NOTES.WIN: classify targets to "native" and "hosted" and restructure.

 NOTES FOR THE WINDOWS PLATFORMS

 ===============================

 Requirement details for native (Visual C++) builds

 --------------------------------------------------

 Windows targets can be classified as "native", ones that use Windows API

 directly, and "hosted" which rely on POSIX-compatible layer. "Native"

 targets are VC-* (where "VC" stems from abbreviating Microsoft Visual C

 compiler) and mingw[64]. "Hosted" platforms are Cygwin and MSYS[2]. Even

 though the latter is not directly supported by OpenSSL Team, it's #1

 popular choice for building MinGW targets. In the nutshell MinGW builds

 are always cross-compiled. On Linux and Cygwin they look exactly as such

 and require --cross-compile-prefix option. While on MSYS[2] it's solved

 rather by placing gcc that produces "MinGW binary" code 1st on $PATH.

 This is customarily source of confusion. "Hosted" applications "live" in

 emulated file system name space with POSIX-y root, mount points, /dev

 and even /proc. Confusion is intensified by the fact that MSYS2 shell

 (or rather emulated execve(2) call) examines the binary it's about to

 start, and if it's found *not* to be linked with MSYS2 POSIX-y thing,

 command line arguments that look like file names get translated from

 emulated name space to "native". For example '/c/some/where' becomes

 'c:\some\where', '/dev/null' - 'nul'. This creates an illusion that

 there is no difference between MSYS2 shell and "MinGW binary", but

 there is. Just keep in mind that "MinGW binary" "experiences" Windows

 system in exactly same way as one produced by VC, and in its essence

 is indistinguishable from the latter. (Which by the way is why

 it's referred to in quotes here, as "MinGW binary", it's just as

 "native" as it can get.)

 Visual C++ builds, a.k.a. VC-*

 ==============================

 Requirement details

 -------------------

 In addition to the requirements and instructions listed in INSTALL,

 these are required as well:

 - You need Perl.  We recommend ActiveState Perl, available from

 - Perl. We recommend ActiveState Perl, available from

   https://www.activestate.com/ActivePerl. Another viable alternative

   appears to be Strawberry Perl, http://strawberryperl.com.

   You also need the perl module Text::Template, available on CPAN.

   Please read NOTES.PERL for more information.

 - You need a C compiler.  OpenSSL has been tested to build with these:

   * Visual C++

 - Microsoft Visual C compiler. Since we can't test them all, there is

   unavoidable uncertainty about which versions are supported. Latest

   version along with couple of previous are certainly supported. On

   the other hand oldest one is known not to work. Everything between

   falls into best-effort category.

 - Netwide Assembler, a.k.a. NASM, available from http://www.nasm.us,

   is required if you intend to utilize assembler modules. Note that NASM

   supported.

 Visual C++ (native Windows)

 ---------------------------

 Installation directories

 ------------------------

 The default installation directories are derived from environment

 variables.

 is, of course, to choose a different set of directories by using

 --prefix and --openssldir when configuring.

 GNU C (Cygwin)

 --------------

 Cygwin implements a Posix/Unix runtime system (cygwin1.dll) on top of the

 Windows subsystem and provides a bash shell and GNU tools environment.

 Consequently, a make of OpenSSL with Cygwin is virtually identical to the

 Unix procedure.

 To build OpenSSL using Cygwin, you need to:

 * Install Cygwin (see https://cygwin.com/)

 * Install Cygwin Perl and ensure it is in the path. Recall that

   as least 5.10.0 is required.

 * Run the Cygwin bash shell

 Apart from that, follow the Unix instructions in INSTALL.

 NOTE: "make test" and normal file operations may fail in directories

 mounted as text (i.e. mount -t c:\somewhere /home) due to Cygwin

 stripping of carriage returns. To avoid this ensure that a binary

 mount is used, e.g. mount -b c:\somewhere /home.

 It is also possible to create "conventional" Windows binaries that use

 the Microsoft C runtime system (msvcrt.dll or crtdll.dll) using MinGW

 development add-on for Cygwin. MinGW is supported even as a standalone

 setup as described in the following section. In the context you should

 recognize that binaries targeting Cygwin itself are not interchangeable

 with "conventional" Windows binaries you generate with/for MinGW.

 mingw and mingw64

 =================

 * MSYS2 shell and development environment installation:

 GNU C (MinGW/MSYS)

 ------------------

   Download MSYS2 from https://msys2.github.io/ and follow installation

   instructions. Once up and running install even make, perl, (git if

   needed,) mingw-w64-i686-gcc and/or mingw-w64-x86_64-gcc. You should

   have corresponding MinGW items on your start menu, use *them*, not

   generic MSYS2. As implied in opening note, difference between them

   is which compiler is found 1st on $PATH. At this point ./config

   should recognize correct target, roll as if it was Unix...

 * Compiler and shell environment installation:

 * It is also possible to build mingw[64] on Linux or Cygwin by

   configuring with corresponding --cross-compile-prefix= option. For

   example

   MinGW and MSYS are available from http://www.mingw.org/, both are

   required. Run the installers and do whatever magic they say it takes

   to start MSYS bash shell with GNU tools and matching Perl on its PATH.

   "Matching Perl" refers to chosen "shell environment", i.e. if built

   under MSYS, then Perl compiled for MSYS must be used.

     ./Configure mingw --cross-compile-prefix=i686-w64-mingw32- ...

   Alternatively, one can use MSYS2 from https://msys2.github.io/,

   which includes MingW (32-bit and 64-bit).

   or

 * It is also possible to cross-compile it on Linux by configuring

   with './Configure --cross-compile-prefix=i386-mingw32- mingw ...'.

   Other possible cross compile prefixes include x86_64-w64-mingw32-

   and i686-w64-mingw32-.

     ./Configure mingw64 --cross-compile-prefix=x86_64-w64-mingw32- ...

   This naturally implies that you've installed corresponding add-on

   packages.

 Linking your application

 ------------------------

 ========================

 This section applies to non-Cygwin builds.

 This section applies to all "native" builds.

 If you link with static OpenSSL libraries then you're expected to

 additionally link your application with WS2_32.LIB, GDI32.LIB,

 your application code small "shim" snippet, which provides glue between

 OpenSSL BIO layer and your compiler run-time. See the OPENSSL_Applink

 manual page for further details.

 Cygwin, "hosted" environment

 ============================

 Cygwin implements a Posix/Unix runtime system (cygwin1.dll) on top of the

 Windows subsystem and provides a bash shell and GNU tools environment.

 Consequently, a make of OpenSSL with Cygwin is virtually identical to the

 Unix procedure.

 To build OpenSSL using Cygwin, you need to:

 * Install Cygwin (see https://cygwin.com/)

 * Install Cygwin Perl and ensure it is in the path. Recall that

   as least 5.10.0 is required.

 * Run the Cygwin bash shell

 Apart from that, follow the Unix instructions in INSTALL.

 NOTE: "make test" and normal file operations may fail in directories

 mounted as text (i.e. mount -t c:\somewhere /home) due to Cygwin

 stripping of carriage returns. To avoid this ensure that a binary

 mount is used, e.g. mount -b c:\somewhere /home.