diff -u lessfs-1.7.0/lib_cfg.c lessfs-1.7.0-gcc10/lib_cfg.c
--- lessfs-1.7.0/lib_cfg.c	2011-09-30 20:13:08.000000000 +0200
+++ lessfs-1.7.0-gcc10/lib_cfg.c	2021-10-17 21:12:40.750623419 +0200
@@ -34,6 +34,8 @@
 #include "lib_str.h"
 #include "retcodes.h"
 
+struct configdata *config;
+
 int r_env_cfg(char *configfile)
 {
     FILE *config;
diff -u lessfs-1.7.0/lib_cfg.h lessfs-1.7.0-gcc10/lib_cfg.h
--- lessfs-1.7.0/lib_cfg.h	2012-04-21 18:09:54.000000000 +0200
+++ lessfs-1.7.0-gcc10/lib_cfg.h	2021-10-17 21:12:31.999872984 +0200
@@ -88,7 +88,7 @@
 // Counter is increase by normal ops, decreased by truncation.
 // (background) Truncation will therefore become slower when other tasks are running.
 };
-struct configdata *config;
+extern struct configdata *config;
 
 int read_s_cfg(char *cfgfile, char *value, int size);
 int read_m_cfg(char *cfgfile, char *value, char *value2, int size);
diff -u lessfs-1.7.0/lib_tc.c lessfs-1.7.0-gcc10/lib_tc.c
--- lessfs-1.7.0/lib_tc.c	2013-11-16 05:09:05.000000000 +0100
+++ lessfs-1.7.0-gcc10/lib_tc.c	2021-10-17 21:15:33.016360983 +0200
@@ -74,14 +74,14 @@
 extern int max_threads;
 extern char *passwd;
 
-TCHDB *dbb;
-TCHDB *dbu;
-TCHDB *dbp;
-TCBDB *dbl;
-TCHDB *dbs;
-TCHDB *dbdta;
-TCBDB *dbdirent;
-TCBDB *freelist;
+extern TCHDB *dbb;
+extern TCHDB *dbu;
+extern TCHDB *dbp;
+extern TCBDB *dbl;
+extern TCHDB *dbs;
+extern TCHDB *dbdta;
+extern TCBDB *dbdirent;
+extern TCBDB *freelist;
 
 extern TCTREE *workqtree;       // Used to buffer incoming data (writes) 
 extern TCTREE *readcachetree;   // Used to cache chunks of data that are likely to be read
@@ -96,9 +96,9 @@
 extern unsigned long long nextoffset;
 int written = 0;
 
-const char *offset_lockedby;
+extern const char *offset_lockedby;
 
-u_int32_t db_flags, env_flags;
+extern u_int32_t db_flags, env_flags;
 
 int btree_test_transaction(TCBDB * bdb)
 {