adds additional checks. In general, the following configuration is a good default for programs developed using w64devkit:

$ cppcheck --quiet -j$(nproc) --library=windows \
           --suppress=uninitvar --enable=portability,performance .

A "strict" check that is more thorough, but more false positives:

$ cppcheck --quiet -j$(nproc) --library=windows \
      --enable=portability,performance,style \
      --suppress=uninitvar --suppress=unusedStructMember \
      --suppress=constVariable --suppress=shadowVariable \
      --suppress=variableScope --suppress=constParameter \
      --suppress=shadowArgument --suppress=knownConditionTrueFalse .

$HOME can be set through the adjacent w64devkit.ini configuration, and may even be relative to the w64devkit/ directory. This is useful for encapsulating the entire development environment, with home directory, on removable, even read-only, media. Use a .profile in the home directory to configure the environment further.

I'd love to include Git, but unfortunately Git's build system doesn't quite support cross-compilation. A decent alternative would be Quilt, but it's written in Bash and Perl.

Neither Address Sanitizer (ASan) nor Thread Sanitizer (TSan) has been ported to Mingw-w64 (also), but Undefined Behavior Sanitizer (UBSan) works perfectly under GDB. With both -fsanitize=undefined and -fsanitize-undefined-trap-on-error, GDB will break precisely on undefined behavior, and it does not require linking with libsanitizer.

The kit includes a unique debugbreak command. It causes all debugee processes to break in the debugger, like using Windows' F12 debugger hotkey. This is especially useful for console subsystem programs.

Since the build environment is so stable and predicable, it would be great for the .zip to be reproducible, i.e. builds by different people are bit-for-bit identical. There are multiple reasons why this is not currently the case, the least of which are timestamps in the .zip file.

When distributing binaries built using w64devkit, your .exe will include parts of this distribution. For the GCC runtime, including OpenMP, you're covered by the GCC Runtime Library Exception so you do not need to do anything. However the Mingw-w64 runtime has the usual software license headaches and you may need to comply with various BSD-style licenses depending on the functionality used by your program: MinGW-w64 runtime licensing and winpthreads license. To make this easy, w64devkit includes the concatenated set of all licenses in the file COPYING.MinGW-w64-runtime.txt, which should be distributed with your binaries.