File 0019-gcc-10-compatibility.patch of Package syslinux

From: Lukas Schwaighofer <lukas@schwaighofer.name>
Date: Sun, 16 Aug 2020 15:23:21 +0200
Subject: GCC-10 compatibility patch

* Add `-fcommon` to most gcc invocations to allow duplicate definitions
* __builtin_strlen is not really a "builtin" an implementation still
  needs to be provided (source:
  https://bugzilla.suse.com/show_bug.cgi?id=1166605#c5). Work around the
  issue by supplying an inline function. The strlen function added to
  dos/string.h was copied from com32/lib/strlen.c.
---
 dos/string.h   | 11 ++++++++++-
 mk/efi.mk      |  1 +
 mk/elf.mk      |  1 +
 mk/embedded.mk |  2 +-
 mk/lib.mk      |  2 +-
 5 files changed, 14 insertions(+), 3 deletions(-)

Index: b/dos/string.h
===================================================================
--- a/dos/string.h
+++ b/dos/string.h
@@ -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)
Index: b/mk/efi.mk
===================================================================
--- a/mk/efi.mk
+++ b/mk/efi.mk
@@ -25,6 +25,7 @@ FORMAT=efi-app-$(EFI_SUBARCH)
 
 CFLAGS = -I$(EFIINC) -I$(EFIINC)/$(EFI_SUBARCH) \
 		-DEFI_FUNCTION_WRAPPER -fPIC -fshort-wchar -ffreestanding \
+		-fcommon \
 		-Wall -I$(com32)/include -I$(com32)/include/sys \
 		-I$(core)/include -I$(core)/ $(ARCHOPT) \
 		-I$(com32)/lib/ -I$(com32)/libutil/include -std=gnu99 \
Index: b/mk/elf.mk
===================================================================
--- a/mk/elf.mk
+++ b/mk/elf.mk
@@ -55,6 +55,7 @@ GPLINCLUDE =
 endif
 
 CFLAGS     = $(GCCOPT) $(GCCWARN) -W -Wall \
+	     -fcommon \
 	     -fomit-frame-pointer -D__COM32__ -D__FIRMWARE_$(FIRMWARE)__ -DDYNAMIC_MODULE \
 	     -nostdinc -iwithprefix include \
 	     -I$(com32)/libutil/include -I$(com32)/include \
Index: b/mk/embedded.mk
===================================================================
--- a/mk/embedded.mk
+++ b/mk/embedded.mk
@@ -57,7 +57,7 @@ LIBGCC    := $(shell $(CC) $(GCCOPT) --p
 LD        += -m elf_$(ARCH)
 
 # Note: use += for CFLAGS and SFLAGS in case something is set in MCONFIG.local
-CFLAGS    += $(GCCOPT) -g $(GCCWARN) -Wno-sign-compare $(OPTFLAGS) $(INCLUDES)
+CFLAGS    += $(GCCOPT) -g $(GCCWARN) -Wno-sign-compare -fcommon $(OPTFLAGS) $(INCLUDES)
 SFLAGS    += $(CFLAGS) -D__ASSEMBLY__
 
 .SUFFIXES: .c .o .S .s .i .elf .com .bin .asm .lst .c32 .lss
Index: b/mk/lib.mk
===================================================================
--- a/mk/lib.mk
+++ b/mk/lib.mk
@@ -49,7 +49,7 @@ OPTFLAGS  = -Os -march=$(MARCH) -falign-
 	    -falign-labels=0 -ffast-math -fomit-frame-pointer
 WARNFLAGS = $(GCCWARN) -Wpointer-arith -Wwrite-strings -Wstrict-prototypes -Winline
 
-CFLAGS  = $(OPTFLAGS) $(REQFLAGS) $(WARNFLAGS) $(LIBFLAGS)
+CFLAGS  = $(OPTFLAGS) $(REQFLAGS) -fcommon $(WARNFLAGS) $(LIBFLAGS)
 
 ifeq ($(FWCLASS),EFI)
 CFLAGS += -mno-red-zone