Windows shared library generates linkage warnings

[uilianries]

Hello!

First, thanks for providing this amazing project to the community!

I have some linkage warnings when building glog 0.4.0 as shared library (with gflags 2.2.0), it does not break the build, but looks suspect.

$ cmake -G "Ninja" -DCMAKE_BUILD_TYPE="Release" -DBUILD_SHARED_LIBS="ON" -DWITH_GFLAGS="ON" -DWITH_THREADS="ON"

-- The C compiler identification is MSVC 19.26.28806.0
-- The CXX compiler identification is MSVC 19.26.28806.0
-- Check for working C compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/MSVC/14.26.28801/bin/Hostx64/x64/cl.exe
-- Check for working C compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/MSVC/14.26.28801/bin/Hostx64/x64/cl.exe - works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/MSVC/14.26.28801/bin/Hostx64/x64/cl.exe
-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/MSVC/14.26.28801/bin/Hostx64/x64/cl.exe - works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Conan: called by CMake conan helper
-- Conan: called inside local cache
-- Conan: Adjusting output directories
-- Conan: Using cmake global configuration
-- Conan: Adjusting default RPATHs Conan policies
-- Conan: Adjusting language standard
-- Conan: Using autogenerated Findgflags.cmake
-- Found gflags: 2.2.0 (found suitable version "2.2.0", minimum required is "2.2.0")
-- Library gflags_nothreads found C:/Users/uilia/.conan/data/gflags/2.2.0/_/_/package/ed160c62813fa6d86d309b2f7e6e791ae96da725/Lib/gflags_nothreads.lib
-- Found: C:/Users/uilia/.conan/data/gflags/2.2.0/_/_/package/ed160c62813fa6d86d309b2f7e6e791ae96da725/Lib/gflags_nothreads.lib
-- Library shlwapi not found in package, might be system one
-- Looking for gflags namespace
-- Looking for gflags namespace - failed
-- Looking for pthread.h
-- Looking for pthread.h - not found
-- Found Threads: TRUE
-- Looking for dlfcn.h
-- Looking for dlfcn.h - not found
-- Looking for execinfo.h
-- Looking for execinfo.h - not found
-- Looking for glob.h
-- Looking for glob.h - not found
-- Looking for inttypes.h
-- Looking for inttypes.h - found
-- Looking for libunwind.h
-- Looking for libunwind.h - not found
-- Looking for memory.h
-- Looking for memory.h - found
-- Looking for pwd.h
-- Looking for pwd.h - not found
-- Looking for stdint.h
-- Looking for stdint.h - found
-- Looking for stdlib.h
-- Looking for stdlib.h - found
-- Looking for string.h
-- Looking for string.h - found
-- Looking for strings.h
-- Looking for strings.h - not found
-- Looking for sys/stat.h
-- Looking for sys/stat.h - found
-- Looking for sys/syscall.h
-- Looking for sys/syscall.h - not found
-- Looking for sys/time.h
-- Looking for sys/time.h - not found
-- Looking for sys/types.h
-- Looking for sys/types.h - found
-- Looking for sys/utsname.h
-- Looking for sys/utsname.h - not found
-- Looking for syscall.h
-- Looking for syscall.h - not found
-- Looking for syslog.h
-- Looking for syslog.h - not found
-- Looking for ucontext.h
-- Looking for ucontext.h - not found
-- Looking for unistd.h
-- Looking for unistd.h - not found
-- Looking for unwind.h
-- Looking for unwind.h - not found
-- Looking for C++ include ext/hash_map
-- Looking for C++ include ext/hash_map - not found
-- Looking for C++ include ext/hash_set
-- Looking for C++ include ext/hash_set - not found
-- Looking for C++ include ext/slist
-- Looking for C++ include ext/slist - not found
-- Looking for C++ include tr1/unordered_map
-- Looking for C++ include tr1/unordered_map - not found
-- Looking for C++ include tr1/unordered_set
-- Looking for C++ include tr1/unordered_set - not found
-- Looking for C++ include unordered_map
-- Looking for C++ include unordered_map - found
-- Looking for C++ include unordered_set
-- Looking for C++ include unordered_set - found
-- Looking for stddef.h
-- Looking for stddef.h - found
-- Check size of unsigned __int16
-- Check size of unsigned __int16 - done
-- Check size of u_int16_t
-- Check size of u_int16_t - failed
-- Check size of uint16_t
-- Check size of uint16_t - done
-- Looking for dladdr
-- Looking for dladdr - not found
-- Looking for fcntl
-- Looking for fcntl - not found
-- Looking for pread
-- Looking for pread - not found
-- Looking for pwrite
-- Looking for pwrite - not found
-- Looking for sigaction
-- Looking for sigaction - not found
-- Looking for sigaltstack
-- Looking for sigaltstack - not found
-- Performing Test HAVE_NO_DEPRECATED
-- Performing Test HAVE_NO_DEPRECATED - Failed
-- Performing Test HAVE_NO_UNNAMED_TYPE_TEMPLATE_ARGS
-- Performing Test HAVE_NO_UNNAMED_TYPE_TEMPLATE_ARGS - Failed
-- Looking for snprintf
-- Looking for snprintf - found
-- Looking for get_static_proc_name in unwind
-- Looking for get_static_proc_name in unwind - not found
-- Looking for UnDecorateSymbolName in dbghelp
-- Looking for UnDecorateSymbolName in dbghelp - found
-- Performing Test HAVE___ATTRIBUTE__
-- Performing Test HAVE___ATTRIBUTE__ - Failed
-- Performing Test HAVE___ATTRIBUTE__VISIBILITY_DEFAULT
-- Performing Test HAVE___ATTRIBUTE__VISIBILITY_DEFAULT - Failed
-- Performing Test HAVE___ATTRIBUTE__VISIBILITY_HIDDEN
-- Performing Test HAVE___ATTRIBUTE__VISIBILITY_HIDDEN - Failed
-- Performing Test HAVE___BUILTIN_EXPECT
-- Performing Test HAVE___BUILTIN_EXPECT - Failed
-- Performing Test HAVE___SYNC_VAL_COMPARE_AND_SWAP
-- Performing Test HAVE___SYNC_VAL_COMPARE_AND_SWAP - Failed
-- Performing Test HAVE_RWLOCK
-- Performing Test HAVE_RWLOCK - Failed
-- Performing Test HAVE___DECLSPEC
-- Performing Test HAVE___DECLSPEC - Success
-- Performing Test STL_NO_NAMESPACE
-- Performing Test STL_NO_NAMESPACE - Failed
-- Performing Test STL_STD_NAMESPACE
-- Performing Test STL_STD_NAMESPACE - Success
-- Performing Test HAVE_USING_OPERATOR
-- Performing Test HAVE_USING_OPERATOR - Success
-- Performing Test HAVE_NAMESPACES
-- Performing Test HAVE_NAMESPACES - Success
-- Performing Test HAVE_GCC_TLS
-- Performing Test HAVE_GCC_TLS - Failed
-- Performing Test HAVE_MSVC_TLS
-- Performing Test HAVE_MSVC_TLS - Success
-- Performing Test HAVE_CXX11_TLS
-- Performing Test HAVE_CXX11_TLS - Success
-- Performing Test HAVE_ALIGNED_STORAGE
-- Performing Test HAVE_ALIGNED_STORAGE - Success
-- Performing Test HAVE_SYMBOLIZE
-- Performing Test HAVE_SYMBOLIZE - Success
-- Performing Test HAVE_LOCALTIME_R
-- Performing Test HAVE_LOCALTIME_R - Failed
-- Configuring done
-- Generating done
-- Build files have been written to: C:/Users/uilia/dev/glog/0.4.0/build/
**********************************************************************
** Visual Studio 2019 Developer Command Prompt v16.6.2
** Copyright (c) 2020 Microsoft Corporation
**********************************************************************
[vcvarsall.bat] Environment initialized for: 'x64'

----Running------
> cmake --build C:/Users/uilia/dev/glog/0.4.0/build -- -j12
-----------------
[1/9] Building CXX object CMakeFiles\glog.dir\src\windows\port.cc.obj

[2/9] Building CXX object CMakeFiles\glog.dir\src\raw_logging.cc.obj

[3/9] Building CXX object CMakeFiles\glog.dir\src\symbolize.cc.obj

[4/9] Building CXX object CMakeFiles\glog.dir\src\signalhandler.cc.obj

[5/9] Building CXX object CMakeFiles\glog.dir\src\demangle.cc.obj

[6/9] Building CXX object CMakeFiles\glog.dir\src\vlog_is_on.cc.obj

src\vlog_is_on.cc(53): warning C4273: 'fLI::FLAGS_v': inconsistent dll linkage
glog/logging.h(371): note: see previous definition of 'FLAGS_v'
[7/9] Building CXX object CMakeFiles\glog.dir\src\utilities.cc.obj

[8/9] Building CXX object CMakeFiles\glog.dir\src\logging.cc.obj

src\logging.cc(107): warning C4273: 'fLB::FLAGS_logtostderr': inconsistent dll linkage
glog/logging.h(334): note: see previous definition of 'FLAGS_logtostderr'
src\logging.cc(109): warning C4273: 'fLB::FLAGS_alsologtostderr': inconsistent dll linkage
glog/logging.h(337): note: see previous definition of 'FLAGS_alsologtostderr'
src\logging.cc(111): warning C4273: 'fLB::FLAGS_colorlogtostderr': inconsistent dll linkage
glog/logging.h(340): note: see previous definition of 'FLAGS_colorlogtostderr'
src\logging.cc(127): warning C4273: 'fLI::FLAGS_stderrthreshold': inconsistent dll linkage
glog/logging.h(344): note: see previous definition of 'FLAGS_stderrthreshold'
src\logging.cc(133): warning C4273: 'fLB::FLAGS_log_prefix': inconsistent dll linkage
glog/logging.h(347): note: see previous definition of 'FLAGS_log_prefix'
src\logging.cc(135): warning C4273: 'fLI::FLAGS_minloglevel': inconsistent dll linkage
glog/logging.h(358): note: see previous definition of 'FLAGS_minloglevel'
src\logging.cc(139): warning C4273: 'fLI::FLAGS_logbuflevel': inconsistent dll linkage
glog/logging.h(351): note: see previous definition of 'FLAGS_logbuflevel'
src\logging.cc(141): warning C4273: 'fLI::FLAGS_logbufsecs': inconsistent dll linkage
glog/logging.h(354): note: see previous definition of 'FLAGS_logbufsecs'
src\logging.cc(163): warning C4273: 'fLI::FLAGS_logfile_mode': inconsistent dll linkage
glog/logging.h(365): note: see previous definition of 'FLAGS_logfile_mode'
src\logging.cc(167): warning C4273: 'fLS::FLAGS_log_dir': inconsistent dll linkage
glog/logging.h(362): note: see previous definition of 'FLAGS_log_dir'
src\logging.cc(169): warning C4273: 'fLS::FLAGS_log_link': inconsistent dll linkage
glog/logging.h(369): note: see previous definition of 'FLAGS_log_link'
src\logging.cc(173): warning C4273: 'fLI::FLAGS_max_log_size': inconsistent dll linkage
glog/logging.h(374): note: see previous definition of 'FLAGS_max_log_size'
src\logging.cc(176): warning C4273: 'fLB::FLAGS_stop_logging_if_full_disk': inconsistent dll linkage
glog/logging.h(377): note: see previous definition of 'FLAGS_stop_logging_if_full_disk'
[9/9] Linking CXX shared library bin\glog.dll

   Creating library lib\glog.lib and object lib\glog.exp

LINK : warning LNK4217: symbol '?FLAGS_v@fLI@@3HA (int fLI::FLAGS_v)' defined in 'vlog_is_on.cc.obj' is imported by 'logging.cc.obj' in function '"bool __cdecl google::SendEmailInternal(char const *,char const *,char const *,bool)" (?SendEmailInternal@google@@YA_NPEBD00_N@Z)'

LINK : warning LNK4217: symbol '?FLAGS_logtostderr@fLB@@3_NA (bool fLB::FLAGS_logtostderr)' defined in 'logging.cc.obj' is imported by 'raw_logging.cc.obj' in function '"void __cdecl google::RawLog__(int,char const *,int,char const *,...)" (?RawLog__@google@@YAXHPEBDH0ZZ)'

LINK : warning LNK4217: symbol '?FLAGS_alsologtostderr@fLB@@3_NA (bool fLB::FLAGS_alsologtostderr)' defined in 'logging.cc.obj' is imported by 'raw_logging.cc.obj' in function '"void __cdecl google::RawLog__(int,char const *,int,char const *,...)" (?RawLog__@google@@YAXHPEBDH0ZZ)'

LINK : warning LNK4217: symbol '?FLAGS_stderrthreshold@fLI@@3HA (int fLI::FLAGS_stderrthreshold)' defined in 'logging.cc.obj' is imported by 'raw_logging.cc.obj' in function '"void __cdecl google::RawLog__(int,char const *,int,char const *,...)" (?RawLog__@google@@YAXHPEBDH0ZZ)'


$ cmake --build C:\Users\uilia\dev\glog\0.4.0\build --target install -- -j12

[0/1] Install the project...

-- Install configuration: "Release"
-- Installing: C:/Users/uilia/dev\glog\0.4.0\build/lib/glog.lib
-- Installing: C:/Users/uilia/dev\glog\0.4.0\build/bin/glog.dll
-- Installing: C:/Users/uilia/dev\glog\0.4.0\build/include/glog/logging.h
-- Installing: C:/Users/uilia/dev\glog\0.4.0\build/include/glog/raw_logging.h
-- Installing: C:/Users/uilia/dev\glog\0.4.0\build/include/glog/stl_logging.h
-- Installing: C:/Users/uilia/dev\glog\0.4.0\build/include/glog/vlog_is_on.h
-- Installing: C:/Users/uilia/dev\glog\0.4.0\build/include/glog/log_severity.h
-- Installing: C:/Users/uilia/dev\glog\0.4.0\build/lib/cmake/glog/glog-config.cmake
-- Installing: C:/Users/uilia/dev\glog\0.4.0\build/lib/cmake/glog/glog-config-version.cmake
-- Installing: C:/Users/uilia/dev\glog\0.4.0\build/lib/cmake/glog/glog-targets.cmake
-- Installing: C:/Users/uilia/dev\glog\0.4.0\build/lib/cmake/glog/glog-targets-release.cmake

Environment:

arch=x86_64
build_type=Release
compiler=Visual Studio
compiler.runtime=MD
compiler.version=16
os=Windows
os.version=10

Do you think this is a problem?

[camnv93]

have you fixed this issue yet? I also got this error

[kumarchandresh]

I don't think it is a problem. Looking at the source code, I can see that glog can work with both gflags options and GLOG_* env variables, that's why it has two definitions for each option, one is implemented in glog and other is promised from gflags, if required (note that this is managed internally by glog). I don't know if it's okay to have such Level 1 warnings or not, but I'm not educated enough to do anything about it.

This is from src/base/commandlineflag.h, Line 105:110

// Define GLOG_DEFINE_* using DEFINE_* . By using these macros, we
// have GLOG_* environ variables even if we have gflags installed.
//
// If both an environment variable and a flag are specified, the value
// specified by a flag wins. E.g., if GLOG_v=0 and --v=1, the
// verbosity will be 1, not 0.

This stackoverflow answer elaborates it well if you wanna read more about it.