So I've been reading online but I'm still very confused. I understand that there are different tools in the Linux-on-Windows world: Msys, Msys2, Cygwin, Mingw and Mingw-64.
Here is what I think I know, and please correct me if I'm wrong:
Mingw aims to simply be a port of the GCC programs to Windows. It creates native Windows binaries and that's it.
Mingw-64 is just a more recent and better supported version of Mingw that also supports Windows 64 bit.
Cygwin, while also including Mingw (?) to support GCC on Windows, provides a POSIX compatibility layer through a DLL that all programs are linked to by default.
MSYS is a fork of Cygwin, but it drops some of the POSIX compatibility efforts. Instead it mostly aims to allow creating native Windows program. But - they will still be dependent on a MSYS DLL being present.
MSYS2 is just a more recent and active version of the less active MSYS.
Is this all true? If it is, here is what I want to validate:
Essentially, I think all I should need for my development is Mingw in order to use GCC to build native Windows applications. I don't need a POSIX layer, and I don't want my program to depend on any DLL apart from the ones that are present on Windows systems anyway. As far as I understand, this is what Mingw offers.
However, somehow I managed to install MSYS (or MSYS2? I'm not sure anymore) on my system. The tutorial I was following early on suggested doing so.
Since it seems MSYS(2) includes Mingw under C:\msys64\mingw64, I just use the Mingw binaries directly from the Windows CMD without going through the MSYS(2) shell program. For example, I just added C:\msys64\mingw64\bin to the PATH and I run gcc from the Windows CMD directly to compile my project.
Is this a valid way to use Mingw? Or am I expected to run into problems?
Does this approach create pure Windows native binaries which should never depend on any MSYS(2)-related DLL?
Is it true that the MSYS(2)-related functionality and dependencies only come into play if I launch the Mingw programs (such as GCC) through the msys2.exe shell program? And so if I want to avoid any MSYS(2) or Cygwin related stuff, and simply use pure Mingw GCC, is it an okay approach to just launch GCC directly under the Mingw directory as described earlier?
Update: I have now checked using Dependency Walker, and running C:\msys64\mingw64\bin\gcc from the MSYS2 shell still creates an .exe with no special dependencies (which is good). So what is this msys-2.0.dll that the MSYS2 docs speak of? And how is using MSYS2 to compile C different than just using Mingw?
You're mostly right about what these projects are. MSYS2 does provide an evironment for POSIX programs like Bash, GNU Make, and other utilities, but it also provides a package manager named pacman that you can use to install lots of other things. In fact, you can use pacman to install a mingw-w64 toolchain.
MSYS2 provides two mingw-w64 toolchains actually: you get a choice of an i686 (32-bit) toolchain which makes native Windows binaries that can run on any Windows computer, or an x86_64 (64-bit) toolchain that makes native Windows binaries that only work on 64-bit Windows. You can install both of these at the same time.
You say "I don't need a POSIX layer", but you might find it useful to be able to write Bash scripts or use POSIX programs provided by MSYS2 like GNU Make when building your native Windows software. This is especially useful if you want to someday build your software on Linux or macOS: it's possible to write a simple Makefile or shell script that works on those platforms and also MSYS2.
C:\msys64\mingw64\bin directly if you want to.ls, grep, make, and tar. The shell and those utilities use the POSIX emulation provided by msys-2.0.dll. The main difference between those MSYS2 launchers is what gets added to your PATH, so you might want to run echo $PATH and env in each of those environments and compare the results.