--- com32/MCONFIG	2011-04-18 23:24:17.000000000 +0200

+++ com32/MCONFIG	2020-03-18 17:05:57.507347671 +0100

@@ -18,6 +18,7 @@

 include $(topdir)/MCONFIG

 GCCOPT := $(call gcc_ok,-std=gnu99,)

+GCCOPT += $(call gcc_ok,-fcommon,)

 GCCOPT += $(call gcc_ok,-m32,)

 GCCOPT += $(call gcc_ok,-fno-stack-protector,)

 GCCOPT += $(call gcc_ok,-fwrapv,)

--- com32/lib/MCONFIG	2011-04-18 23:24:17.000000000 +0200

+++ com32/lib/MCONFIG	2020-03-18 17:07:39.960337684 +0100

@@ -3,6 +3,7 @@

 include $(topdir)/MCONFIG

 GCCOPT := $(call gcc_ok,-std=gnu99,)

+GCCOPT += $(call gcc_ok,-fcommon,)

 GCCOPT += $(call gcc_ok,-m32,)

 GCCOPT += $(call gcc_ok,-fno-stack-protector,)

 GCCOPT += $(call gcc_ok,-fwrapv,)

--- dos/errno.h	2011-04-18 23:24:17.000000000 +0200

+++ dos/errno.h	2020-03-18 17:12:17.359044057 +0100

@@ -36,7 +36,7 @@

 #define	EDOM		33	/* Math argument out of domain of func */

 #define	ERANGE		34	/* Math result not representable */

-int errno;

+int errno __attribute__ ((common));

 void perror(const char *);

 #endif /* ERRNO_H */

--- gpxe/src/core/exec.c	2011-04-18 23:24:17.000000000 +0200

+++ gpxe/src/core/exec.c	2020-03-18 16:56:52.257888015 +0100

@@ -38,8 +38,8 @@

  */

 /* Avoid dragging in getopt.o unless a command really uses it */

-int optind;

-int nextchar;

+extern int optind;

+extern int nextchar;

 /**

  * Execute command

--- gpxe/src/include/compiler.h	2011-04-18 23:24:17.000000000 +0200

+++ gpxe/src/include/compiler.h	2020-03-18 16:48:56.193236495 +0100

@@ -64,7 +64,7 @@

    .comm	_sym, 0

 #else /* ASSEMBLY */

 #define PROVIDE_SYMBOL( _sym )				\

-	char _sym[0]

+	char _sym[0] __attribute__ ((common))

 #endif /* ASSEMBLY */

 /** Require a symbol within this object file

--- dos/string.h	2020-03-18 17:25:50.019155261 +0100

+++ dos/string.h	2020-03-19 15:10:36.310787373 +0100

@@ -5,12 +5,13 @@

 #ifndef _STRING_H

 #define _STRING_H

+#include <stdlib.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)

 /* This only returns true or false */

 static inline int memcmp(const void *__m1, const void *__m2, unsigned int __n)

@@ -21,6 +22,15 @@

     return rv;

 }

+static inline size_t strlen(const char *s)

+{

+  size_t len = 0;

+

+  while(*s++) len++;

+

+  return len;

+}

+

 extern char *strchr(const char *s, int c);

 #endif /* _STRING_H */