early-access version 1255

externals/libressl/README.windows

@@ -0,0 +1,65 @@
+# Building
+
+For Windows systems, LibreSSL supports the mingw-w64 toolchain, which can use
+GCC or Clang as the compiler. Contrary to its name, mingw-w64 supports both
+32-bit and 64-bit build environments. If your project already uses mingw-w64,
+then LibreSSL should integrate very nicely. Old versions of the mingw-w64
+toolchain, such as the one packaged with Ubuntu 12.04, may have trouble
+building LibreSSL. Please try it with a recent toolchain if you encounter
+troubles. Cygwin provides an easy method of installing the latest mingw-w64
+cross compilers on Windows.
+
+To configure and build LibreSSL for a 32-bit system, use the following
+build steps:
+
+ CC=i686-w64-mingw32-gcc CPPFLAGS=-D__MINGW_USE_VC2005_COMPAT \
+ ./configure --host=i686-w64-mingw32
+ make
+ make check
+
+For 64-bit builds, use these instead:
+
+ CC=x86_64-w64-mingw32-gcc ./configure --host=x86_64-w64-mingw32
+ make
+ make check
+
+# Why the -D__MINGW_USE_VC2005_COMPAT flag on 32-bit systems?
+
+An ABI change introduced with Microsoft Visual C++ 2005 (also known as
+Visual C++ 8.0) switched time_t from 32-bit to 64-bit. It is important to
+build LibreSSL with 64-bit time_t whenever possible, because 32-bit time_t
+is unable to represent times past 2038 (this is commonly known as the
+Y2K38 problem).
+
+If LibreSSL is built with 32-bit time_t, when verifying a certificate whose
+expiry date is set past 19 January 2038, it will be unable to tell if the
+certificate has expired or not, and thus take the safe stance and reject it.
+
+In order to avoid this, you need to build LibreSSL (and everything that links
+with it) with the -D__MINGW_USE_VC2005_COMPAT flag. This tells mingw-w64 to
+use the new ABI.
+
+64-bit systems always have a 64-bit time_t and are not affected by this
+problem.
+
+# Using Libressl with Visual Studio
+
+A script for generating ready-to-use .DLL and static .LIB files is included in
+the source repository at
+https://github.com/libressl-portable/portable/blob/master/dist-win.sh
+
+This script uses mingw-w64 to build LibreSSL and then uses Visual Studio tools
+to generate compatible library import files ready-to-use with Visual
+Studio projects. Static and dynamic libraries are included. The script uses
+cv2pdb to generate Visual Studio and windbg compatible debug files. cv2pdb is a
+tool developed for the D language and can be found here:
+https://github.com/rainers/cv2pdb
+
+Pre-built Windows binaries are available with LibreSSL releases if you do not
+have a mingw-w64 build environment. Mingw-w64 code is largely, but not 100%,
+compatible with code built from Visual Studio. Notably, FILE * pointers cannot
+be shared between code built for Mingw-w64 and Visual Studio.
+
+As of LibreSSL 2.2.2, Visual Studio Native builds can be produced using CMake.
+This produces ABI-compatible libraries for linking with native code generated
+by Visual Studio.