Taken from: https://sources.debian.org/patches/barcode/0.99-4/0006-Fix-FTBFS-with-gcc-10.patch/
Author: https://sources.debian.org/patches/barcode/0.99-4/0006-Fix-FTBFS-with-gcc-10.patch/
--- a/barcode.h
+++ b/barcode.h
@@ -123,6 +123,6 @@ extern int Barcode_Version(char *versionname);
 }
 #endif
 
-int streaming;
+extern int streaming;
 
 #endif /* _BARCODE_H_ */
diff --git a/library.c b/library.c
index 30946ff..5390a2b 100644
--- a/library.c
+++ b/library.c
@@ -30,6 +30,8 @@
 #endif
 #include <errno.h>
 
+int streaming;
+
 /*
  * This function allocates a barcode structure and strdup()s the
  * text string. It returns NULL in case of error