Provide forward compatible cmake paradigms

Automatically extract version information
from the zstd.h file.  Use naming of variables
consisent with modern cmake and https://semver.org/
(Semantic Versioning 2.0.0, MAJOR, MINOR, PATCH)

Modern versions of cmake provide consistent
paradigms for configuring project external
interface values.

This set of changes provide a back port of
some of cmake 3+ paradigms back to cmake 2.8.9.
Set and allow use of the current cmake policies
for newer versions of cmake when available to
allow for modern compiler features to be
utilized when available.

NOTE: The intent is that future modifications to
cmake will enable (conditional on cmake version support)
the ability to support modern linkage, and target
export mechanisms.  Those future changes will
make incorporating zstd into other packages
much easier.

This patch also allows the more rigourous error
checking of commmon cmake errors to be preformed
by cmake (i.e. more stringent syntax checking and
create errors for common hard to find misuses of
cmake variables).

This patch also provides support for modern
compiler support options by cmake (like
enabling interprocedural optimization
if link time optimizations are known to be supported
by the compiler envirionment.  IPO can be supported
by setting the CMAKE_INTERPROCEDURAL_OPTIMIZATION variable
for newer versions of cmake.

build/cmake/CMakeLists.txt

@@ -7,10 +7,48 @@
 # in the COPYING file in the root directory of this source tree).
 # ################################################################
 
-cmake_minimum_required(VERSION 2.8.9)
+cmake_minimum_required(VERSION 2.8.9 FATAL_ERROR)
+  
+# As of 2018-12-26 ZSTD has been validated to build with cmake version 3.13.2 new policies. 
+# Set and use the newest cmake policies that are validated to work 
+set(ZSTD_MAX_VALIDATED_CMAKE_VERSION "3.13.2") 
+if("${CMAKE_MAJOR_VERSION}" LESS 3) # Cmake version 2 does not understand the VERSION_LESS_EQUAL operator
+  set(ZSTD_CMAKE_POLICY_VERSION "${CMAKE_VERSION}") 
+else()
+  if("${CMAKE_VERSION}" VERSION_LESS_EQUAL "${ZSTD_MAX_VALIDATED_CMAKE_VERSION}") 
+    set(ZSTD_CMAKE_POLICY_VERSION "${CMAKE_VERSION}") 
+  else() 
+    set(ZSTD_CMAKE_POLICY_VERSION "${ZSTD_MAX_VALIDATED_CMAKE_VERSION}") 
+  endif() 
+endif()
+cmake_policy(VERSION ${ZSTD_CMAKE_POLICY_VERSION})
 
-project(zstd)
+list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/CMakeModules")
 set(ZSTD_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../..")
+set(LIBRARY_DIR ${ZSTD_SOURCE_DIR}/lib)
+# Parse version
+include(GetZstdLibraryVersion)
+GetZstdLibraryVersion(${LIBRARY_DIR}/zstd.h zstd_VERSION_MAJOR zstd_VERSION_MINOR zstd_VERSION_PATCH)
+
+if( CMAKE_MAJOR_VERSION LESS 3 )
+  ## Provide cmake 3+ behavior for older versions of cmake
+  project(zstd)
+  set(PROJECT_VERSION_MAJOR ${zstd_VERSION_MAJOR})
+  set(PROJECT_VERSION_MINOR ${zstd_VERSION_MINOR})
+  set(PROJECT_VERSION_PATCH ${zstd_VERSION_PATCH})
+  set(PROJECT_VERSION "${zstd_VERSION_MAJOR}.${zstd_VERSION_MINOR}.${zstd_VERSION_PATCH}")
+  enable_language(C)   # Main library is in C
+  enable_language(CXX) # Testing contributed code also utilizes CXX
+else()
+  project(zstd
+    VERSION "${zstd_VERSION_MAJOR}.${zstd_VERSION_MINOR}.${zstd_VERSION_PATCH}"
+    LANGUAGES C   # Main library is in C
+              CXX # Testing contributed code also utilizes CXX
+    )
+endif()
+message(STATUS "ZSTD VERSION: ${zstd_VERSION}")
+set(zstd_HOMEPAGE_URL "http://www.zstd.net")
+set(zstd_DESCRIPTION  "Zstandard is a real-time compression algorithm, providing high compression ratios.")
 
 # Set a default build type if none was specified
 if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
@@ -20,7 +58,6 @@ if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
   set_property(CACHE CMAKE_BUILD_TYPE PROPERTY STRINGS "Debug" "Release" "MinSizeRel" "RelWithDebInfo")
 endif()
 
-list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/CMakeModules")
 include(GNUInstallDirs)
 
 #-----------------------------------------------------------------------------

build/cmake/CMakeModules/GetZstdLibraryVersion.cmake

@@ -1,9 +1,10 @@
-function(GetZstdLibraryVersion _header _major _minor _release)
+function(GetZstdLibraryVersion _header _major _minor _patch)
     # Read file content
     file(READ ${_header} CONTENT)
 
     string(REGEX MATCH ".*define ZSTD_VERSION_MAJOR *([0-9]+).*define ZSTD_VERSION_MINOR *([0-9]+).*define ZSTD_VERSION_RELEASE *([0-9]+)" VERSION_REGEX "${CONTENT}")
     set(${_major} ${CMAKE_MATCH_1} PARENT_SCOPE)
     set(${_minor} ${CMAKE_MATCH_2} PARENT_SCOPE)
-    set(${_release} ${CMAKE_MATCH_3} PARENT_SCOPE)
+    set(${_patch} ${CMAKE_MATCH_3} PARENT_SCOPE)
 endfunction()
+

build/cmake/lib/CMakeLists.txt

@@ -18,14 +18,8 @@ if(NOT ZSTD_BUILD_SHARED AND NOT ZSTD_BUILD_STATIC)
 endif()
 
 # Define library directory, where sources and header files are located
-set(LIBRARY_DIR ${ZSTD_SOURCE_DIR}/lib)
 include_directories(${LIBRARY_DIR} ${LIBRARY_DIR}/common)
 
-# Parse version
-include(GetZstdLibraryVersion)
-GetZstdLibraryVersion(${LIBRARY_DIR}/zstd.h LIBVER_MAJOR LIBVER_MINOR LIBVER_RELEASE)
-message(STATUS "ZSTD VERSION ${LIBVER_MAJOR}.${LIBVER_MINOR}.${LIBVER_RELEASE}")
-
 set(Sources
         ${LIBRARY_DIR}/common/entropy_common.c
         ${LIBRARY_DIR}/common/fse_decompress.c
@@ -155,7 +149,7 @@ if (ZSTD_BUILD_SHARED)
             libzstd_shared
             PROPERTIES
             OUTPUT_NAME zstd
-            SOVERSION ${LIBVER_MAJOR}.${LIBVER_MINOR}.${LIBVER_RELEASE})
+            SOVERSION ${zstd_VERSION_MAJOR}.${zstd_VERSION_MINOR}.${zstd_VERSION_PATCH})
 endif ()
 
 if (ZSTD_BUILD_STATIC)
@@ -170,7 +164,7 @@ if (UNIX)
     set(PREFIX "${CMAKE_INSTALL_PREFIX}")
     set(LIBDIR "${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}")
     set(INCLUDEDIR "${CMAKE_INSTALL_PREFIX}/include")
-    set(VERSION "${LIBVER_MAJOR}.${LIBVER_MINOR}.${LIBVER_RELEASE}")
+    set(VERSION "${zstd_VERSION_MAJOR}.${zstd_VERSION_MINOR}.${zstd_VERSION_PATCH}")
     add_custom_target(libzstd.pc ALL
             ${CMAKE_COMMAND} -DIN="${LIBRARY_DIR}/libzstd.pc.in" -DOUT="libzstd.pc"
             -DPREFIX="${PREFIX}" -DLIBDIR="${LIBDIR}" -DINCLUDEDIR="${INCLUDEDIR}" -DVERSION="${VERSION}"