tidy-up: example, tests continued

- fix skip auth if `userauthlist` is NULL.
  Closes #836 (Reported-by: @sudipm-mukherjee on github)
- fix most silenced `checksrc` warnings.
- sync examples/tests code between each other.
  (output messages, error handling, declaration order, comments)
- stop including unnecessary headers.
- always deinitialize in case of error.
- drop some redundant variables.
- add error handling where missing.
- show more error codes.
- switch `perror()` to `fprintf()`.
- fix some `printf()`s to be `fprintf()`.
- formatting.

Closes #960

example/scp_nonblock.c

@@ -4,7 +4,7 @@
  * The sample code has default values for host name, user name, password
  * and path to copy, but you can specify them on the command line like:
  *
- * "scp_nonblock 192.168.0.1 user password /tmp/secrets"
+ * $ ./scp_nonblock 192.168.0.1 user password /tmp/secrets
  */
 
 #include "libssh2_setup.h"
@@ -39,12 +39,18 @@
 #include <stdio.h>
 #include <ctype.h>
 
+static const char *pubkey = "/home/username/.ssh/id_rsa.pub";
+static const char *privkey = "/home/username/.ssh/id_rsa";
+static const char *username = "username";
+static const char *password = "password";
+static const char *scppath = "/tmp/TEST";
+
 #ifdef HAVE_GETTIMEOFDAY
 /* diff in ms */
 static long tvdiff(struct timeval newer, struct timeval older)
 {
-    return (newer.tv_sec-older.tv_sec)*1000+
-        (newer.tv_usec-older.tv_usec)/1000;
+    return (newer.tv_sec - older.tv_sec) * 1000 +
+        (newer.tv_usec - older.tv_usec) / 1000;
 }
 #endif
 
@@ -85,31 +91,25 @@ int main(int argc, char *argv[])
     int i, auth_pw = 1;
     struct sockaddr_in sin;
     const char *fingerprint;
-    LIBSSH2_SESSION *session;
+    int rc;
+    LIBSSH2_SESSION *session = NULL;
     LIBSSH2_CHANNEL *channel;
-    const char *pubkey = "/home/username/.ssh/id_rsa.pub";
-    const char *privkey = "/home/username/.ssh/id_rsa";
-    const char *username = "username";
-    const char *password = "password";
-    const char *scppath = "/tmp/TEST";
     libssh2_struct_stat fileinfo;
 #ifdef HAVE_GETTIMEOFDAY
     struct timeval start;
     struct timeval end;
     long time_ms;
 #endif
-    int rc;
     int spin = 0;
     libssh2_struct_stat_size got = 0;
     libssh2_struct_stat_size total = 0;
 
 #ifdef WIN32
     WSADATA wsadata;
-    int err;
 
-    err = WSAStartup(MAKEWORD(2, 0), &wsadata);
-    if(err != 0) {
-        fprintf(stderr, "WSAStartup failed with error: %d\n", err);
+    rc = WSAStartup(MAKEWORD(2, 0), &wsadata);
+    if(rc) {
+        fprintf(stderr, "WSAStartup failed with error: %d\n", rc);
         return 1;
     }
 #endif
@@ -131,29 +131,34 @@ int main(int argc, char *argv[])
     }
 
     rc = libssh2_init(0);
-    if(rc != 0) {
+    if(rc) {
         fprintf(stderr, "libssh2 initialization failed (%d)\n", rc);
         return 1;
     }
 
-    /* Ultra basic "connect to port 22 on localhost"
-     * Your code is responsible for creating the socket establishing the
-     * connection
+    /* Ultra basic "connect to port 22 on localhost".  Your code is
+     * responsible for creating the socket establishing the connection
      */
     sock = socket(AF_INET, SOCK_STREAM, 0);
+    if(sock == LIBSSH2_INVALID_SOCKET) {
+        fprintf(stderr, "failed to create socket!\n");
+        goto shutdown;
+    }
 
     sin.sin_family = AF_INET;
     sin.sin_port = htons(22);
     sin.sin_addr.s_addr = hostaddr;
     if(connect(sock, (struct sockaddr*)(&sin), sizeof(struct sockaddr_in))) {
         fprintf(stderr, "failed to connect!\n");
-        return -1;
+        goto shutdown;
     }
 
     /* Create a session instance */
     session = libssh2_session_init();
-    if(!session)
-        return -1;
+    if(!session) {
+        fprintf(stderr, "Could not initialize SSH session!\n");
+        goto shutdown;
+    }
 
     /* Since we have set non-blocking, tell libssh2 we are non-blocking */
     libssh2_session_set_blocking(session, 0);
@@ -169,14 +174,14 @@ int main(int argc, char *argv[])
           LIBSSH2_ERROR_EAGAIN);
     if(rc) {
         fprintf(stderr, "Failure establishing SSH session: %d\n", rc);
-        return -1;
+        goto shutdown;
     }
 
     /* At this point we have not yet authenticated.  The first thing to do
-        * is check the hostkey's fingerprint against our known hosts Your app
-        * may have it hard coded, may go to a file, may present it to the
-        * user, that's your call
-        */
+     * is check the hostkey's fingerprint against our known hosts Your app
+     * may have it hard coded, may go to a file, may present it to the
+     * user, that's your call
+     */
     fingerprint = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_SHA1);
     fprintf(stderr, "Fingerprint: ");
     for(i = 0; i < 20; i++) {
@@ -189,7 +194,7 @@ int main(int argc, char *argv[])
         while((rc = libssh2_userauth_password(session, username, password)) ==
               LIBSSH2_ERROR_EAGAIN);
         if(rc) {
-            fprintf(stderr, "Authentication by password failed.\n");
+            fprintf(stderr, "Authentication by password failed!\n");
             goto shutdown;
         }
     }
@@ -200,7 +205,7 @@ int main(int argc, char *argv[])
                                                         password)) ==
               LIBSSH2_ERROR_EAGAIN);
         if(rc) {
-            fprintf(stderr, "\tAuthentication by public key failed\n");
+            fprintf(stderr, "Authentication by public key failed!\n");
             goto shutdown;
         }
     }
@@ -231,13 +236,13 @@ int main(int argc, char *argv[])
     fprintf(stderr, "libssh2_scp_recv() is done, now receive data!\n");
 
     while(got < fileinfo.st_size) {
-        char mem[1024*24];
+        char mem[1024 * 24];
         ssize_t nread;
 
         do {
             int amount = sizeof(mem);
 
-            if((fileinfo.st_size -got) < amount) {
+            if((fileinfo.st_size - got) < amount) {
                 amount = (int)(fileinfo.st_size - got);
             }
 
@@ -250,7 +255,7 @@ int main(int argc, char *argv[])
             }
         } while(nread > 0);
 
-        if((nread == LIBSSH2_ERROR_EAGAIN) && (got < fileinfo.st_size)) {
+        if(nread == LIBSSH2_ERROR_EAGAIN && got < fileinfo.st_size) {
             /* this is due to blocking that would occur otherwise
             so we loop on this condition */
 
@@ -267,7 +272,7 @@ int main(int argc, char *argv[])
     time_ms = tvdiff(end, start);
     fprintf(stderr, "Got %ld bytes in %ld ms = %.1f bytes/sec spin: %d\n",
             (long)total, time_ms,
-            (double)total/((double)time_ms/1000.0), spin);
+            (double)total / ((double)time_ms / 1000.0), spin);
 #else
     fprintf(stderr, "Got %ld bytes spin: %d\n", (long)total, spin);
 #endif
@@ -277,14 +282,19 @@ int main(int argc, char *argv[])
 
 shutdown:
 
-    libssh2_session_disconnect(session, "Normal Shutdown");
-    libssh2_session_free(session);
+    if(session) {
+        libssh2_session_disconnect(session, "Normal Shutdown");
+        libssh2_session_free(session);
+    }
 
+    if(sock != LIBSSH2_INVALID_SOCKET) {
 #ifdef WIN32
-    closesocket(sock);
+        closesocket(sock);
 #else
-    close(sock);
+        close(sock);
 #endif
+    }
+
     fprintf(stderr, "all done\n");
 
     libssh2_exit();