From 7e43b2a6792b81166bc63153c09646865bf984da Mon Sep 17 00:00:00 2001
From: Jeremy Sowden <jeremy@azazel.net>
Date: Sat, 18 Apr 2020 18:03:42 +0100
Subject: [PATCH] wmix: fix multiple definitions of global variables.

The mixer API variables are declared in a header with no explicit
linkage.  This results in there being definitions of them in multiple
object files, which causes a link failure with GCC 10, since this
uses -fno-common by default.

Add `extern` to the header declarations and separate declarations with
no linkage in mixer.c where they are assigned.

Link: https://bugs.debian.org/957947
Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
---
 wmix/include/mixer.h | 50 ++++++++++++++++++++++----------------------
 wmix/wmix.c          | 25 ++++++++++++++++++++++
 2 files changed, 50 insertions(+), 25 deletions(-)

diff --git a/wmix/include/mixer.h b/wmix/include/mixer.h
index 116d8ed..fa567a2 100644
--- a/wmix/include/mixer.h
+++ b/wmix/include/mixer.h
@@ -55,28 +55,28 @@
  * - Muting must occur independently of the volume level.
  */
 
-void (*mixer_init)(const char *mixer_device,
-                   bool verbose,
-                   const char *exclude[]);
-bool (*mixer_is_changed)(void);
-int (*mixer_get_channel_count)(void);
-int (*mixer_get_channel)(void);
-const char *(*mixer_get_channel_name)(void);
-const char *(*mixer_get_short_name)(void);
-void (*mixer_set_channel)(int channel);
-void (*mixer_set_channel_rel)(int delta_channel);
-float (*mixer_get_volume)(void);
-void (*mixer_set_volume)(float volume);
-void (*mixer_set_volume_rel)(float delta_volume);
-float (*mixer_get_balance)(void);
-void (*mixer_set_balance)(float balance);
-void (*mixer_set_balance_rel)(float delta_balance);
-void (*mixer_toggle_mute)(void);
-void (*mixer_toggle_rec)(void);
-bool (*mixer_is_muted)(void);
-bool (*mixer_is_stereo)(void);
-bool (*mixer_is_rec)(void);
-bool (*mixer_can_rec)(void);
-bool (*is_exclude)(const char *short_name,
-                   const char *exclude[]);
-void (*mixer_tick)(void);
+extern void (*mixer_init)(const char *mixer_device,
+                          bool verbose,
+                          const char *exclude[]);
+extern bool (*mixer_is_changed)(void);
+extern int (*mixer_get_channel_count)(void);
+extern int (*mixer_get_channel)(void);
+extern const char *(*mixer_get_channel_name)(void);
+extern const char *(*mixer_get_short_name)(void);
+extern void (*mixer_set_channel)(int channel);
+extern void (*mixer_set_channel_rel)(int delta_channel);
+extern float (*mixer_get_volume)(void);
+extern void (*mixer_set_volume)(float volume);
+extern void (*mixer_set_volume_rel)(float delta_volume);
+extern float (*mixer_get_balance)(void);
+extern void (*mixer_set_balance)(float balance);
+extern void (*mixer_set_balance_rel)(float delta_balance);
+extern void (*mixer_toggle_mute)(void);
+extern void (*mixer_toggle_rec)(void);
+extern bool (*mixer_is_muted)(void);
+extern bool (*mixer_is_stereo)(void);
+extern bool (*mixer_is_rec)(void);
+extern bool (*mixer_can_rec)(void);
+extern bool (*is_exclude)(const char *short_name,
+                          const char *exclude[]);
+extern void (*mixer_tick)(void);
diff --git a/wmix/wmix.c b/wmix/wmix.c
index a26cab8..c42c978 100644
--- a/wmix/wmix.c
+++ b/wmix/wmix.c
@@ -41,6 +41,31 @@
 #include "include/mixer-oss.h"
 #include "include/mixer-alsa.h"
 
+void (*mixer_init)(const char *mixer_device,
+                   bool verbose,
+                   const char *exclude[]);
+bool (*mixer_is_changed)(void);
+int (*mixer_get_channel_count)(void);
+int (*mixer_get_channel)(void);
+const char *(*mixer_get_channel_name)(void);
+const char *(*mixer_get_short_name)(void);
+void (*mixer_set_channel)(int channel);
+void (*mixer_set_channel_rel)(int delta_channel);
+float (*mixer_get_volume)(void);
+void (*mixer_set_volume)(float volume);
+void (*mixer_set_volume_rel)(float delta_volume);
+float (*mixer_get_balance)(void);
+void (*mixer_set_balance)(float balance);
+void (*mixer_set_balance_rel)(float delta_balance);
+void (*mixer_toggle_mute)(void);
+void (*mixer_toggle_rec)(void);
+bool (*mixer_is_muted)(void);
+bool (*mixer_is_stereo)(void);
+bool (*mixer_is_rec)(void);
+bool (*mixer_can_rec)(void);
+bool (*is_exclude)(const char *short_name,
+                   const char *exclude[]);
+void (*mixer_tick)(void);
 
 static Display *display;
 static bool button_pressed = false;