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.

13 files changed, 174 insertions, 20 deletions

diff --git a/demo/async/CMakeLists.txt b/demo/async/CMakeLists.txt
new file mode 100644
index 00000000..614bcfc3
--- /dev/null
+++ b/demo/async/CMakeLists.txt
@@ -0,0 +1,24 @@
+#
+# Copyright 2018 Capitar IT Group BV <info@capitar.com>
+# Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
+#
+# This software is supplied under the terms of the MIT License, a
+# copy of which should be located in the distribution where this
+# file was obtained (LICENSE.txt).  A copy of the license may also be
+# found online at https://opensource.org/licenses/MIT.
+
+cmake_minimum_required (VERSION 2.8.7)
+
+project(nng-asyncdemo)
+
+set(PARALLEL 128 CACHE STRING "Parallelism (min 4, max 1000)")
+
+# Call this from your own project's makefile.
+find_package(nng CONFIG REQUIRED)
+
+add_executable(server server.c)
+target_link_libraries(server nng::nng)
+target_compile_definitions(server PRIVATE -DPARALLEL=${PARALLEL})
+
+add_executable(client client.c)
+target_link_libraries(client nng::nng)
diff --git a/demo/async/README.adoc b/demo/async/README.adoc
index ec91c722..87c44cec 100644
--- a/demo/async/README.adoc
+++ b/demo/async/README.adoc
@@ -6,8 +6,11 @@ processing with minimal fuss.
 
 == Compiling
 
-You can override the level of concurrency with the `PARALLEL`
-define.  This determines how many requests the server will accept
+This is set up for configuration with CMake for ease of use.
+
+You can override the level of concurrency with the `PARALLEL` option.
+
+This determines how many requests the server will accept
 at a time, and keep outstanding.  Note that for our toy implementation,
 we create this many "logical" flows of execution (contexts) (these are
 _NOT_ threads), where a request is followed by a reply.
@@ -20,6 +23,8 @@ you can't have more than one client per descriptor.  Contexts can be used
 on the client side to support many thousands of concurrent requests over
 even just a single TCP connection, however.)
 
+You can also build this all by hand with Make or whatever.
+
 On UNIX-style systems:
 
 [source, bash]
diff --git a/demo/http_client/CMakeLists.txt b/demo/http_client/CMakeLists.txt
new file mode 100644
index 00000000..3fe126f9
--- /dev/null
+++ b/demo/http_client/CMakeLists.txt
@@ -0,0 +1,18 @@
+#
+# Copyright 2018 Capitar IT Group BV <info@capitar.com>
+# Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
+#
+# This software is supplied under the terms of the MIT License, a
+# copy of which should be located in the distribution where this
+# file was obtained (LICENSE.txt).  A copy of the license may also be
+# found online at https://opensource.org/licenses/MIT.
+
+cmake_minimum_required (VERSION 2.8.7)
+
+project(http_client)
+
+# Call this from your own project's makefile.
+find_package(nng CONFIG REQUIRED)
+
+add_executable(http_client http_client.c)
+target_link_libraries(http_client nng::nng)
diff --git a/demo/http_client/README.adoc b/demo/http_client/README.adoc
index a0fb54e4..f8777557 100644
--- a/demo/http_client/README.adoc
+++ b/demo/http_client/README.adoc
@@ -30,6 +30,17 @@ Linux and macOS:
 % ${CC} ${CPPFLAGS} http_client.c -o http_client ${LDFLAGS}
 ----
 
+Alternatively, CMake can be used.  Here's an example if you have
+Ninja build handy (highly recommended):
+
+[source, bash]
+----
+% mkdir build
+% cd build
+% cmake -G Ninja  ..
+% ninja
+----
+
 == Running
 
 Make sure you specify the full URL (if the root page include
@@ -39,4 +50,3 @@ the simple "/".  The URL parser does not add it for you automatically.)
 ----
 % ./http_client http://httpbin.org/ip
 ----
-
diff --git a/demo/http_client/http_client.c b/demo/http_client/http_client.c
index 522c1cd1..a00c842f 100644
--- a/demo/http_client/http_client.c
+++ b/demo/http_client/http_client.c
@@ -34,6 +34,7 @@
 //
 
 #include <nng/nng.h>
+#include <nng/supplemental/http/http.h>
 #include <stdio.h>
 #include <stdlib.h>
 
diff --git a/demo/raw/CMakeLists.txt b/demo/raw/CMakeLists.txt
new file mode 100644
index 00000000..15e481d5
--- /dev/null
+++ b/demo/raw/CMakeLists.txt
@@ -0,0 +1,20 @@
+#
+# Copyright 2018 Capitar IT Group BV <info@capitar.com>
+# Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
+#
+# This software is supplied under the terms of the MIT License, a
+# copy of which should be located in the distribution where this
+# file was obtained (LICENSE.txt).  A copy of the license may also be
+# found online at https://opensource.org/licenses/MIT.
+
+cmake_minimum_required (VERSION 2.8.7)
+
+project(raw)
+
+set(PARALLEL 128 CACHE STRING "Parallelism (min 4, max 1000)")
+
+find_package(nng CONFIG REQUIRED)
+
+add_executable(raw raw.c)
+target_link_libraries(raw nng::nng)
+target_compile_definitions(raw PRIVATE -DPARALLEL=${PARALLEL})
diff --git a/demo/raw/README.adoc b/demo/raw/README.adoc
index 35290616..2190dc49 100644
--- a/demo/raw/README.adoc
+++ b/demo/raw/README.adoc
@@ -1,14 +1,15 @@
-= async
+= raw
 
 This is a simple asynchronous demo, that demonstrates use of the RAW
-option with a server, along with async message handling, to obtain a
+sockets with a server, along with async message handling, to obtain a
 very high level of asynchronous operation, suitable for use in a highly
 concurrent server application.
 
 == Compiling
 
-You can override the level of concurrency with the `PARALLEL`
-define.  This determines how many requests the server will accept
+You can override the level of concurrency with the `PARALLEL` option.
+
+This determines how many requests the server will accept
 at a time, and keep outstanding.  Note that for our toy
 implementation, we create this many "logical" flows of execution
 (these are _NOT_ threads), where a request is followed by a reply.
@@ -16,14 +17,24 @@ implementation, we create this many "logical" flows of execution
 The value of `PARALLEL` must be at least one, and may be as large
 as your memory will permit.  (The default value is 32.)
 
-On UNIX-style systems:
+The best way to build is using cmake and Ninja build:
+
+[source, bash]
+----
+% mkdir build
+% cd build
+% cmake -G Ninja ..
+% ninja
+----
+
+You can also build the hard way.  For example, on UNIX-style systems:
 
 [source, bash]
 ----
 % export CPPFLAGS="-D PARALLEL=32 -I /usr/local/include"
 % export LDFLAGS="-L /usr/local/lib -lnng"
 % export CC="cc"
-% ${CC} ${CPPFLAGS} async.c -o async ${LDFLAGS}
+% ${CC} ${CPPFLAGS} raw.c -o raw ${LDFLAGS}
 ----
 
 == Running
@@ -42,12 +53,12 @@ In the following example, all of the clients should complete within
 ----
 % export URL="tcp://127.0.0.1:55995"
 # start the server
-% ./async $URL -s &
+% ./raw $URL -s &
 # start a bunch of clients
 # Note that these all run concurrently!
-% ./async $URL 2 &
-% ./async $URL 2 &
-% ./async $URL 2 &
-% ./async $URL 2 &
-% ./async $URL 2 &
+% ./raw $URL 2 &
+% ./raw $URL 2 &
+% ./raw $URL 2 &
+% ./raw $URL 2 &
+% ./raw $URL 2 &
 ----
diff --git a/demo/raw/async.c b/demo/raw/raw.c
index 0285d8d2..0285d8d2 100644
--- a/demo/raw/async.c
+++ b/demo/raw/raw.c
diff --git a/demo/reqrep/CMakeLists.txt b/demo/reqrep/CMakeLists.txt
new file mode 100644
index 00000000..d6982446
--- /dev/null
+++ b/demo/reqrep/CMakeLists.txt
@@ -0,0 +1,17 @@
+#
+# Copyright 2018 Capitar IT Group BV <info@capitar.com>
+# Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
+#
+# This software is supplied under the terms of the MIT License, a
+# copy of which should be located in the distribution where this
+# file was obtained (LICENSE.txt).  A copy of the license may also be
+# found online at https://opensource.org/licenses/MIT.
+
+cmake_minimum_required (VERSION 2.8.7)
+
+project(reqrep)
+
+find_package(nng CONFIG REQUIRED)
+
+add_executable(reqrep reqrep.c)
+target_link_libraries(reqrep nng::nng)
diff --git a/demo/reqrep/README.adoc b/demo/reqrep/README.adoc
index b66d694c..5bc3d043 100644
--- a/demo/reqrep/README.adoc
+++ b/demo/reqrep/README.adoc
@@ -19,8 +19,19 @@ compiled on 64-bit systems.)
 
 == Compiling
 
-The following is an example typical of UNIX and similar systems like
-Linux and macOS:
+CMake with ninja-build is simplest:
+
+[source, bash]
+----
+% mkdir build
+% cd build
+% cmake -G Ninja ..
+% ninja
+----
+
+Or if you prefer a traditional approach, 
+the following is an example typical of UNIX and similar systems like
+Linux and macOS may appeal:
 
 [source, bash]
 ----
diff --git a/demo/rest/CMakeLists.txt b/demo/rest/CMakeLists.txt
new file mode 100644
index 00000000..5466e3c7
--- /dev/null
+++ b/demo/rest/CMakeLists.txt
@@ -0,0 +1,17 @@
+#
+# Copyright 2018 Capitar IT Group BV <info@capitar.com>
+# Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
+#
+# This software is supplied under the terms of the MIT License, a
+# copy of which should be located in the distribution where this
+# file was obtained (LICENSE.txt).  A copy of the license may also be
+# found online at https://opensource.org/licenses/MIT.
+
+cmake_minimum_required (VERSION 2.8.7)
+
+project(rest)
+
+find_package(nng CONFIG REQUIRED)
+
+add_executable(rest-server server.c)
+target_link_libraries(rest-server nng::nng)
diff --git a/demo/rest/README.adoc b/demo/rest/README.adoc
index 6a363329..df3e30b0 100644
--- a/demo/rest/README.adoc
+++ b/demo/rest/README.adoc
@@ -3,7 +3,7 @@
 This is a somewhat contrived demonstration, but may be useful
 in a pattern for solving real world problems.
 
-There is a single "server" program, that does these:
+There is a single "server" (rest-server) program, that does these:
 
 . REST API at /api/rest/rot13 - this API takes data from HTTP POST commands,
   and forwards them to an NNG REQ socket.  When the REQ response comes,
@@ -17,9 +17,29 @@ There is a single "server" program, that does these:
 [source, bash]
 ----
 % env PORT=8888  # default
-% ./server &
+% ./rest-server &
 % curl -d ABC http://127.0.0.1:8888/api/rest/rot13; echo
 NOP
 % curl -d ABC http://127.0.0.1:8888/api/rest/rot13; echo
 ABC
 ----
+
+== Compiling
+
+To build the program, we recommend CMake and Ninja-Build.
+
+[source, bash]
+----
+% mkdir build
+% cd build
+% cmake -G Ninja ..
+% ninja
+----
+
+Alternatively, you can go old-school.
+Here's the simplest option for Linux:
+
+[source, bash]
+----
+% cc server.c -o rest-server -I /usr/local/include -lnng
+----
diff --git a/demo/rest/server.c b/demo/rest/server.c
index 788fc8f1..72c24cb1 100644
--- a/demo/rest/server.c
+++ b/demo/rest/server.c
@@ -98,7 +98,7 @@ rest_free_job(rest_job *job)
 	if (job->msg != NULL) {
 		nng_msg_free(job->msg);
 	}
-	if (job->ctx != 0) {
+	if (nng_ctx_id(job->ctx) != 0) {
 		nng_ctx_close(job->ctx);
 	}
 	free(job);