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.

4 files changed, 80 insertions, 8 deletions

diff --git a/.circleci/build-and-test.sh b/.circleci/build-and-test.sh
index 068f0f91..c4fb8eaa 100755
--- a/.circleci/build-and-test.sh
+++ b/.circleci/build-and-test.sh
@@ -4,12 +4,12 @@
 # common build & test steps for CircleCI jobs
 #
 
-uname -a
 cmake --version
 ninja --version
 
 mkdir build
 cd build
-cmake -G Ninja -DCMAKE_BUILD_TYPE=${BUILD_TYPE:-Debug} -DNNG_ENABLE_COVERAGE=${COVERAGE:-OFF} ..
+cmake -G Ninja -DCMAKE_BUILD_TYPE=${BUILD_TYPE:-Debug} -DNNG_ENABLE_COVERAGE=${COVERAGE:-OFF} -DBUILD_SHARED_LIBS=${SHARED_LIBS:=ON} ..
 ninja
+ninja install
 env CTEST_OUTPUT_ON_FAILURE=1 ninja test
diff --git a/.circleci/build-demos.sh b/.circleci/build-demos.sh
new file mode 100755
index 00000000..488c142d
--- /dev/null
+++ b/.circleci/build-demos.sh
@@ -0,0 +1,13 @@
+#!/bin/bash
+
+#
+# build the demos to make sure they all build cleanly
+#
+
+for dir in demo/*; do
+	demo=$(basename $dir)
+	mkdir build-demo-${demo}
+	( cd build-demo-${demo} &&
+	cmake -G Ninja ../demo/${demo} &&
+	ninja ) || exit 1
+done
diff --git a/.circleci/config.yml b/.circleci/config.yml
index efe64900..2a3711f7 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -22,7 +22,6 @@ jobs:
       - run: >
           apt-get install -y --allow-unauthenticated
           build-essential
-          curl
           asciidoctor
           cmake
           libmbedtls-dev
@@ -32,6 +31,52 @@ jobs:
       - run: ./etc/format-check.sh
       - run: ./.circleci/build-and-test.sh
 
+  "gcc - static":
+    docker:
+      - image: ubuntu:16.04
+        environment:
+          CC: gcc
+          CXX: g++
+          SHARED_LIBS: OFF
+          CTEST_OUTPUT_ON_FAILURE: 1
+    steps:
+      - checkout
+      - run: apt-get update -qq
+      - run: apt-get install -y software-properties-common
+      - run: add-apt-repository ppa:ubuntu-toolchain-r/test
+      - run: apt-get update -qq
+      - run: >
+          apt-get install -y --allow-unauthenticated
+          build-essential
+          cmake
+          libmbedtls-dev
+          ninja-build
+      - run: ./.circleci/build-and-test.sh
+
+  "gcc - demos":
+    docker:
+      - image: ubuntu:16.04
+        environment:
+          CC: gcc
+          CXX: g++
+          CTEST_OUTPUT_ON_FAILURE: 1
+    steps:
+      - checkout
+      - run: apt-get update -qq
+      - run: apt-get install -y software-properties-common
+      - run: add-apt-repository ppa:ubuntu-toolchain-r/test
+      - run: apt-get update -qq
+      - run: >
+          apt-get install -y --allow-unauthenticated
+          build-essential
+          cmake
+          libmbedtls-dev
+          ninja-build
+      - run: ./.circleci/run-cmake.sh
+      - run: ninja -C build
+      - run: ninja -C build install
+      - run: ./.circleci/build-demos.sh
+
   "gcc - build, test, coverage":
     docker:
       - image: ubuntu:16.04
@@ -40,6 +85,7 @@ jobs:
           CXX: g++-8
           COVERAGE: "ON"
           GCOV: gcov-8
+          CTEST_OUTPUT_ON_FAILURE: 1
     steps:
       - checkout
       - run: apt-get update -qq
@@ -64,11 +110,13 @@ workflows:
   build_and_test:
     jobs:
       - "clang - build, test"
+      - "gcc - static"
       - "gcc - build, test, coverage"
+      - "gcc - demos"
 
-notify:
-  webhooks:
-    # A list of hook hashes, containing the url field
-    # gitter hook
-    - url: ${GITTER_WEBHOOK}
+#notify:
+#  webhooks:
+#    # A list of hook hashes, containing the url field
+#    # gitter hook
+#    - url: ${GITTER_WEBHOOK}
 
diff --git a/.circleci/run-cmake.sh b/.circleci/run-cmake.sh
new file mode 100755
index 00000000..ca0caaa4
--- /dev/null
+++ b/.circleci/run-cmake.sh
@@ -0,0 +1,11 @@
+#!/bin/bash
+
+#
+# common build & test steps for CircleCI jobs
+#
+cmake --version
+ninja --version
+
+mkdir build
+cd build
+cmake -G Ninja -DCMAKE_BUILD_TYPE=${BUILD_TYPE:-Debug} -DNNG_ENABLE_COVERAGE=${COVERAGE:-OFF} -DBUILD_SHARED_LIBS=${SHARED_LIBS:=ON} ..