From: Jaroslav Kysela <perex@perex.cz>
Date: Tue, 17 May 2022 12:35:51 +0000 (+0200)
Subject: ucm: allow '-' prefix to avoid errors when the variable is not defined
X-Git-Tag: v1.2.7~34
X-Git-Url: https://git.alsa-project.org/?a=commitdiff_plain;h=5062565e824f02c9838bd781862a9396c52d4111;p=alsa-lib.git

ucm: allow '-' prefix to avoid errors when the variable is not defined

It may be useful to check if variable is not defined.

Signed-off-by: Jaroslav Kysela <perex@perex.cz>
---

diff --git a/src/ucm/ucm_subs.c b/src/ucm/ucm_subs.c
index 8b42b889..a7d79430 100644
--- a/src/ucm/ucm_subs.c
+++ b/src/ucm/ucm_subs.c
@@ -549,13 +549,20 @@ static char *rval_sysfs(snd_use_case_mgr_t *uc_mgr ATTRIBUTE_UNUSED, const char
 static char *rval_var(snd_use_case_mgr_t *uc_mgr, const char *id)
 {
 	const char *v;
+	bool ignore_not_found = false;
 
 	if (uc_mgr->conf_format < 3) {
 		uc_error("variable substitution is supported in v3+ syntax");
 		return NULL;
 	}
 
+	if (id[0] == '-') {
+		ignore_not_found = true;
+		id++;
+	}
 	v = uc_mgr_get_variable(uc_mgr, id);
+	if (v == NULL && ignore_not_found)
+		v = "";
 	if (v)
 		return strdup(v);
 	return NULL;