编译base/TimeZone.cc与base/tests/TimeZone_util.cc时报错，添加-Wno-conversion与-Wno-missing-field-initializers后编译成功

[Eresh-tech]

Linux distro and version? x86 or ARM? 32-bit or 64-bit?

Linux version 3.10.0-1160.el7.x86_64

Branch (cpp98/cpp11/cpp17) and version of muduo?

cpp11
v2.0.2

Version of cmake, gcc and boost? (If not from distro.)

cmake version 2.8.12.2
gcc: 首先使用gcc-4.8.5-44，首次编译失败后切换至11.2.1，以下报错信息均在11.2.1下出现
boost: 1.53.0-28

报错信息：

[ 0%] Building CXX object muduo/base/CMakeFiles/muduo_base.dir/TimeZone.cc.o
muduo/muduo/base/TimeZone.cc: 在函数‘bool muduo::detail::readDataBlock(muduo::detail::File&, muduo::TimeZone::Data*, bool)’中:
muduo/muduo/base/TimeZone.cc:171:36: 错误：‘int’转换自‘long unsigned int’时可能改变值 [-Werror=conversion]
const int time_size = v1 ? sizeof(int32_t) : sizeof(int64_t);
^
muduo/muduo/base/TimeZone.cc:171:54: 错误：‘int’转换自‘long unsigned int’时可能改变值 [-Werror=conversion]
const int time_size = v1 ? sizeof(int32_t) : sizeof(int64_t);
^
cc1plus: all warnings being treated as errors
make[2]: *** [muduo/base/CMakeFiles/muduo_base.dir/build.make:381：muduo/base/CMakeFiles/muduo_base.dir/TimeZone.cc.o] 错误 1

添加-Wno-conversion后报错信息如下：
muduo/muduo/base/tests/TimeZone_util.cc: 在函数‘int main(int, char**)’中:
muduo/muduo/base/tests/TimeZone_util.cc:47:24: 错误：成员‘tm::tm_sec’缺少初始值设定 [-Werror=missing-field-initializers]
struct tm tm = { };
^
muduo/muduo/base/tests/TimeZone_util.cc:47:24: 错误：成员‘tm::tm_min’缺少初始值设定 [-Werror=missing-field-initializers]
muduo/muduo/base/tests/TimeZone_util.cc:47:24: 错误：成员‘tm::tm_hour’缺少初始值设定 [-Werror=missing-field-initializers]
muduo/muduo/base/tests/TimeZone_util.cc:47:24: 错误：成员‘tm::tm_mday’缺少初始值设定 [-Werror=missing-field-initializers]
muduo/muduo/base/tests/TimeZone_util.cc:47:24: 错误：成员‘tm::tm_mon’缺少初始值设定 [-Werror=missing-field-initializers]
muduo/muduo/base/tests/TimeZone_util.cc:47:24: 错误：成员‘tm::tm_year’缺少初始值设定 [-Werror=missing-field-initializers]
muduo/muduo/base/tests/TimeZone_util.cc:47:24: 错误：成员‘tm::tm_wday’缺少初始值设定 [-Werror=missing-field-initializers]
muduo/muduo/base/tests/TimeZone_util.cc:47:24: 错误：成员‘tm::tm_yday’缺少初始值设定 [-Werror=missing-field-initializers]
muduo/muduo/base/tests/TimeZone_util.cc:47:24: 错误：成员‘tm::tm_isdst’缺少初始值设定 [-Werror=missing-field-initializers]
muduo/muduo/base/tests/TimeZone_util.cc:47:24: 错误：成员‘tm::tm_gmtoff’缺少初始值设定 [-Werror=missing-field-initializers]
muduo/muduo/base/tests/TimeZone_util.cc:47:24: 错误：成员‘tm::tm_zone’缺少初始值设定 [-Werror=missing-field-initializers]
cc1plus: all warnings being treated as errors

我尝试修改muduo/base/CMakeLists.txt， 添加-Wno-conversion与-Wno-missing-field-initializers后编译成功

[chenxuanw]

我这样build成功