fixes #486 Revisit SOVERSION and VERSION

fixes #485 Honor BUILD_SHARED_LIBS
fixes #483 Don't expose private symbols in shared library
fixes #481 Export CMake target

This is a "large" commit involving changes that don't affect the
code directly, but which have an impact on how we package and build
our project.

The most significant of these changes is that we now build only
either a shared or a static library, depending on the setting of
the BUILD_SHARED_LIBS option.  We also suppress private symbols
from being exposed when the underlying toolchain lets us do so.

Minor updates to the way we version the ABI are used, and we now
have a nice exported CMake project.

To import this project in another, simply do find_package(nng)
and you can add target_link_libraries(nng::nng) to your targets.
CMake does the rest for you.

1 files changed, 22 insertions, 0 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index ee50ce0d..60b1726c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -33,6 +33,7 @@ include (CheckSymbolExists)
 include (CheckStructHasMember)
 include (CheckLibraryExists)
 include (CheckCSourceCompiles)
+include (CheckCCompilerFlag)
 include (CMakeDependentOption)
 include (GNUInstallDirs)
 include (TestBigEndian)
@@ -55,6 +56,7 @@ set (NNG_DESCRIPTION "High-Performance Scalability Protocols NextGen")
 set (ISSUE_REPORT_MSG "Please consider opening an issue at https://github.com/nanomsg/nng")
 
 # Determine library versions.
+set (NNG_ABI_SOVERSION 1)
 set (NNG_ABI_VERSION "1.0.0")
 
 # Determine package version.
@@ -86,6 +88,8 @@ endif()
 
 # User-defined options.
 
+option(BUILD_SHARED_LIBS "Build shared library" ${BUILD_SHARED_LIBS})
+
 option (NNG_TESTS "Build and run tests" ON)
 option (NNG_TOOLS "Build extra tools" ON)
 option (NNG_ENABLE_NNGCAT "Enable building nngcat utility." ${NNG_TOOLS})
@@ -267,6 +271,14 @@ else()
     add_definitions (-DNNG_LITTLE_ENDIAN)
 endif()
 
+# If the compiler is not on Windows, does it support hiding the
+# symbols by default?  For shared libraries we would like to do this.
+if (NOT WIN32 AND NOT CYGWIN)
+    check_c_compiler_flag(-fvisibility=hidden NNG_HIDDEN_VISIBILITY)
+    if (NNG_HIDDEN_VISIBILITY)
+        add_definitions (-DNNG_HIDDEN_VISIBILITY)
+    endif()
+endif()
 
 find_package (Threads REQUIRED)
 
@@ -408,6 +420,16 @@ nng_check_sym (strnlen string.h NNG_HAVE_STRNLEN)
 nng_check_sym (strcasecmp string.h NNG_HAVE_STRCASECMP)
 nng_check_sym (strncasecmp string.h NNG_HAVE_STRNCASECMP)
 
+# Set a static symbol.  We do this for testing, so that tests can
+# be skipped if they would rely on symbols that might not be exported.
+# For example, idhash depends on private symbols, so don't test it
+# when using a shared library on Windows because the symbols won't
+# resolve.
+if (NOT(BUILD_SHARED_LIBS))
+    set (NNG_STATIC_LIB ON)
+    message(STATUS "Building static libs")
+endif()
+
 add_subdirectory (src)
 
 if (NNG_TESTS)