macOS Semaphore Cleanup

macOS uses GCD for threading and semaphores, but they aren't quite like
POSIX semaphores. macOS allows the use of named POSIX semaphores.

1. Convert the semaphores to named POSIX semaphores.
2. Simplify all calls for semaphores into single function calls of the
   wrapper API.
3. Update both examples/client/client.c and apps/wolfssh/wolfssh.c.
4. Update both to deregister the WINCH signal.

apps/wolfssh/wolfssh.c

@@ -272,22 +272,70 @@ static int sendCurrentWindowSize(thread_args* args)
 
 #ifndef _MSC_VER
 
-#if (defined(__OSX__) || defined(__APPLE__))
-#include <dispatch/dispatch.h>
-dispatch_semaphore_t windowSem;
-#else
+#include <errno.h>
+#include <fcntl.h>
 #include <semaphore.h>
-static sem_t windowSem;
-#endif
+#include <stdio.h>
+#include <unistd.h>
+
+typedef struct {
+    sem_t* s;
+    char name[32];
+} WOLFSSH_SEMAPHORE;
+
+static inline
+int wolfSSH_SEMAPHORE_Init(WOLFSSH_SEMAPHORE* s, unsigned int n)
+{
+    if (s != NULL) {
+        snprintf(s->name, sizeof(s->name), "/wolfssh_winch_%d", (int)getpid());
+        s->s = sem_open(s->name, O_CREAT | O_EXCL | O_RDWR, 0600, n);
+        if (s->s == SEM_FAILED && errno == EEXIST) {
+            /* named semaphore already exists, unlink the name and
+             * try to open it one more time. */
+            if (sem_unlink(s->name) == 0) {
+                s->s = sem_open(s->name, O_CREAT | O_RDWR, 0600, n);
+            }
+        }
+    }
+    return (s != NULL && s->s != SEM_FAILED);
+}
+
+static inline
+void wolfSSH_SEMAPHORE_Release(WOLFSSH_SEMAPHORE* s)
+{
+    if (s != NULL && s->s != NULL && s->s != SEM_FAILED) {
+        sem_close(s->s);
+        sem_unlink(s->name);
+        s->s = NULL;
+    }
+}
+
+static inline
+int wolfSSH_SEMAPHORE_Wait(WOLFSSH_SEMAPHORE* s)
+{
+    int ret = -1;
+    if (s != NULL && s->s != NULL && s->s != SEM_FAILED) {
+        do {
+            ret = sem_wait(s->s);
+        } while (ret == -1 && errno == EINTR);
+    }
+    return (ret == 0);
+}
+
+static inline
+void wolfSSH_SEMAPHORE_Post(WOLFSSH_SEMAPHORE* s)
+{
+    if (s != NULL && s->s != NULL && s->s != SEM_FAILED) {
+        sem_post(s->s);
+    }
+}
+
+static WOLFSSH_SEMAPHORE windowSem;
 
 /* capture window change signals */
 static void WindowChangeSignal(int sig)
 {
-#if (defined(__OSX__) || defined(__APPLE__))
-    dispatch_semaphore_signal(windowSem);
-#else
-    sem_post(&windowSem);
-#endif
+    wolfSSH_SEMAPHORE_Post(&windowSem);
     (void)sig;
 }
 
@@ -299,11 +347,9 @@ static THREAD_RET windowMonitor(void* in)
 
     args = (thread_args*)in;
     do {
-    #if (defined(__OSX__) || defined(__APPLE__))
-        dispatch_semaphore_wait(windowSem, DISPATCH_TIME_FOREVER);
-    #else
-        sem_wait(&windowSem);
-    #endif
+        if (!wolfSSH_SEMAPHORE_Wait(&windowSem)) {
+            break;
+        }
         if (args->quit) {
             break;
         }
@@ -1060,11 +1106,9 @@ static THREAD_RETURN WOLFSSH_THREAD wolfSSH_Client(void* args)
         arg.readError = 0;
 #ifdef WOLFSSH_TERM
         arg.quit = 0;
-    #if (defined(__OSX__) || defined(__APPLE__))
-        windowSem = dispatch_semaphore_create(0);
-    #else
-        sem_init(&windowSem, 0, 0);
-    #endif
+        if (!wolfSSH_SEMAPHORE_Init(&windowSem, 0)) {
+            err_sys("Couldn't initialize window semaphore.");
+        }
 
         if (config.command) {
             int err;
@@ -1087,21 +1131,14 @@ static THREAD_RETURN WOLFSSH_THREAD wolfSSH_Client(void* args)
 #ifdef WOLFSSH_TERM
         /* Wake the windowMonitor thread so it can exit. */
         arg.quit = 1;
-    #if (defined(__OSX__) || defined(__APPLE__))
-        dispatch_semaphore_signal(windowSem);
-    #else
-        sem_post(&windowSem);
-    #endif
+        signal(SIGWINCH, SIG_DFL);
+        wolfSSH_SEMAPHORE_Post(&windowSem);
         pthread_join(thread[0], NULL);
 #endif /* WOLFSSH_TERM */
         pthread_cancel(thread[1]);
         pthread_join(thread[1], NULL);
 #ifdef WOLFSSH_TERM
-    #if (defined(__OSX__) || defined(__APPLE__))
-        dispatch_release(windowSem);
-    #else
-        sem_destroy(&windowSem);
-    #endif
+        wolfSSH_SEMAPHORE_Release(&windowSem);
 #endif /* WOLFSSH_TERM */
         ioErr = arg.readError;
     #elif defined(_MSC_VER)

examples/client/client.c

@@ -240,22 +240,70 @@ static int sendCurrentWindowSize(thread_args* args)
 #ifdef WOLFSSH_TERM
 #ifndef _MSC_VER
 
-#if (defined(__OSX__) || defined(__APPLE__))
-#include <dispatch/dispatch.h>
-dispatch_semaphore_t windowSem;
-#else
+#include <errno.h>
+#include <fcntl.h>
 #include <semaphore.h>
-static sem_t windowSem;
-#endif
+#include <stdio.h>
+#include <unistd.h>
+
+typedef struct {
+    sem_t* s;
+    char name[32];
+} WOLFSSH_SEMAPHORE;
+
+static inline
+int wolfSSH_SEMAPHORE_Init(WOLFSSH_SEMAPHORE* s, unsigned int n)
+{
+    if (s != NULL) {
+        snprintf(s->name, sizeof(s->name), "/wolfssh_winch_%d", (int)getpid());
+        s->s = sem_open(s->name, O_CREAT | O_EXCL | O_RDWR, 0600, n);
+        if (s->s == SEM_FAILED && errno == EEXIST) {
+            /* named semaphore already exists, unlink the name and
+             * try to open it one more time. */
+            if (sem_unlink(s->name) == 0) {
+                s->s = sem_open(s->name, O_CREAT | O_RDWR, 0600, n);
+            }
+        }
+    }
+    return (s != NULL && s->s != SEM_FAILED);
+}
+
+static inline
+void wolfSSH_SEMAPHORE_Release(WOLFSSH_SEMAPHORE* s)
+{
+    if (s != NULL && s->s != NULL && s->s != SEM_FAILED) {
+        sem_close(s->s);
+        sem_unlink(s->name);
+        s->s = NULL;
+    }
+}
+
+static inline
+int wolfSSH_SEMAPHORE_Wait(WOLFSSH_SEMAPHORE* s)
+{
+    int ret = -1;
+    if (s != NULL && s->s != NULL && s->s != SEM_FAILED) {
+        do {
+            ret = sem_wait(s->s);
+        } while (ret == -1 && errno == EINTR);
+    }
+    return (ret == 0);
+}
+
+static inline
+void wolfSSH_SEMAPHORE_Post(WOLFSSH_SEMAPHORE* s)
+{
+    if (s != NULL && s->s != NULL && s->s != SEM_FAILED) {
+        sem_post(s->s);
+    }
+}
+
+static WOLFSSH_SEMAPHORE windowSem;
 
 /* capture window change signals */
 static void WindowChangeSignal(int sig)
 {
-#if (defined(__OSX__) || defined(__APPLE__))
-    dispatch_semaphore_signal(windowSem);
-#else
-    sem_post(&windowSem);
-#endif
+    wolfSSH_SEMAPHORE_Post(&windowSem);
     (void)sig;
 }
 
@@ -267,11 +315,9 @@ static THREAD_RET windowMonitor(void* in)
 
     args = (thread_args*)in;
     do {
-    #if (defined(__OSX__) || defined(__APPLE__))
-        dispatch_semaphore_wait(windowSem, DISPATCH_TIME_FOREVER);
-    #else
-        sem_wait(&windowSem);
-    #endif
+        if (!wolfSSH_SEMAPHORE_Wait(&windowSem)) {
+            break;
+        }
         if (args->quit) {
             break;
         }
@@ -1032,11 +1078,9 @@ THREAD_RETURN WOLFSSH_THREAD client_test(void* args)
         arg.quit = 0;
         wc_InitMutex(&arg.lock);
 #ifdef WOLFSSH_TERM
-    #if (defined(__OSX__) || defined(__APPLE__))
-        windowSem = dispatch_semaphore_create(0);
-    #else
-        sem_init(&windowSem, 0, 0);
-    #endif
+        if (!wolfSSH_SEMAPHORE_Init(&windowSem, 0)) {
+            err_sys("Couldn't initialize window semaphore.");
+        }
 
         if (cmd) {
             int err;
@@ -1057,21 +1101,14 @@ THREAD_RETURN WOLFSSH_THREAD client_test(void* args)
 #ifdef WOLFSSH_TERM
         /* Wake the windowMonitor thread so it can exit. */
         arg.quit = 1;
-    #if (defined(__OSX__) || defined(__APPLE__))
-        dispatch_semaphore_signal(windowSem);
-    #else
-        sem_post(&windowSem);
-    #endif
+        signal(SIGWINCH, SIG_DFL);
+        wolfSSH_SEMAPHORE_Post(&windowSem);
         pthread_join(thread[0], NULL);
 #endif /* WOLFSSH_TERM */
         pthread_cancel(thread[1]);
         pthread_join(thread[1], NULL);
 #ifdef WOLFSSH_TERM
-    #if (defined(__OSX__) || defined(__APPLE__))
-        dispatch_release(windowSem);
-    #else
-        sem_destroy(&windowSem);
-    #endif
+        wolfSSH_SEMAPHORE_Release(&windowSem);
 #endif /* WOLFSSH_TERM */
     #elif defined(_MSC_VER)
         thread_args arg;