Set "compatibility version" and "current version".

For #304.

Change-Id: I74e2720ecad9a0b22e8cd73dbffe2e02599827c5
Reviewed-on: https://code-review.googlesource.com/c/re2/+/58450
Reviewed-by: Paul Wankadia <[email protected]>

CMakeLists.txt

@@ -25,6 +25,10 @@ option(USEPCRE "use PCRE in tests and benchmarks" OFF)
 # so we provide an option similar to BUILD_TESTING, but just for RE2.
 option(RE2_BUILD_TESTING "enable testing for RE2" ON)
 
+# ABI version
+# http://tldp.org/HOWTO/Program-Library-HOWTO/shared-libraries.html
+set(SONAME 9)
+
 set(EXTRA_TARGET_LINK_LIBRARIES)
 
 if(CMAKE_CXX_COMPILER_ID MATCHES "MSVC")
@@ -82,7 +86,8 @@ set(RE2_SOURCES
     )
 
 add_library(re2 ${RE2_SOURCES})
-target_include_directories (re2 PUBLIC $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>)
+target_include_directories(re2 PUBLIC $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>)
+set_target_properties(re2 PROPERTIES SOVERSION ${SONAME} VERSION ${SONAME}.0.0)
 add_library(re2::re2 ALIAS re2)
 
 if(RE2_BUILD_TESTING)

Makefile

@@ -55,7 +55,7 @@ ifeq ($(shell uname),Darwin)
 SOEXT=dylib
 SOEXTVER=$(SONAME).$(SOEXT)
 SOEXTVER00=$(SONAME).0.0.$(SOEXT)
-MAKE_SHARED_LIBRARY=$(CXX) -dynamiclib -Wl,-install_name,$(libdir)/libre2.$(SOEXTVER),-exported_symbols_list,libre2.symbols.darwin $(RE2_LDFLAGS) $(LDFLAGS)
+MAKE_SHARED_LIBRARY=$(CXX) -dynamiclib -Wl,-compatibility_version,$(SONAME),-current_version,$(SONAME).0.0,-install_name,$(libdir)/libre2.$(SOEXTVER),-exported_symbols_list,libre2.symbols.darwin $(RE2_LDFLAGS) $(LDFLAGS)
 else ifeq ($(shell uname),SunOS)
 SOEXT=so
 SOEXTVER=$(SOEXT).$(SONAME)