Update PCbuild/readme.txt

It now better matches 3.5+ and the new reality of 2.7's PCbuild dir.

PCbuild/readme.txt

+Quick Start Guide
+-----------------
+
+1.  Install Microsoft Visual Studio 2008, any edition.
+2.  Install Microsoft Visual Studio 2010, any edition, or Windows SDK 7.1
+    and any version of Microsoft Visual Studio newer than 2010.
+3.  Install Subversion, and make sure 'svn.exe' is on your PATH.
+4.  Run "build.bat -e" to build Python in 32-bit Release configuration.
+5.  (Optional, but recommended) Run the test suite with "rt.bat -q".
+
+
 Building Python using MSVC 9.0 via MSBuild
 ------------------------------------------
 
@@ -27,43 +38,63 @@ MSVCRT90.dll.
 
 For other Windows platforms and compilers, see ../PC/readme.txt.
 
-All you need to do is open the workspace "pcbuild.sln" in Visual Studio,
-select the desired combination of configuration and platform and eventually
-build the solution. Unless you are going to debug a problem in the core or
-you are going to create an optimized build you want to select "Release" as
-configuration.
-
-The PCbuild directory is compatible with all versions of Visual Studio from
-VS C++ Express Edition over the standard edition up to the professional
-edition. However the express edition does not support features like solution
-folders or profile guided optimization (PGO). The missing bits and pieces
-won't stop you from building Python.
-
-The solution is configured to build the projects in the correct order. "Build
-Solution" or F7 takes care of dependencies except for x64 builds. To make
-cross compiling x64 builds on a 32bit OS possible the x64 builds require a
-32bit version of Python.
-
-NOTE:
-   You probably don't want to build most of the other subprojects, unless
-   you're building an entire Python distribution from scratch, or
-   specifically making changes to the subsystems they implement, or are
-   running a Python core buildbot test slave; see SUBPROJECTS below)
-
-When using the Debug setting, the output files have a _d added to
-their name:  python27_d.dll, python_d.exe, parser_d.pyd, and so on. Both
-the build and rt batch files accept a -d option for debug builds.
-
-The 32bit builds end up in the solution folder PCbuild while the x64 builds
-land in the amd64 subfolder. The PGI and PGO builds for profile guided
-optimization end up in their own folders, too.
+All you need to do to build is open the solution "pcbuild.sln" in Visual
+Studio, select the desired combination of configuration and platform,
+then build with "Build Solution".  You can also build from the command
+line using the "build.bat" script in this directory; see below for
+details.  The solution is configured to build the projects in the correct
+order.
+
+The solution currently supports two platforms.  The Win32 platform is
+used to build standard x86-compatible 32-bit binaries, output into this
+directory.  The x64 platform is used for building 64-bit AMD64 (aka
+x86_64 or EM64T) binaries, output into the amd64 sub-directory.  The
+Itanium (IA-64) platform is no longer supported.
+
+Four configuration options are supported by the solution:
+Debug
+    Used to build Python with extra debugging capabilities, equivalent
+    to using ./configure --with-pydebug on UNIX.  All binaries built
+    using this configuration have "_d" added to their name:
+    python27_d.dll, python_d.exe, parser_d.pyd, and so on.  Both the
+    build and rt (run test) batch files in this directory accept a -d
+    option for debug builds.  If you are building Python to help with
+    development of CPython, you will most likely use this configuration.
+PGInstrument, PGUpdate
+    Used to build Python in Release configuration using PGO, which
+    requires Professional Edition of Visual Studio 2008.  See the
+    "Profile Guided Optimization" section below for more information.
+    Build output from each of these configurations lands in its own
+    sub-directory of this directory.  The official Python releases may
+    be built using these configurations.
+Release
+    Used to build Python as it is meant to be used in production
+    settings, though without PGO.
+
+
+Building Python using the build.bat script
+----------------------------------------------
+
+In this directory you can find build.bat, a script designed to make
+building Python on Windows simpler.  This script will use the env.bat
+script to detect one of Visual Studio 2015, 2013, 2012, or 2010, any of
+which contains a usable version of MSBuild.
+
+By default, build.bat will build Python in Release configuration for
+the 32-bit Win32 platform.  It accepts several arguments to change
+this behavior, try `build.bat -h` to learn more.
+
 
 Legacy support
 --------------
 
 You can find build directories for older versions of Visual Studio and
-Visual C++ in the PC directory. The legacy build directories are no longer
-actively maintained and may not work out of the box.
+Visual C++ in the PC directory.  The project files in PC/VS9.0/ are
+specific to Visual Studio 2008, and will be fully supported for the life
+of Python 2.7.
+
+The following legacy build directories are no longer maintained and may
+not work out of the box.
 
 PC/VC6/
     Visual C++ 6.0
@@ -73,7 +104,7 @@ PC/VS8.0/
     Visual Studio 2005 (8.0)
 
 
-C RUNTIME
+C Runtime
 ---------
 
 Visual Studio 2008 uses version 9 of the C runtime (MSVCRT9).  The executables
@@ -88,187 +119,204 @@ it in the same directory.  For compatibility with older systems, one should
 also set the PATH to this directory so that the dll can be found.
 For more info, see the Readme in the VC/Redist folder.
 
-SUBPROJECTS
------------
-These subprojects should build out of the box.  Subprojects other than the
-main ones (pythoncore, python, pythonw) generally build a DLL (renamed to
-.pyd) from a specific module so that users don't have to load the code
-supporting that module unless they import the module.
 
+Sub-Projects
+------------
+
+The CPython project is split up into several smaller sub-projects which
+are managed by the pcbuild.sln solution file.  Each sub-project is
+represented by a .vcxproj and a .vcxproj.filters file starting with the
+name of the sub-project.  These sub-projects fall into a few general
+categories:
+
+The following sub-projects represent the bare minimum required to build
+a functioning CPython interpreter.  If nothing else builds but these,
+you'll have a very limited but usable python.exe:
 pythoncore
     .dll and .lib
 python
     .exe
+
+These sub-projects provide extra executables that are useful for running
+CPython in different ways:
 pythonw
-    pythonw.exe, a variant of python.exe that doesn't pop up a DOS box
+    pythonw.exe, a variant of python.exe that doesn't open a Command
+    Prompt window
+pylauncher
+    py.exe, the Python Launcher for Windows, see
+        http://docs.python.org/3/using/windows.html#launcher
+pywlauncher
+    pyw.exe, a variant of py.exe that doesn't open a Command Prompt
+    window
+
+The following sub-projects are for individual modules of the standard
+library which are implemented in C; each one builds a DLL (renamed to
+.pyd) of the same name as the project:
+_ctypes
+_ctypes_test
+_elementtree
+_hashlib
+_msi
+_multiprocessing
 _socket
-    socketmodule.c
 _testcapi
-    tests of the Python C API, run via Lib/test/test_capi.py, and
-    implemented by module Modules/_testcapimodule.c
 pyexpat
-    Python wrapper for accelerated XML parsing, which incorporates stable
-    code from the Expat project:  http://sourceforge.net/projects/expat/
 select
-    selectmodule.c
 unicodedata
-    large tables of Unicode data
 winsound
-    play sounds (typically .wav files) under Windows
 
-Python-controlled subprojects that wrap external projects:
+There is also a w9xpopen project to build w9xpopen.exe, which is used
+for platform.popen() on platforms whose COMSPEC points to 'command.com'.
+
+The following Python-controlled sub-projects wrap external projects.
+Note that these external libraries are not necessary for a working
+interpreter, but they do implement several major features.  See the
+"Getting External Sources" section below for additional information
+about getting the source for building these libraries.  The sub-projects
+are:
 _bsddb
-    Wraps Berkeley DB 4.7.25, which is currently built by _bsddb.vcproj.
-    project.
+    Python wrapper for Berkeley DB version 4.7.25.
+    Homepage:
+        http://www.oracle.com/us/products/database/berkeley-db/
+_bz2
+    Python wrapper for version 1.0.6 of the libbzip2 compression library
+    Homepage:
+        http://www.bzip.org/
+_ssl
+    Python wrapper for version 1.0.2d of the OpenSSL secure sockets
+    library, which is built by ssl.vcxproj
+    Homepage:
+        http://www.openssl.org/
+
+    Building OpenSSL requires nasm.exe (the Netwide Assembler), version
+    2.10 or newer from
+        http://www.nasm.us/
+    to be somewhere on your PATH.  More recent versions of OpenSSL may
+    need a later version of NASM. If OpenSSL's self tests don't pass,
+    you should first try to update NASM and do a full rebuild of
+    OpenSSL.  If you use the PCbuild\get_externals.bat method
+    for getting sources, it also downloads a version of NASM which the
+    libeay/ssleay sub-projects use.
+
+    The libeay/ssleay sub-projects expect your OpenSSL sources to have
+    already been configured and be ready to build.  If you get your sources
+    from svn.python.org as suggested in the "Getting External Sources"
+    section below, the OpenSSL source will already be ready to go.  If
+    you want to build a different version, you will need to run
+
+       PCbuild\prepare_ssl.py path\to\openssl-source-dir
+
+    That script will prepare your OpenSSL sources in the same way that
+    those available on svn.python.org have been prepared.  Note that
+    Perl must be installed and available on your PATH to configure
+    OpenSSL.  ActivePerl is recommended and is available from
+        http://www.activestate.com/activeperl/
+
+    The libeay and ssleay sub-projects will build the modules of OpenSSL
+    required by _ssl and _hashlib and may need to be manually updated when
+    upgrading to a newer version of OpenSSL or when adding new
+    functionality to _ssl or _hashlib. They will not clean up their output
+    with the normal Clean target; CleanAll should be used instead.
 _sqlite3
-    Wraps SQLite 3.6.21, which is currently built by sqlite3.vcproj.
+    Wraps SQLite 3.6.21, which is itself built by sqlite3.vcxproj
+    Homepage:
+        http://www.sqlite.org/
 _tkinter
-    Wraps the Tk windowing system.  Unlike _bsddb and _sqlite3, there's no
-    corresponding tcltk.vcproj-type project that builds Tcl/Tk from vcproj's
-    within our pcbuild.sln, which means this module expects to find a
-    pre-built Tcl/Tk in either ..\externals\tcltk for 32-bit or
-    ..\externals\tcltk64 for 64-bit (relative to this directory).  See below
-    for instructions to build Tcl/Tk.
-bz2
-    Python wrapper for the libbz2 compression library.  Homepage
-        http://sources.redhat.com/bzip2/
-    Download the source from the python.org copy into the dist
-    directory:
-
-    svn export http://svn.python.org/projects/external/bzip2-1.0.6
-
-    ** NOTE: if you use the PCbuild\get_externals.bat approach for
-    obtaining external sources then you don't need to manually get the source
-    above via subversion. **
+    Wraps version 8.5.15 of the Tk windowing system.
+    Homepage:
+        http://www.tcl.tk/
 
-_ssl
-    Python wrapper for the secure sockets library.
+    Tkinter's dependencies are built by the tcl.vcxproj and tk.vcxproj
+    projects.  The tix.vcxproj project also builds the Tix extended
+    widget set for use with Tkinter.
 
-    Get the source code through
+    Those three projects install their respective components in a
+    directory alongside the source directories called "tcltk" on
+    Win32 and "tcltk64" on x64.  They also copy the Tcl and Tk DLLs
+    into the current output directory, which should ensure that Tkinter
+    is able to load Tcl/Tk without having to change your PATH.
 
-    svn export http://svn.python.org/projects/external/openssl-1.0.2d
+    The tcl, tk, and tix sub-projects do not clean their builds with
+    the normal Clean target; if you need to rebuild, you should use the
+    CleanAll target or manually delete their builds.
 
-    ** NOTE: if you use the PCbuild\get_externals.bat approach for
-    obtaining external sources then you don't need to manually get the source
-    above via subversion. **
 
-    The NASM assembler is required to build OpenSSL.  If you use the
-    PCbuild\get_externals.bat script to get external library sources, it also
-    downloads a version of NASM, which the ssl build script will add to PATH.
-    Otherwise, you can download the NASM installer from
-        http://www.nasm.us/
-    and add NASM to your PATH.
+Getting External Sources
+------------------------
+
+The last category of sub-projects listed above wrap external projects
+Python doesn't control, and as such a little more work is required in
+order to download the relevant source files for each project before they
+can be built.  However, a simple script is provided to make this as
+painless as possible, called "get_externals.bat" and located in this
+directory.  This script extracts all the external sub-projects from
+    http://svn.python.org/projects/external
+via Subversion (so you'll need svn.exe on your PATH) and places them
+in ..\externals (relative to this directory).
+
+It is also possible to download sources from each project's homepage,
+though you may have to change folder names or pass the names to MSBuild
+as the values of certain properties in order for the build solution to
+find them.  This is an advanced topic and not necessarily fully
+supported.
+
+The get_externals.bat script is called automatically by build.bat when
+you pass the '-e' option to it.
 
-    You can also install ActivePerl from
-        http://www.activestate.com/activeperl/
-    if you like to use the official sources instead of the files from
-    python's subversion repository. The svn version contains pre-build
-    makefiles and assembly files.
-
-    The build process makes sure that no patented algorithms are included.
-    For now RC5, MDC2 and IDEA are excluded from the build. You may have
-    to manually remove $(OBJ_D)\i_*.obj from ms\nt.mak if the build process
-    complains about missing files or forbidden IDEA. Again the files provided
-    in the subversion repository are already fixed.
-
-    The MSVC project simply invokes PCBuild/build_ssl.py to perform
-    the build.  This Python script locates and builds your OpenSSL
-    installation, then invokes a simple makefile to build the final .pyd.
-
-    build_ssl.py attempts to catch the most common errors (such as not
-    being able to find OpenSSL sources, or not being able to find a Perl
-    that works with OpenSSL) and give a reasonable error message.
-    If you have a problem that doesn't seem to be handled correctly
-    (eg, you know you have ActivePerl but we can't find it), please take
-    a peek at build_ssl.py and suggest patches.  Note that build_ssl.py
-    should be able to be run directly from the command-line.
-
-    build_ssl.py/MSVC isn't clever enough to clean OpenSSL - you must do
-    this by hand.
-
-The subprojects above wrap external projects Python doesn't control, and as
-such, a little more work is required in order to download the relevant source
-files for each project before they can be built.  The easiest way to do this
-is to use the `build.bat` script in this directory to build Python, and pass
-the '-e' switch to tell it to use get_externals.bat to fetch external sources
-and build Tcl/Tk and Tix.  To use get_externals.bat, you'll need to have
-Subversion installed and svn.exe on your PATH.  The script will fetch external
-library sources from http://svn.python.org/external and place them in
-..\externals (relative to this directory).
-
-Building for Itanium
---------------------
-
-Official support for Itanium builds have been dropped from the build. Please
-contact us and provide patches if you are interested in Itanium builds.
-
-Building for AMD64
-------------------
-
-The build process for AMD64 / x64 is very similar to standard builds. You just
-have to set x64 as platform. In addition, the HOST_PYTHON environment variable
-must point to a Python interpreter (at least 2.4), to support cross-compilation.
-
-Building Python Using the free MS Toolkit Compiler
---------------------------------------------------
-
-Microsoft has withdrawn the free MS Toolkit Compiler, so this can no longer
-be considered a supported option. Instead you can use the free VS C++ Express
-Edition.
 
 Profile Guided Optimization
 ---------------------------
 
 The solution has two configurations for PGO. The PGInstrument
-configuration must be build first. The PGInstrument binaries are
-linked against a profiling library and contain extra debug
-information. The PGUpdate configuration takes the profiling data and
-generates optimized binaries.
+configuration must be built first. The PGInstrument binaries are linked
+against a profiling library and contain extra debug information. The
+PGUpdate configuration takes the profiling data and generates optimized
+binaries.
 
-The build_pgo.bat script automates the creation of optimized binaries. It
-creates the PGI files, runs the unit test suite or PyBench with the PGI
-python and finally creates the optimized files.
+The build_pgo.bat script automates the creation of optimized binaries.
+It creates the PGI files, runs the unit test suite or PyBench with the
+PGI python, and finally creates the optimized files.
+
+See
+    http://msdn.microsoft.com/en-us/library/e7k32f4k(VS.90).aspx
+for more on this topic.
 
-http://msdn.microsoft.com/en-us/library/e7k32f4k(VS.90).aspx
 
 Static library
 --------------
 
-The solution has no configuration for static libraries. However it is easy
-it build a static library instead of a DLL. You simply have to set the
-"Configuration Type" to "Static Library (.lib)" and alter the preprocessor
-macro "Py_ENABLE_SHARED" to "Py_NO_ENABLE_SHARED". You may also have to
-change the "Runtime Library" from "Multi-threaded DLL (/MD)" to
-"Multi-threaded (/MT)".
+The solution has no configuration for static libraries. However it is
+easy to build a static library instead of a DLL. You simply have to set
+the "Configuration Type" to "Static Library (.lib)" and alter the
+preprocessor macro "Py_ENABLE_SHARED" to "Py_NO_ENABLE_SHARED". You may
+also have to change the "Runtime Library" from "Multi-threaded DLL
+(/MD)" to "Multi-threaded (/MT)".
+
 
 Visual Studio properties
 ------------------------
 
-The PCbuild solution makes heavy use of Visual Studio property files
-(*.vsprops). The properties can be viewed and altered in the Property
-Manager (View -> Other Windows -> Property Manager).
-
- * debug (debug macro: _DEBUG)
- * pginstrument (PGO)
- * pgupdate (PGO)
-    +-- pginstrument
- * pyd (python extension, release build)
-    +-- release
-    +-- pyproject
- * pyd_d (python extension, debug build)
-    +-- debug
-    +-- pyproject
- * pyproject (base settings for all projects, user macros like PyDllName)
- * release (release macro: NDEBUG)
- * x64 (AMD64 / x64 platform specific settings)
-
-The pyproject propertyfile defines _WIN32 and x64 defines _WIN64 and _M_X64
-although the macros are set by the compiler, too. The GUI doesn't always know
-about the macros and confuse the user with false information.
-
-YOUR OWN EXTENSION DLLs
+The PCbuild solution makes use of Visual Studio property files (*.props)
+to simplify each project. The properties can be viewed in the Property
+Manager (View -> Other Windows -> Property Manager) but should be
+carefully modified by hand.
+
+The property files used are:
+ * python (versions, directories and build names)
+ * pyproject (base settings for all projects)
+ * openssl (used by libeay and ssleay projects)
+ * tcltk (used by _tkinter, tcl, tk and tix projects)
+
+The pyproject property file defines all of the build settings for each
+project, with some projects overriding certain specific values. The GUI
+doesn't always reflect the correct settings and may confuse the user
+with false information, especially for settings that automatically adapt
+for diffirent configurations.
+
+
+Your Own Extension DLLs
 -----------------------
 
-If you want to create your own extension module DLL, there's an example
-with easy-to-follow instructions in ../PC/example/; read the file
-readme.txt there first.
+If you want to create your own extension module DLL (.pyd), there's an
+example with easy-to-follow instructions in ..\PC\example_nt\; read the
+file readme.txt there first.