NOTES FOR THE WINDOWS PLATFORMS

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

 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:

 - 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.

 - 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 https://www.nasm.us,

   is required. Note that NASM is the only supported assembler. Even

   though Microsoft provided assembler is NOT supported, contemporary

   64-bit version is exercised through continuous integration of

   VC-WIN64A-masm target.

 Installation directories

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

 The default installation directories are derived from environment

 variables.

 For VC-WIN32, the following defaults are use:

     PREFIX:      %ProgramFiles(86)%\OpenSSL

     OPENSSLDIR:  %CommonProgramFiles(86)%\SSL

 For VC-WIN64, the following defaults are use:

     PREFIX:      %ProgramW6432%\OpenSSL

     OPENSSLDIR:  %CommonProgramW6432%\SSL

 Should those environment variables not exist (on a pure Win32

 installation for examples), these fallbacks are used:

     PREFIX:      %ProgramFiles%\OpenSSL

     OPENSSLDIR:  %CommonProgramFiles%\SSL

 ALSO NOTE that those directories are usually write protected, even if

 your account is in the Administrators group.  To work around that,

 start the command prompt by right-clicking on it and choosing "Run as

 Administrator" before running 'nmake install'.  The other solution

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

 --prefix and --openssldir when configuring.

 mingw and mingw64

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

 * MSYS2 shell and development environment installation:

   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...

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

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

   example

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

   or

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

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

   packages.

 Independently of the method chosen to build for mingw, the installation

 paths are similar to those used when building with VC-* targets, except

 that in case the fallbacks mentioned there aren't possible (typically

 when cross compiling on Linux), the paths will be the following:

 For mingw:

     PREFIX:      C:/Program Files (x86)/OpenSSL

     OPENSSLDIR   C:/Program Files (x86)/Common Files/SSL

 For mingw64:

     PREFIX:      C:/Program Files/OpenSSL

     OPENSSLDIR   C:/Program Files/Common Files/SSL

 Linking your application

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

 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,

 ADVAPI32.LIB, CRYPT32.LIB and USER32.LIB. Those developing

 non-interactive service applications might feel concerned about

 linking with GDI32.LIB and USER32.LIB, as they are justly associated

 with interactive desktop, which is not available to service

 processes. The toolkit is designed to detect in which context it's

 currently executed, GUI, console app or service, and act accordingly,

 namely whether or not to actually make GUI calls. Additionally those

 who wish to /DELAYLOAD:GDI32.DLL and /DELAYLOAD:USER32.DLL and

 actually keep them off service process should consider implementing

 and exporting from .exe image in question own _OPENSSL_isservice not

 relying on USER32.DLL. E.g., on Windows Vista and later you could:

	__declspec(dllexport) __cdecl BOOL _OPENSSL_isservice(void)

	{   DWORD sess;

	    if (ProcessIdToSessionId(GetCurrentProcessId(),&sess))

	        return sess==0;

	    return FALSE;

	}

 If you link with OpenSSL .DLLs, then you're expected to include into

 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.