From 05c67589851c70df19a94d5a00b6634681f08bcd Mon Sep 17 00:00:00 2001
From: Nik Konyuchenko <spaun2002mobile@gmail.com>
Date: Thu, 24 Jun 2021 00:51:21 -0700
Subject: Fix build of older Glibc using GCC >=10

Issue #1535

GCC 10 changed the default to -fno-common, which leads to a linking error in GLibc older than 2.30.

This change adds -fcommon cflag for the target GLibc versions <=2.29 and GCC >=10.

This change also adds additional cflags for the target GLibc to disable
new GCC11 checks that lead to compilation errors.

Signed-off-by: Nik Konyuchenko <spaun2002mobile@gmail.com>

diff --git a/config/libc/glibc.in b/config/libc/glibc.in
index 5a3b1b8..b2cf0da 100644
--- a/config/libc/glibc.in
+++ b/config/libc/glibc.in
@@ -181,6 +181,7 @@ config GLIBC_CONFIGPARMS
 config GLIBC_EXTRA_CFLAGS
     string
     prompt "extra target CFLAGS"
+    default "-Wno-missing-attributes -Wno-array-bounds -Wno-array-parameter -Wno-stringop-overflow -Wno-maybe-uninitialized" if GLIBC_2_29_or_older && GCC_11_or_later
     default ""
     help
       Extra target CFLAGS to use when building.
@@ -416,4 +417,10 @@ config GLIBC_ENABLE_WERROR
 
 endif
 
+config GLIBC_ENABLE_COMMON_FLAG
+    bool "Enable -fcommon flag for older version of glibc when using GCC >=10"
+    default y if GLIBC_2_29_or_older && GCC_10_or_later
+    default n if GLIBC_2_30_or_later || GCC_9_or_older
+
+
 endif # KERNEL_LINUX
diff --git a/scripts/build/libc/glibc.sh b/scripts/build/libc/glibc.sh
index ba6e548..0db7c1c 100644
--- a/scripts/build/libc/glibc.sh
+++ b/scripts/build/libc/glibc.sh
@@ -201,6 +201,10 @@ glibc_backend_once()
     # glibc can't be built without -O2 (reference needed!)
     glibc_cflags+=" -g -O2"
 
+    if [ "${CT_GLIBC_ENABLE_COMMON_FLAG}" = "y" ]; then
+        glibc_cflags+=" -fcommon"
+    fi
+
     case "${CT_GLIBC_ENABLE_FORTIFIED_BUILD}" in
         y)  ;;
         *)  glibc_cflags+=" -U_FORTIFY_SOURCE";;
-- 
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