Handle some unchecked malloc() calls. Closes eclipse-mosquitto#1.

Thanks to Markus Elfring.

ChangeLog.txt

@@ -15,6 +15,8 @@ Client library:
 - Fix the case where a message received just before the keepalive timer
   expired would cause the client to miss the keepalive timer.
 
+Clients:
+- Handle some unchecked malloc() calls. Closes #1.
 
 1.4.8 - 20160214
 ================

client/client_shared.c

@@ -115,6 +115,10 @@ int client_config_load(struct mosq_config *cfg, int pub_or_sub, int argc, char *
 	if(env){
 		len = strlen(env) + strlen("/mosquitto_pub") + 1;
 		loc = malloc(len);
+		if(!loc){
+			fprintf(stderr, "Error: Out of memory.\n");
+			return 1;
+		}
 		if(pub_or_sub == CLIENT_PUB){
 			snprintf(loc, len, "%s/mosquitto_pub", env);
 		}else{
@@ -126,6 +130,10 @@ int client_config_load(struct mosq_config *cfg, int pub_or_sub, int argc, char *
 		if(env){
 			len = strlen(env) + strlen("/.config/mosquitto_pub") + 1;
 			loc = malloc(len);
+			if(!loc){
+				fprintf(stderr, "Error: Out of memory.\n");
+				return 1;
+			}
 			if(pub_or_sub == CLIENT_PUB){
 				snprintf(loc, len, "%s/.config/mosquitto_pub", env);
 			}else{
@@ -142,6 +150,10 @@ int client_config_load(struct mosq_config *cfg, int pub_or_sub, int argc, char *
 	if(rc > 0 && rc < 1024){
 		len = strlen(env) + strlen("\\mosquitto_pub.conf") + 1;
 		loc = malloc(len);
+		if(!loc){
+			fprintf(stderr, "Error: Out of memory.\n");
+			return 1;
+		}
 		if(pub_or_sub == CLIENT_PUB){
 			snprintf(loc, len, "%s\\mosquitto_pub.conf", env);
 		}else{