LNK2001 error when building dynamic library which call win32 GUID `operator==`

Question

Follow code is unable to build when target is dynamic library.

// test.cpp
#include <mfapi.h>

bool CompareGUID() {
    GUID a;
    GUID b;
    return a == b;
}

# CMakeLists.txt
cmake_minimum_required(VERSION 3.6)
project (Demo)

# c++11
set(CMAKE_CXX_STANDARD 14)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS OFF)

set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS TRUE)

# target
add_library (lib test.cpp)

add_executable (main main.cpp)

target_link_libraries(main lib)

compile output:

➜  build Import-VisualStudioVars 2017 -Architecture x86
**********************************************************************
** Visual Studio 2017 Developer Command Prompt v15.9.50
** Copyright (c) 2017 Microsoft Corporation
**********************************************************************
[vcvarsall.bat] Environment initialized for: 'x86'
➜  build cmake .. -G "Ninja" -DBUILD_SHARED_LIBS=OFF
-- The C compiler identification is MSVC 19.16.27048.0
-- The CXX compiler identification is MSVC 19.16.27048.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: C:/Program Files (x86)/Microsoft Visual Studio/2017/Community/VC/Tools/MSVC/14.16.27023/bin/Hostx86/x86/cl.exe - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio/2017/Community/VC/Tools/MSVC/14.16.27023/bin/Hostx86/x86/cl.exe - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: D:/Repos/misc/TestMfDynamic/build
➜  build ninja
[4/4] Linking CXX executable main.exe
➜  build cmake .. -G "Ninja" -DBUILD_SHARED_LIBS=ON
-- Configuring done
-- Generating done
-- Build files have been written to: D:/Repos/misc/TestMfDynamic/build
➜  build ninja
[2/3] Linking CXX shared library lib.dll
FAILED: lib.dll lib.lib
cmd.exe /C "cmd.exe /C "C:\Users\zgzf1\scoop\apps\cmake\3.24.0\bin\cmake.exe -E __create_def D:\Repos\misc\TestMfDynamic\build\CMakeFiles\lib.dir\.\exports.def D:\Repos\misc\TestMfDynamic\build\CMakeFiles\lib.dir\.\exports.def.objs && cd D:\Repos\misc\TestMfDynamic\build" && C:\Users\zgzf1\scoop\apps\cmake\3.24.0\bin\cmake.exe -E vs_link_dll --intdir=CMakeFiles\lib.dir --rc=C:\PROGRA~2\WI3CF2~1\10\bin\100226~1.0\x86\rc.exe --mt=C:\PROGRA~2\WI3CF2~1\10\bin\100226~1.0\x86\mt.exe --manifests  -- C:\PROGRA~2\MICROS~2\2017\COMMUN~1\VC\Tools\MSVC\1416~1.270\bin\Hostx86\x86\link.exe /nologo CMakeFiles\lib.dir\test.cpp.obj  /out:lib.dll /implib:lib.lib /pdb:lib.pdb /dll /version:0.0 /machine:X86 /debug /INCREMENTAL  /DEF:CMakeFiles\lib.dir\.\exports.def  kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib  && cd ."
LINK Pass 1: command "C:\PROGRA~2\MICROS~2\2017\COMMUN~1\VC\Tools\MSVC\1416~1.270\bin\Hostx86\x86\link.exe /nologo CMakeFiles\lib.dir\test.cpp.obj /out:lib.dll /implib:lib.lib /pdb:lib.pdb /dll /version:0.0 /machine:X86 /debug /INCREMENTAL /DEF:CMakeFiles\lib.dir\.\exports.def kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib /MANIFEST /MANIFESTFILE:CMakeFiles\lib.dir/intermediate.manifest CMakeFiles\lib.dir/manifest.res" failed (exit code 1120) with the following output:
exports.def : error LNK2001:
lib.lib : fatal error LNK1120: 1
ninja: build stopped: subcommand failed.

However, It is ok when build static library and linked by executable program.

I found two way to fix this problem.

• Change the include header mfapi.h to guiddef.h.
• Change == to IsEqualGUID.

But I still do not no why. I try to figure out by compare assembly code(https://godbolt.org/z/GfW1EExf6 and https://godbolt.org/z/4xMjdEeca). The only difference is

call    bool operator==(_GUID const &,_GUID const &)

and

call    ==

I can not explain this problem. Is there any more detailed explanation？Any reply will be appreciated。