intermittent ctrl commit: fork() based spawn code which makes nng panic

src/doompanning.cc

@@ -15,6 +15,7 @@
 #include <signal.h>
 #include <spawn.h>
 #include <sys/wait.h>
+#include <unistd.h>
 
 #include "dp_common.h"
 #include "dp_util.hpp"
@@ -56,7 +57,7 @@ struct ControllerActions
 
 #define DOOM_EXECUTABLE "dp_doom"
 
-void spawn_doom(ControllerContext &ctx)
+void spawn_doom_posix_spawn(ControllerContext &ctx)
 {
     DoomState ds;
 
@@ -64,7 +65,8 @@ void spawn_doom(ControllerContext &ctx)
 
     // TODO: Close stdin and stdout? Leave them open for now to see the logging
     // output.
-    // FIXME: this doesn't work with SDL :(
+    // FIXME: SDL is not able to init its sound system in the doomchild. Try to ask
+    // it if it's already initialized and skip if true.
     if (auto err = posix_spawn(&ds.id, DOOM_EXECUTABLE, nullptr, nullptr,
         const_cast<char *const *>(argv), nullptr))
     {
@@ -82,6 +84,45 @@ void spawn_doom(ControllerContext &ctx)
     ctx.dooms.emplace_back(ds);
 }
 
+// nng does not like this at all and panics (for good reasons)
+void spawn_doom_fork(ControllerContext &ctx)
+{
+    auto pid = fork();
+
+    if (pid < 0)
+    {
+        log_error("Could not spawn doom: %s", strerror(errno));
+        return;
+    }
+
+    if (pid == 0)       // doomchild
+    {
+        log_info("doomchild %d cleaning the room", getpid());
+        ImGui::DestroyContext();
+        log_info("doomchild %d cleanup done", getpid());
+
+        const char *const argv[] = { DOOM_EXECUTABLE, nullptr };
+        execvp(DOOM_EXECUTABLE, const_cast<char *const *>(argv));
+    }
+    else if (pid > 0)   // doomparent
+    {
+        DoomState ds;
+        ds.id = pid;
+        ds.texture = SDL_CreateTexture(ctx.renderer, SDL_PIXELFORMAT_RGB888,
+            SDL_TEXTUREACCESS_STREAMING, DoomScreenWidth, DoomScreenHeight);
+        if (!ds.texture)
+            dp_sdl_fatal("SDL_CreateTexture");
+
+        log_info("Spawned new doom, pid=%d", ds.id);
+        ctx.dooms.emplace_back(ds);
+    }
+}
+
+inline void spawn_doom(ControllerContext &ctx)
+{
+    spawn_doom_posix_spawn(ctx);
+}
+
 void end_all_dooms(ControllerContext &ctx)
 {
     nng_msg *msg = nullptr;