create cmake project structure and c++ test app

CMakeLists.txt

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+cmake_minimum_required(VERSION 3.12)
+
+project(doompanning)
+
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+
+## Create binaries in the root of the build directory
+set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR})
+set(CMAKE_VERBOSE_MAKEFILE ON)
+
+add_subdirectory(external)
+add_subdirectory(src)

external/CMakeLists.txt

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+option(NNG_SETSTACKSIZE "Use rlimit for thread stack size" ON)
+set(NNG_TESTS OFF)
+set(NNG_ENABLE_NNGCAT OFF)
+add_subdirectory(nng)
+
+option(SPDLOG_FMT_EXTERNAL "Use external fmt library instead of bundled" OFF)
+option(SPDLOG_INSTALL "Generate the install target" ON)
+add_subdirectory(spdlog)

src/CMakeLists.txt

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+find_package(nng CONFIG REQUIRED)
+find_package(Threads)
+add_executable(doompanning doompanning.cc)
+target_link_libraries(doompanning
+    PRIVATE nng::nng
+    PRIVATE spdlog::spdlog
+    )
+target_compile_features(doompanning PRIVATE cxx_std_17)

src/doompanning.cc

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+#include <cstdlib>
+#include <nng/nng.h>
+#include <nng/protocol/pubsub0/pub.h>
+#include <nng/protocol/pubsub0/sub.h>
+#include <spdlog/spdlog.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+void dp_nng_fatal(const std::string &msg, int rv)
+{
+    spdlog::error("{}: {}", msg, nng_strerror(rv));
+    abort();
+}
+
+void dp_errno_fatal(const std::string &msg)
+{
+    spdlog::error("{}: {}", msg, strerror(errno));
+    abort();
+}
+
+nng_socket make_ctrl_pub(const char *url)
+{
+    nng_socket sock;
+
+    if (auto res = nng_pub0_open(&sock))
+        dp_nng_fatal("make_ctrl_pub/nng_pub0_open", res);
+
+    if (auto res = nng_listen(sock, url, nullptr, 0))
+        dp_nng_fatal("make_ctrl_pub/nng_listen", res);
+
+    return sock;
+}
+
+nng_socket make_ctrl_sub(const char *url)
+{
+    nng_socket sock;
+
+    if (auto res = nng_sub0_open(&sock))
+        dp_nng_fatal("make_ctrl_pub/nng_sub0_open", res);
+
+    if (auto res = nng_listen(sock, url, nullptr, 0))
+        dp_nng_fatal("make_ctrl_sub/nng_listen", res);
+
+    return sock;
+}
+
+nng_socket make_doom_pub(const char *url)
+{
+}
+
+nng_socket make_doom_sub(const char *url)
+{
+}
+
+static const char *CtrlUrl = "ipc://666_ctrl.socket";
+static const char *DoomUrl = "ipc://666_doom.socket";
+static const size_t NumDooms = 2;
+
+int run_doom(size_t id)
+{
+    spdlog::debug("doom#{} running", id);
+    return 0;
+}
+
+int main(int argc, char *argv[])
+{
+    spdlog::set_level(spdlog::level::debug);
+    spdlog::set_pattern("[%H:%M:%S.%e] [pid=%P] [%^%l%$] %v");
+    spdlog::info("Hello, doomed world!");
+
+    for (size_t i=0; i<NumDooms; ++i)
+    {
+        auto res = fork();
+
+        if (res == -1)
+            dp_errno_fatal("spawn doom");
+        else if (res == 0)
+            return run_doom(i);
+        else
+            spdlog::debug("spawned doom#{}", i);
+    }
+
+    return 0;
+
+    auto ctrlPubSock = make_ctrl_pub(CtrlUrl);
+    auto ctrlSubSock = make_ctrl_sub(DoomUrl);
+
+    if (auto res = nng_send(ctrlPubSock, (void *)"foobar", 7, 0))
+        dp_nng_fatal("ctrl send", res);
+
+
+    nng_close(ctrlPubSock);
+    nng_close(ctrlSubSock);
+    return 0;
+}