Implement IPC API and Posix implementation

CMakeLists.txt

@@ -4000,6 +4000,9 @@ if(SDL_SHARED)
   if(NOT CMAKE_VERSION VERSION_LESS "3.16")
     target_precompile_headers(SDL3-shared PRIVATE "$<$<OR:$<COMPILE_LANGUAGE:C>,$<COMPILE_LANGUAGE:CXX>>:${PROJECT_SOURCE_DIR}/src/SDL_internal.h>")
   endif()
+  if(HAIKU)
+    target_link_libraries(SDL3-shared PUBLIC network)
+  endif()
 endif()
 
 if(SDL_STATIC)
@@ -4024,6 +4027,9 @@ if(SDL_STATIC)
   if(NOT CMAKE_VERSION VERSION_LESS "3.16")
     target_precompile_headers(SDL3-static PRIVATE "$<$<OR:$<COMPILE_LANGUAGE:C>,$<COMPILE_LANGUAGE:CXX>>:${PROJECT_SOURCE_DIR}/src/SDL_internal.h>")
   endif()
+  if(HAIKU)
+    target_link_libraries(SDL3-static PUBLIC network)
+  endif()
 endif()
 
 sdl_compile_definitions(
@@ -4055,6 +4061,9 @@ if(SDL_TEST_LIBRARY)
   target_link_libraries(SDL3_test PRIVATE ${EXTRA_TEST_LIBS})
   set_property(TARGET SDL3_test APPEND PROPERTY COMPATIBLE_INTERFACE_STRING "SDL_VERSION")
   set_property(TARGET SDL3_test PROPERTY INTERFACE_SDL_VERSION "SDL${SDL3_VERSION_MAJOR}")
+  if(HAIKU)
+    target_link_libraries(SDL3_test PUBLIC network)
+  endif()
 endif()
 
 ##### Configure installation folders #####

include/SDL3/SDL_process.h

@@ -63,6 +63,11 @@ extern "C" {
  */
 typedef struct SDL_Process SDL_Process;
 
+/**
+ * An opaque handle representing an IPC channel.
+ */
+typedef struct SDL_IPC SDL_IPC;
+
 /**
  * Create a new process.
  *
@@ -201,6 +206,8 @@ typedef enum SDL_ProcessIO
  *   property is only important if you want to start programs that does
  *   non-standard command-line processing, and in most cases using
  *   `SDL_PROP_PROCESS_CREATE_ARGS_POINTER` is sufficient.
+ * - `SDL_PROP_PROCESS_CREATE_SDL_IPC`: true if the process should create an
+ *   IPC channel for sharing resources.
  *
  * On POSIX platforms, wait() and waitpid(-1, ...) should not be called, and
  * SIGCHLD should not be ignored or handled because those would prevent SDL
@@ -238,6 +245,7 @@ extern SDL_DECLSPEC SDL_Process * SDLCALL SDL_CreateProcessWithProperties(SDL_Pr
 #define SDL_PROP_PROCESS_CREATE_STDERR_TO_STDOUT_BOOLEAN    "SDL.process.create.stderr_to_stdout"
 #define SDL_PROP_PROCESS_CREATE_BACKGROUND_BOOLEAN          "SDL.process.create.background"
 #define SDL_PROP_PROCESS_CREATE_CMDLINE_STRING              "SDL.process.create.cmdline"
+#define SDL_PROP_PROCESS_CREATE_SDL_IPC                     "SDL.process.create.ipc"
 
 /**
  * Get the properties associated with a process.
@@ -256,6 +264,8 @@ extern SDL_DECLSPEC SDL_Process * SDLCALL SDL_CreateProcessWithProperties(SDL_Pr
  *   `SDL_PROP_PROCESS_CREATE_STDERR_NUMBER` set to `SDL_PROCESS_STDIO_APP`.
  * - `SDL_PROP_PROCESS_BACKGROUND_BOOLEAN`: true if the process is running in
  *   the background.
+ * - `SDL_PROP_PROCESS_SDL_IPC`: true if the process has an IPC channel for
+ *   SDL shared resources.
  *
  * \param process the process to query.
  * \returns a valid property ID on success or 0 on failure; call
@@ -275,6 +285,7 @@ extern SDL_DECLSPEC SDL_PropertiesID SDLCALL SDL_GetProcessProperties(SDL_Proces
 #define SDL_PROP_PROCESS_STDOUT_POINTER     "SDL.process.stdout"
 #define SDL_PROP_PROCESS_STDERR_POINTER     "SDL.process.stderr"
 #define SDL_PROP_PROCESS_BACKGROUND_BOOLEAN "SDL.process.background"
+#define SDL_PROP_PROCESS_SDL_IPC            "SDL.process.ipc"
 
 /**
  * Read all the output from a process.
@@ -432,6 +443,25 @@ extern SDL_DECLSPEC bool SDLCALL SDL_WaitProcess(SDL_Process *process, bool bloc
  */
 extern SDL_DECLSPEC void SDLCALL SDL_DestroyProcess(SDL_Process *process);
 
+/**
+ * Returns a pointer to the process IPC, or NULL if the process has no active
+ * IPC.
+ *
+ * \param process The process to retrieve IPC from.
+ * \returns A handle to the IPC for the given process, or NULL if the process
+ * has no active IPC.
+ */
+extern SDL_DECLSPEC SDL_IPC * SDLCALL SDL_GetProcessIPC(SDL_Process *process);
+
+/**
+ * Returns a pointer to the SDL IPC for the parent process, or NULL if the
+ * parent process did not set up SDL IPC.
+ *
+ * \returns A handle to the IPC of an SDL-based parent, or NULL if no IPC
+ * was found.
+ */
+extern SDL_DECLSPEC SDL_IPC * SDLCALL SDL_GetParentIPC(void);
+
 /* Ends C function definitions when using C++ */
 #ifdef __cplusplus
 }

src/dynapi/SDL_dynapi.sym

@@ -1270,6 +1270,8 @@ SDL3_0.0.0 {
     SDL_RotateSurface;
     SDL_LoadSurface_IO;
     SDL_LoadSurface;
+    SDL_GetProcessIPC;
+    SDL_GetParentIPC;
     # extra symbols go here (don't modify this line)
   local: *;
 };

src/dynapi/SDL_dynapi_overrides.h

@@ -1296,3 +1296,5 @@
 #define SDL_RotateSurface SDL_RotateSurface_REAL
 #define SDL_LoadSurface_IO SDL_LoadSurface_IO_REAL
 #define SDL_LoadSurface SDL_LoadSurface_REAL
+#define SDL_GetProcessIPC SDL_GetProcessIPC_REAL
+#define SDL_GetParentIPC SDL_GetParentIPC_REAL

src/dynapi/SDL_dynapi_procs.h

@@ -1304,3 +1304,5 @@ SDL_DYNAPI_PROC(SDL_Cursor*,SDL_CreateAnimatedCursor,(SDL_CursorFrameInfo *a,int
 SDL_DYNAPI_PROC(SDL_Surface*,SDL_RotateSurface,(SDL_Surface *a,float b),(a,b),return)
 SDL_DYNAPI_PROC(SDL_Surface*,SDL_LoadSurface_IO,(SDL_IOStream *a,bool b),(a,b),return)
 SDL_DYNAPI_PROC(SDL_Surface*,SDL_LoadSurface,(const char *a),(a),return)
+SDL_DYNAPI_PROC(SDL_IPC*,SDL_GetProcessIPC,(SDL_Process *a),(a),return)
+SDL_DYNAPI_PROC(SDL_IPC*,SDL_GetParentIPC,(void),(),return)

src/process/SDL_process.c

@@ -202,3 +202,13 @@ void SDL_DestroyProcess(SDL_Process *process)
     SDL_DestroyProperties(process->props);
     SDL_free(process);
 }
+
+SDL_IPC * SDL_GetProcessIPC(SDL_Process *process)
+{
+    return SDL_SYS_GetProcessIPC(process);
+}
+
+SDL_IPC * SDL_GetParentIPC(void)
+{
+    return SDL_SYS_GetParentIPC();
+}

src/process/SDL_sysprocess.h

@@ -38,5 +38,7 @@ bool SDL_SYS_CreateProcessWithProperties(SDL_Process *process, SDL_PropertiesID
 bool SDL_SYS_KillProcess(SDL_Process *process, bool force);
 bool SDL_SYS_WaitProcess(SDL_Process *process, bool block, int *exitcode);
 void SDL_SYS_DestroyProcess(SDL_Process *process);
+SDL_IPC * SDL_SYS_GetProcessIPC(SDL_Process *process);
+SDL_IPC * SDL_SYS_GetParentIPC(void);
 
 #endif // SDL_sysprocess_h_

src/process/dummy/SDL_dummyprocess.c

@@ -24,7 +24,6 @@
 
 #include "../SDL_sysprocess.h"
 
-
 bool SDL_SYS_CreateProcessWithProperties(SDL_Process *process, SDL_PropertiesID props)
 {
     return SDL_Unsupported();
@@ -45,4 +44,14 @@ void SDL_SYS_DestroyProcess(SDL_Process *process)
     return;
 }
 
+SDL_IPC * SDL_SYS_GetProcessIPC(SDL_Process *process)
+{
+    return NULL;
+}
+
+SDL_IPC * SDL_SYS_GetParentIPC(void)
+{
+    return NULL;
+}
+
 #endif // SDL_PROCESS_DUMMY

src/process/posix/SDL_posixprocess.c

@@ -22,6 +22,8 @@
 
 #ifdef SDL_PROCESS_POSIX
 
+#define SDLIPC_FILENO 3
+
 #include <dirent.h>
 #include <fcntl.h>
 #include <errno.h>
@@ -32,6 +34,8 @@
 #include <string.h>
 #include <unistd.h>
 #include <sys/wait.h>
+#include <sys/socket.h>
+#include <limits.h>
 
 #include "../SDL_sysprocess.h"
 #include "../../io/SDL_iostream_c.h"
@@ -46,8 +50,24 @@
 #define READ_END 0
 #define WRITE_END 1
 
+#define PARENT_END 0
+#define CHILD_END 1
+
+#define SDL_IPC_ENVVAR "_SDL_IPC"
+
+#define _STR(VALUE) #VALUE
+
+// Allows you to stringify the expanded value of a
+// macro
+#define STR(MACRO) _STR(MACRO)
+
+struct SDL_IPC {
+    int socket;
+};
+
 struct SDL_ProcessData {
     pid_t pid;
+    SDL_IPC ipc;
 };
 
 static void CleanupStream(void *userdata, void *value)
@@ -88,6 +108,19 @@ static void IgnoreSignal(int sig)
     }
 }
 
+static bool CreateSockets(int fds[2])
+{
+    if (socketpair(AF_UNIX, SOCK_STREAM, 0, fds) < 0) {
+        return false;
+    }
+
+    // Make sure the pipe isn't accidentally inherited by another thread creating a process
+    fcntl(fds[READ_END], F_SETFD, fcntl(fds[READ_END], F_GETFD) | FD_CLOEXEC);
+    fcntl(fds[WRITE_END], F_SETFD, fcntl(fds[WRITE_END], F_GETFD) | FD_CLOEXEC);
+
+    return true;
+}
+
 static bool CreatePipe(int fds[2])
 {
     if (pipe(fds) < 0) {
@@ -122,14 +155,15 @@ static bool GetStreamFD(SDL_PropertiesID props, const char *property, int *resul
     return true;
 }
 
-static bool AddFileDescriptorCloseActions(posix_spawn_file_actions_t *fa)
+static bool AddFileDescriptorCloseActions(posix_spawn_file_actions_t *fa, bool has_ipc)
 {
     DIR *dir = opendir("/proc/self/fd");
+    const int keep_fileno = has_ipc ? SDLIPC_FILENO : STDERR_FILENO;
     if (dir) {
         struct dirent *entry;
         while ((entry = readdir(dir)) != NULL) {
             int fd = SDL_atoi(entry->d_name);
-            if (fd <= STDERR_FILENO) {
+            if (fd <= keep_fileno) {
                 continue;
             }
 
@@ -144,7 +178,7 @@ static bool AddFileDescriptorCloseActions(posix_spawn_file_actions_t *fa)
         }
         closedir(dir);
     } else {
-        for (int fd = (int)(sysconf(_SC_OPEN_MAX) - 1); fd > STDERR_FILENO; --fd) {
+        for (int fd = (int)(sysconf(_SC_OPEN_MAX) - 1); fd > keep_fileno; --fd) {
             int flags = fcntl(fd, F_GETFD);
             if (flags < 0 || (flags & FD_CLOEXEC)) {
                 continue;
@@ -168,11 +202,22 @@ bool SDL_SYS_CreateProcessWithProperties(SDL_Process *process, SDL_PropertiesID
     SDL_ProcessIO stderr_option = (SDL_ProcessIO)SDL_GetNumberProperty(props, SDL_PROP_PROCESS_CREATE_STDERR_NUMBER, SDL_PROCESS_STDIO_INHERITED);
     bool redirect_stderr = SDL_GetBooleanProperty(props, SDL_PROP_PROCESS_CREATE_STDERR_TO_STDOUT_BOOLEAN, false) &&
                            !SDL_HasProperty(props, SDL_PROP_PROCESS_CREATE_STDERR_NUMBER);
+    bool sdl_ipc = SDL_GetBooleanProperty(props, SDL_PROP_PROCESS_CREATE_SDL_IPC, false);
     int stdin_pipe[2] = { -1, -1 };
     int stdout_pipe[2] = { -1, -1 };
     int stderr_pipe[2] = { -1, -1 };
+    int sockets[2] = { -1, -1 };
     int fd = -1;
 
+    if (sdl_ipc) {
+        // allows children who have already opened a new file descriptor
+        // to distinguish between "fd 3 came from SDL" vs. "fd 3 is the fd I just opened"
+        //
+        // also gives us the option to change fd logic in the future without breaking
+        // clients
+        SDL_SetEnvironmentVariable(env, SDL_IPC_ENVVAR, STR(SDLIPC_FILENO), true);
+    }
+
     // Keep the malloc() before exec() so that an OOM won't run a process at all
     envp = SDL_GetEnvironmentVariables(env);
     if (!envp) {
@@ -296,6 +341,16 @@ bool SDL_SYS_CreateProcessWithProperties(SDL_Process *process, SDL_PropertiesID
         break;
     }
 
+    if (sdl_ipc) {
+        if (!CreateSockets(sockets)) {
+            goto posix_spawn_fail_all;
+        }
+        if (posix_spawn_file_actions_adddup2(&fa, sockets[CHILD_END], SDLIPC_FILENO) != 0) {
+            SDL_SetError("posix_spawn_file_actions_adddup2 failed: %s", strerror(errno));
+            goto posix_spawn_fail_all;
+        }
+    }
+
     if (redirect_stderr) {
         if (posix_spawn_file_actions_adddup2(&fa, STDOUT_FILENO, STDERR_FILENO) != 0) {
             SDL_SetError("posix_spawn_file_actions_adddup2 failed: %s", strerror(errno));
@@ -333,7 +388,7 @@ bool SDL_SYS_CreateProcessWithProperties(SDL_Process *process, SDL_PropertiesID
         }
     }
 
-    if (!AddFileDescriptorCloseActions(&fa)) {
+    if (!AddFileDescriptorCloseActions(&fa, sdl_ipc)) {
         goto posix_spawn_fail_all;
     }
 
@@ -400,6 +455,12 @@ bool SDL_SYS_CreateProcessWithProperties(SDL_Process *process, SDL_PropertiesID
         close(stderr_pipe[WRITE_END]);
     }
 
+    if (sdl_ipc) {
+        data->ipc.socket = sockets[PARENT_END];
+        close(sockets[CHILD_END]);
+    }
+    SDL_SetBooleanProperty(process->props, SDL_PROP_PROCESS_SDL_IPC, sdl_ipc);
+
     posix_spawn_file_actions_destroy(&fa);
     posix_spawnattr_destroy(&attr);
     SDL_free(envp);
@@ -433,6 +494,12 @@ bool SDL_SYS_CreateProcessWithProperties(SDL_Process *process, SDL_PropertiesID
     if (stderr_pipe[WRITE_END] >= 0) {
         close(stderr_pipe[WRITE_END]);
     }
+    if (sockets[PARENT_END] >= 0) {
+        close(sockets[PARENT_END]);
+    }
+    if (sockets[CHILD_END] >= 0) {
+        close(sockets[CHILD_END]);
+    }
     SDL_free(envp);
     return false;
 }
@@ -511,4 +578,55 @@ void SDL_SYS_DestroyProcess(SDL_Process *process)
     SDL_free(process->internal);
 }
 
+SDL_IPC * SDL_SYS_GetProcessIPC(SDL_Process *process)
+{
+    SDL_ProcessData *data = (SDL_ProcessData*)process->internal;
+    return &data->ipc;
+}
+
+SDL_IPC * SDL_SYS_GetParentIPC(void)
+{
+    const char *SDL_GetEnvironmentVariable(SDL_Environment *env, const char *name);
+
+    // hmmmm
+    static SDL_IPC ipc = {
+        .socket = -1,
+    };
+
+    SDL_Environment *env = NULL;
+
+    if (ipc.socket == -1) {
+        env = SDL_GetEnvironment();
+        if (!env) {
+            goto return_null;
+        }
+
+        const char *env_fd = SDL_GetEnvironmentVariable(env, SDL_IPC_ENVVAR);
+        if (!env_fd) {
+            goto destroy_environment;
+        }
+
+        char *end = NULL;
+        long result = strtol(env_fd, &end, 10);
+
+        const bool error = end == NULL
+            || end == env_fd
+            || result > INT_MAX
+            || result < 0;
+
+        if (error) {
+            goto destroy_environment;
+        }
+
+        ipc.socket = (int)result;
+    }
+
+    return &ipc;
+
+destroy_environment:
+    SDL_DestroyEnvironment(env);
+return_null:
+    return NULL;
+}
+
 #endif // SDL_PROCESS_POSIX