output/alsa: add nullptr check for snd_pcm_name() return value

It is not explicitly documented whether snd_pcm_name() is allowed to return NULL: https://www.alsa-project.org/alsa-doc/alsa-lib/group___p_c_m.html#ga5031edc0422df8db1f70af056a12dd77 But apparently this is legal: https://github.com/alsa-project/alsa-lib/blob/0222f45d11e8b71bf651b985b00fdb0addbf3eed/src/pcm/pcm.c#L2761-L2762 That's ... surprising! Closes https://github.com/MusicPlayerDaemon/MPD/issues/1645

output/alsa: add nullptr check for snd_pcm_name() return value
76b25a13 · Max Kellermann · ccc3ee66 · 76b25a13 · 76b25a13
Commit 76b25a13 authored Oct 14, 2022 by Max Kellermann
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NEWS NEWS +2 -0

AlsaOutputPlugin.cxx src/output/plugins/AlsaOutputPlugin.cxx +5 -1

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--- a/NEWS
+++ b/NEWS
@@ -5,6 +5,8 @@ ver 0.23.10 (not yet released)
  - ffmpeg: fix libfmt 9 compiler warning
 * encoder
  - flac: fix failure when libFLAC is built without Ogg support
+* output
+  - alsa: fix crash bug
 * Windows
  - log to stdout by default, don't require "log_file" setting


--- a/src/output/plugins/AlsaOutputPlugin.cxx
+++ b/src/output/plugins/AlsaOutputPlugin.cxx
@@ -812,8 +812,12 @@ AlsaOutput::Open(AudioFormat &audio_format)
 				      fmt::format("Failed to open ALSA device \"{}\"",
 						  GetDevice()).c_str());

+	const char *pcm_name = snd_pcm_name(pcm);
+	if (pcm_name == nullptr)
+		pcm_name = "?";
+
 	FmtDebug(alsa_output_domain, "opened {} type={}",
-		 snd_pcm_name(pcm),
+		 pcm_name,
 		 snd_pcm_type_name(snd_pcm_type(pcm)));

 #ifdef ENABLE_DSD