Fix core file not generating on OSX

When reading memory segments, reset the return value kr so that the
generated file is not deleted at the end if the last memory segment
throws an error when being read, since mach_vm_read errors are not
fatal.

Also make sure final return value is correct when there is an error.

Signed-off-by: Mike Zhang <mike.h.zhang@ibm.com>

port/osx/omrosdump.c

@@ -84,6 +84,7 @@ coredump_to_file(mach_port_t task_port, pid_t pid)
 
 	if (-1 == corefile_fd) {
 		perror("open()");
+		kr = KERN_FAILURE;
 		goto done;
 	}
 
@@ -192,6 +193,8 @@ coredump_to_file(mach_port_t task_port, pid_t pid)
 
 		seg_file_off += segments[i].vmsize;
 		file_off += sizeof(struct segment_command_64);
+
+		kr = KERN_SUCCESS; /* reset kr since a failure from mach_vm_read is not fatal */
 	}
 
 	mh64.ncmds += segment_count;
@@ -409,49 +412,51 @@ omrdump_create(struct OMRPortLibrary *portLibrary, char *filename, char *dumpTyp
 	mach_port_t pass_port = MACH_PORT_NULL;
 	mach_port_t special_port = MACH_PORT_NULL;
 
-	/* set core name, defaults to "core.%u" if none given */
-	if (NULL == filename || ('\0' == filename[0])) {
-		snprintf(corefile_name, PATH_MAX, "core.%u", parent_pid);
+	/* filename cannot be null */
+	if (NULL == filename) {
+		return 1;
+	}
+	/* set default file name if none given */
+	if ('\0' == filename[0]) {
+		snprintf(filename, PATH_MAX, "core.%u", parent_pid);
+	}
+	lastSep = strrchr(filename, DIR_SEPARATOR);
+	if (NULL != lastSep) {
+		strncpy(corefile_name, lastSep + 1, PATH_MAX);
 	} else {
-		lastSep = strrchr(filename, DIR_SEPARATOR);
-		if (NULL != lastSep) {
-			strncpy(corefile_name, lastSep + 1, PATH_MAX);
-		} else {
-			strncpy(corefile_name, filename, PATH_MAX);
-		}
+		strncpy(corefile_name, filename, PATH_MAX);
 	}
 
 	/* save the original special port so we can restore it after using it to pass the task port */
 	kr = task_get_bootstrap_port(mach_task_self(), &special_port);
 	if (KERN_SUCCESS != kr) {
 		mach_error("failed get special port:\n", kr);
-		return kr;
+		goto done;
 	}
 	pass_port = mach_task_self();
 	/* pass parent task port to child through special port inheritance */
 	kr = task_set_bootstrap_port(mach_task_self(), pass_port);
 	if (KERN_SUCCESS != kr) {
 		mach_error("failed set special port:\n", kr);
-		return kr;
+		goto done;
 	}
 
 	child_pid = fork();
 	if (0 == child_pid) { /* in child process */
 		kr = task_get_bootstrap_port(mach_task_self(), &pass_port);
 		if (KERN_SUCCESS != kr) {
 			mach_error("failed get special port:\n", kr);
-			return kr;
-		}
-		/* Move to specified folder before dumping */
-		if (NULL != lastSep) {
-			/* keep separator for cases such as when the path is '/' */
-			lastSep[1] = '\0';
-			if (0 != chdir(filename)) {
-				perror("failed to change directories for dump");
-				return KERN_FAILURE;
+		} else {
+			/* Move to specified folder before dumping */
+			if (NULL != lastSep) {
+				/* keep separator for cases such as when the path is '/' */
+				lastSep[1] = '\0';
+				if (0 != chdir(filename)) {
+					perror("failed to change directories, attempting to create dump in current dir");
+				}
 			}
+			kr = coredump_to_file(pass_port, parent_pid);
 		}
-		kr = coredump_to_file(pass_port, parent_pid);
 		raise(SIGKILL); /* kill child process without running any exit procedures */
 	} else if (child_pid < 0) { /* fork failed */
 		perror("forking for core dump failed");
@@ -461,11 +466,22 @@ omrdump_create(struct OMRPortLibrary *portLibrary, char *filename, char *dumpTyp
 		kr = task_set_bootstrap_port(mach_task_self(), special_port);
 		if (KERN_SUCCESS != kr) {
 			mach_error("failed set special port:\n", kr);
-			return kr;
+			goto done;
 		}
 	} /* 0 == child_pid */
 
-	return kr;
+done:
+	if (KERN_SUCCESS == kr) {
+		/* check if the core file has been created in the right directory */
+		if (0 == access(filename, F_OK)) {
+			return 0;
+		}
+		/* check for corefile in current working directory */
+		if ((NULL != lastSep) && (0 == access(corefile_name, F_OK))) {
+			return 0;
+		}
+	}
+	return 1;
 }
 
 int32_t