check asprintf return value

The current asprintf usage triggers many warnings like:

sslh-main.c: In function 'print_usage':
sslh-main.c:86:17: warning: ignoring return value of 'asprintf',
	declared with attribute warn_unused_result [-Wunused-result]

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

common.c

@@ -487,9 +487,11 @@ void setup_signals(void)
  * banner is made up of basename(bin_name)+"[pid]" */
 void setup_syslog(const char* bin_name) {
     char *name1, *name2;
+    int res;
 
     name1 = strdup(bin_name);
-    asprintf(&name2, "%s[%d]", basename(name1), getpid());
+    res = asprintf(&name2, "%s[%d]", basename(name1), getpid());
+    CHECK_RES_DIE(res, "asprintf");
     openlog(name2, LOG_CONS, LOG_AUTH);
     free(name1); 
     /* Don't free name2, as openlog(3) uses it (at least in glibc) */

probe.c

@@ -63,7 +63,8 @@ int get_num_builtins(void) {
 /* Sets the protocol name to connect to in case of timeout */
 void set_ontimeout(const char* name)
 {
-    asprintf(&on_timeout, "%s", name);
+    int res = asprintf(&on_timeout, "%s", name);
+    CHECK_RES_DIE(res, "asprintf");
 }
 
 /* Returns the protocol to connect to in case of timeout; 

sslh-main.c

@@ -79,11 +79,14 @@ static void print_usage(void)
 {
     struct proto *p;
     int i;
+    int res;
     char *prots = "";
 
     p = get_builtins();
-    for (i = 0; i < get_num_builtins(); i++)
-        asprintf(&prots, "%s\t[--%s <addr>]\n", prots, p[i].description);
+    for (i = 0; i < get_num_builtins(); i++) {
+        res = asprintf(&prots, "%s\t[--%s <addr>]\n", prots, p[i].description);
+        CHECK_RES_DIE(res, "asprintf");
+    }
 
     fprintf(stderr, USAGE_STRING, prots);
 }