diff -Naur syslinux/mk/efi.mk syslinux.new/mk/efi.mk
--- syslinux/mk/efi.mk	2022-02-08 08:32:30.683508231 +0100
+++ syslinux.new/mk/efi.mk	2022-02-08 08:35:06.695618667 +0100
@@ -8,6 +8,7 @@
 # gnuefi sets up architecture specifics in ia32 or x86_64 sub directories
 # set up the LIBDIR and EFIINC for building for the appropriate architecture
 GCCOPT := $(call gcc_ok,-fno-stack-protector,)
+GCCOPT += $(call gcc_ok,-fcommon)
 EFIINC = $(objdir)/include/efi
 LIBDIR  = $(objdir)/lib
 
diff -Naur syslinux/mk/elf.mk syslinux.new/mk/elf.mk
--- syslinux/mk/elf.mk	2022-02-08 08:32:30.683508231 +0100
+++ syslinux.new/mk/elf.mk	2022-02-08 08:35:23.571738788 +0100
@@ -42,6 +42,7 @@
 GCCOPT += $(call gcc_ok,-falign-jumps=0,-malign-jumps=0)
 GCCOPT += $(call gcc_ok,-falign-labels=0,-malign-labels=0)
 GCCOPT += $(call gcc_ok,-falign-loops=0,-malign-loops=0)
+GCCOPT += $(call gcc_ok,-fcommon)
 
 com32 = $(topdir)/com32
 core = $(topdir)/core
diff -Naur syslinux/mk/embedded.mk syslinux.new/mk/embedded.mk
--- syslinux/mk/embedded.mk	2022-02-08 08:32:30.683508231 +0100
+++ syslinux.new/mk/embedded.mk	2022-02-08 08:36:10.282071294 +0100
@@ -51,6 +51,7 @@
 GCCOPT    += $(call gcc_ok,-falign-labels=0,-malign-labels=0)
 GCCOPT    += $(call gcc_ok,-falign-loops=0,-malign-loops=0)
 GCCOPT    += $(call gcc_ok,-fvisibility=hidden)
+GCCOPT 	  += $(call gcc_ok,-fcommon)
 
 LIBGCC    := $(shell $(CC) $(GCCOPT) --print-libgcc)
 
diff -Naur syslinux/mk/lib.mk syslinux.new/mk/lib.mk
--- syslinux/mk/lib.mk	2022-02-08 08:32:30.683508231 +0100
+++ syslinux.new/mk/lib.mk	2022-02-08 08:36:21.394150396 +0100
@@ -28,6 +28,7 @@
 GCCOPT += $(call gcc_ok,-falign-jumps=0,-malign-jumps=0)
 GCCOPT += $(call gcc_ok,-falign-labels=0,-malign-labels=0)
 GCCOPT += $(call gcc_ok,-falign-loops=0,-malign-loops=0)
+GCCOPT += $(call gcc_ok,-fcommon)
 
 INCLUDE	= -I$(SRC)
 STRIP	= strip --strip-all -R .comment -R .note
--- syslinux/dos/string.h	2022-02-08 14:42:52.654027015 +0100
+++ syslinux.new/dos/string.h	2022-02-08 14:44:36.932776621 +0100
@@ -5,12 +5,21 @@
 #ifndef _STRING_H
 #define _STRING_H
 
+#include <stddef.h>
+
 /* Standard routines */
 #define memcpy(a,b,c)	__builtin_memcpy(a,b,c)
 #define memmove(a,b,c)	__builtin_memmove(a,b,c)
 #define memset(a,b,c)	__builtin_memset(a,b,c)
 #define strcpy(a,b)	__builtin_strcpy(a,b)
-#define strlen(a)	__builtin_strlen(a)
+
+static inline size_t strlen(const char *s)
+{
+	const char *ss = s;
+	while (*ss)
+		ss++;
+	return ss - s;
+}
 
 /* This only returns true or false */
 static inline int memcmp(const void *__m1, const void *__m2, unsigned int __n)