From: David Herrmann <dh.herrmann@gmail.com>
Date: Wed, 15 Jul 2015 10:30:08 +0000 (+0200)
Subject: sd-device: never return NULL+0
X-Git-Tag: v226.4~1^2~209
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=commitdiff_plain;h=f6035a5ec8045bf007c7ebc5ee5306418644e7aa;hp=ffd9a99e116775904762b688b2caabbc61e74c82

sd-device: never return NULL+0

It is highly confusing if a getter function returns 0, but the value is
set to NULL. This, right now, triggers assertions as code relies on the
returned values to be non-NULL.

Like with sd-bus-creds and friends, return 0 only if a value is actually
available.

Discussed with Tom, and actually fixes real bugs as in #512.
---

diff --git a/src/libelogind/sd-device/sd-device.c b/src/libelogind/sd-device/sd-device.c
index b274f7109..7cea5a074 100644
--- a/src/libelogind/sd-device/sd-device.c
+++ b/src/libelogind/sd-device/sd-device.c
@@ -791,6 +791,9 @@ _public_ int sd_device_get_subsystem(sd_device *device, const char **ret) {
                 device->subsystem_set = true;
         }
 
+        if (!device->subsystem)
+                return -ENOENT;
+
         *ret = device->subsystem;
 
         return 0;
@@ -908,6 +911,9 @@ _public_ int sd_device_get_driver(sd_device *device, const char **ret) {
                         return log_debug_errno(r, "sd-device: could not set driver for %s: %m", device->devpath);
         }
 
+        if (!device->driver)
+                return -ENOENT;
+
         *ret = device->driver;
 
         return 0;
@@ -1002,6 +1008,8 @@ _public_ int sd_device_get_sysname(sd_device *device, const char **ret) {
                         return r;
         }
 
+        assert_return(device->sysname, -ENOENT);
+
         *ret = device->sysname;
 
         return 0;