/**********************************************************************
* elfutils cc1: all warnings being treated as errors
* 说明：
* 在Ubuntu 18.04上编译Yocto，elfutils的Makefile中出现没有识别到一些配置，
* 需要在Makefile中去掉-Werror选项。
*
* 2018-6-14 深圳 宝安西乡 曾剑锋
*********************************************************************/
一、参考文档：
1. How to compile without warnings being treated as errors?
https://stackoverflow.com/questions/11561261/how-to-compile-without-warnings-being-treated-as-errors
2. all warnings being treated as errors
https://wizardforcel.gitbooks.io/100-gcc-tips/content/warnings-treated-as-errors.html
二、报错现象：
1. 现象：
x86_64-linux/usr/include -O2 -pipe -c -o dwfl_report_elf.o ../../elfutils-0.164/libdwfl/dwfl_report_elf.c
| ../../elfutils-0.164/libdwfl/dwfl_report_elf.c: In function '__libdwfl_elf_address_range':
| ../../elfutils-0.164/libdwfl/dwfl_report_elf.c:172:19: error: this statement may fall through [-Werror=implicit-fallthrough=]
| add_p_vaddr = true;
| ^
| ../../elfutils-0.164/libdwfl/dwfl_report_elf.c:174:5: note: here
| case ET_DYN:
| ^~~~
| cc1: all warnings being treated as errors
| Makefile:576: recipe for target 'dwfl_report_elf.o' failed
2. 现象：
imx6q-x11/tmp/sysroots/x86_64-linux/usr/include -O2 -pipe -c -o dwarf_next_cfi.o ../../elfutils-0.164/libdw/dwarf_next_cfi.c
| In file included from ../../elfutils-0.164/libdw/dwarf_next_cfi.c:34:0:
| ../../elfutils-0.164/libdw/encoded-value.h: In function 'encoded_value_size':
| ../../elfutils-0.164/libdw/encoded-value.h:60:10: error: this statement may fall through [-Werror=implicit-fallthrough=]
| if (p != NULL)
| ^
| ../../elfutils-0.164/libdw/encoded-value.h:68:5: note: here
| default:
| ^~~~~~~
| cc1: all warnings being treated as errors
| Makefile:708: recipe for target 'dwarf_next_cfi.o' failed
| make[3]: *** [dwarf_next_cfi.o] Error 1
3. 现象：
inux/usr/include -O2 -pipe -c -o i386_disasm.o ../../elfutils-0.164/libcpu/i386_disasm.c
| ../../elfutils-0.164/libcpu/i386_disasm.c: In function 'i386_disasm':
| ../../elfutils-0.164/libcpu/i386_disasm.c:789:9: error: this statement may fall through [-Werror=implicit-fallthrough=]
| if (data[1] == 0xc2)
| ^
| ../../elfutils-0.164/libcpu/i386_disasm.c:823:4: note: here
| default:
| ^~~~~~~
| cc1: all warnings being treated as errors
| Makefile:441: recipe for target 'i386_disasm.o' failed
三、解决方法：
1. 原因： cc1: all warnings being treated as errors
2. 修改对应的Makefile，去掉-Werror：
3. 手动处理示例：
/home/zengjf/zengjf/fsl-release-bsp/imx6q-x11/tmp/work/x86_64-linux/elfutils-native/0.164-r0/build/libdwfl/Makefile
[...省略]
# Warn about stack usage of more than 256K = 262144 bytes.
STACK_USAGE_WARNING = -Wstack-usage=262144
AM_CFLAGS = -std=gnu99 -Wall -Wshadow -Wformat=2 \
-Wold-style-definition -Wstrict-prototypes \
$(if $($(*F)_no_Werror),,-Werror) \ # remove this line
$(if $($(*F)_no_Wunused),,-Wunused -Wextra) \
$(if $($(*F)_no_Wstack_usage),,$(STACK_USAGE_WARNING)) \
$($(*F)_CFLAGS)
[...省略]
4. 获取Makefile生成信息：
zengjf@zengjf:~/zengjf/fsl-release-bsp/imx6q-x11/tmp/work/x86_64-linux/elfutils-native/0.164-r0$ grep _no_Werror * -r
build/tests/Makefile: $(if $($(*F)_no_Werror),,-Werror) \
build/libdwfl/Makefile.bak: $(if $($(*F)_no_Werror),,-Werror) \
build/backends/Makefile: $(if $($(*F)_no_Werror),,-Werror) \
build/libdwelf/Makefile: $(if $($(*F)_no_Werror),,-Werror) \
build/lib/Makefile: $($(*F)_no_Werror),,-Werror) $(if \
build/libasm/Makefile: $(if $($(*F)_no_Werror),,-Werror) \
build/libelf/Makefile: $($(*F)_no_Werror),,-Werror) $(if \
build/libebl/Makefile: $($(*F)_no_Werror),,-Werror) $(if \
build/src/Makefile: $(if $($(*F)_no_Werror),,-Werror) \
build/src/Makefile:ldlex_no_Werror = yes
build/libcpu/Makefile:i386_lex_no_Werror = yes
elfutils-0.164/tests/Makefile.in: $(if $($(*F)_no_Werror),,-Werror) \
elfutils-0.164/libdwfl/Makefile.in: $(if $($(*F)_no_Werror),,-Werror) \
elfutils-0.164/backends/Makefile.in: $(if $($(*F)_no_Werror),,-Werror) \
elfutils-0.164/config/eu.am: $(if $($(*F)_no_Werror),,-Werror) \
elfutils-0.164/libdwelf/Makefile.in: $(if $($(*F)_no_Werror),,-Werror) \
elfutils-0.164/libdw/Makefile.in: $($(*F)_no_Werror),,-Werror) $(if \
elfutils-0.164/lib/Makefile.in: $($(*F)_no_Werror),,-Werror) $(if \
elfutils-0.164/libasm/Makefile.in: $(if $($(*F)_no_Werror),,-Werror) \
elfutils-0.164/libelf/Makefile.in: $($(*F)_no_Werror),,-Werror) $(if \
elfutils-0.164/libebl/Makefile.in: $($(*F)_no_Werror),,-Werror) $(if \
elfutils-0.164/src/Makefile.in: $(if $($(*F)_no_Werror),,-Werror) \
elfutils-0.164/src/Makefile.in:ldlex_no_Werror = yes
elfutils-0.164/src/Makefile.am:ldlex_no_Werror = yes
elfutils-0.164/libcpu/Makefile.in: $($(*F)_no_Werror),,-Werror) $(if \
elfutils-0.164/libcpu/Makefile.in:i386_lex_no_Werror = yes
elfutils-0.164/libcpu/Makefile.am:i386_lex_no_Werror = yes
elfutils-0.164/.pc/dso-link-change.patch/src/Makefile.am:ldlex_no_Werror = yes
elfutils-0.164/.pc/uclibc-support.patch/libcpu/Makefile.am:i386_lex_no_Werror = yes
zengjf@zengjf:~/zengjf/fsl-release-bsp/imx6q-x11/tmp/work/x86_64-linux/elfutils-native/0.164-r0$
5. 一个一个文件修改比较麻烦，依据第4点，修改对应的yes为no就可以比较快捷的一次性全部解决问题，然而实际情况是没有识别到ldlex和i386_lex，乖乖的手动删除或者制作Shell脚本处理；
6. 自动化shell命令：
1. grep _no_Werror\) * -r | cut -d":" -f1 | xargs sed -i "s/[$](if [$]([$]([*F]*)_no_Werror),,-Werror)//"
2. grep _no_Werror\) * -r | cut -d":" -f1 | xargs sed -i "s/[$]([$]([*F]*)_no_Werror),,-Werror) [$](if//"
