[build] gui-builder build failure

[JackBoosY]

Hi guys,
We received a port bug on vcpkg (microsoft/vcpkg#18691) that report the gui-builder fail to build:

[115/116] cmd.exe /C "cd . && D:\vcpkg\downloads\tools\cmake-3.20.2-windows\cmake-3.20.2-windows-i386\bin\cmake.exe -E vs_link_exe --intdir=gui-builder\CMakeFiles\gui-builder.dir --rc=C:\PROGRA~2\WI3CF2~1\10\bin\100190~1.0\x64\rc.exe --mt=C:\PROGRA~2\WI3CF2~1\10\bin\100190~1.0\x64\mt.exe --manifests  -- C:\PROGRA~2\MICROS~2\2019\COMMUN~1\VC\Tools\MSVC\1429~1.300\bin\Hostx64\x64\link.exe  gui-builder\CMakeFiles\gui-builder.dir\src\main.cpp.obj gui-builder\CMakeFiles\gui-builder.dir\src\Form.cpp.obj gui-builder\CMakeFiles\gui-builder.dir\src\GuiBuilder.cpp.obj  /out:gui-builder\gui-builder.exe /implib:gui-builder\gui-builder.lib /pdb:gui-builder\gui-builder.pdb /version:0.0 /machine:x64 /nologo    /debug /INCREMENTAL /subsystem:windows  lib\tgui-d.lib  kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib && cmd.exe /C "cd /D D:\vcpkg\buildtrees\tgui\x64-windows-dbg\gui-builder && D:\vcpkg\downloads\tools\cmake-3.20.2-windows\cmake-3.20.2-windows-i386\bin\cmake.exe -E copy D:/vcpkg/buildtrees/tgui/x64-windows-dbg/gui-builder/gui-builder.exe D:/vcpkg/buildtrees/tgui/src/6c283daf87-fb8995dab3.clean/gui-builder/ && D:\vcpkg\downloads\tools\cmake-3.20.2-windows\cmake-3.20.2-windows-i386\bin\cmake.exe -E copy_directory D:/vcpkg/buildtrees/tgui/src/6c283daf87-fb8995dab3.clean/themes D:/vcpkg/buildtrees/tgui/src/6c283daf87-fb8995dab3.clean/gui-builder/themes""
FAILED: gui-builder/gui-builder.exe 
cmd.exe /C "cd . && D:\vcpkg\downloads\tools\cmake-3.20.2-windows\cmake-3.20.2-windows-i386\bin\cmake.exe -E vs_link_exe --intdir=gui-builder\CMakeFiles\gui-builder.dir --rc=C:\PROGRA~2\WI3CF2~1\10\bin\100190~1.0\x64\rc.exe --mt=C:\PROGRA~2\WI3CF2~1\10\bin\100190~1.0\x64\mt.exe --manifests  -- C:\PROGRA~2\MICROS~2\2019\COMMUN~1\VC\Tools\MSVC\1429~1.300\bin\Hostx64\x64\link.exe  gui-builder\CMakeFiles\gui-builder.dir\src\main.cpp.obj gui-builder\CMakeFiles\gui-builder.dir\src\Form.cpp.obj gui-builder\CMakeFiles\gui-builder.dir\src\GuiBuilder.cpp.obj  /out:gui-builder\gui-builder.exe /implib:gui-builder\gui-builder.lib /pdb:gui-builder\gui-builder.pdb /version:0.0 /machine:x64 /nologo    /debug /INCREMENTAL /subsystem:windows  lib\tgui-d.lib  kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib && cmd.exe /C "cd /D D:\vcpkg\buildtrees\tgui\x64-windows-dbg\gui-builder && D:\vcpkg\downloads\tools\cmake-3.20.2-windows\cmake-3.20.2-windows-i386\bin\cmake.exe -E copy D:/vcpkg/buildtrees/tgui/x64-windows-dbg/gui-builder/gui-builder.exe D:/vcpkg/buildtrees/tgui/src/6c283daf87-fb8995dab3.clean/gui-builder/ && D:\vcpkg\downloads\tools\cmake-3.20.2-windows\cmake-3.20.2-windows-i386\bin\cmake.exe -E copy_directory D:/vcpkg/buildtrees/tgui/src/6c283daf87-fb8995dab3.clean/themes D:/vcpkg/buildtrees/tgui/src/6c283daf87-fb8995dab3.clean/gui-builder/themes""
LINK Pass 1: command "C:\PROGRA~2\MICROS~2\2019\COMMUN~1\VC\Tools\MSVC\1429~1.300\bin\Hostx64\x64\link.exe gui-builder\CMakeFiles\gui-builder.dir\src\main.cpp.obj gui-builder\CMakeFiles\gui-builder.dir\src\Form.cpp.obj gui-builder\CMakeFiles\gui-builder.dir\src\GuiBuilder.cpp.obj /out:gui-builder\gui-builder.exe /implib:gui-builder\gui-builder.lib /pdb:gui-builder\gui-builder.pdb /version:0.0 /machine:x64 /nologo /debug /INCREMENTAL /subsystem:windows lib\tgui-d.lib kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib /MANIFEST /MANIFESTFILE:gui-builder\CMakeFiles\gui-builder.dir/intermediate.manifest gui-builder\CMakeFiles\gui-builder.dir/manifest.res" failed (exit code 1120) with the following output:
MSVCRTD.lib(exe_winmain.obj) : error LNK2019: unresolved external symbol WinMain referenced in function "int __cdecl invoke_main(void)" (?invoke_main@@YAHXZ)
gui-builder\gui-builder.exe : fatal error LNK1120: 1 unresolved externals

That because here

TGUI/gui-builder/CMakeLists.txt

Lines 7 to 12 in dfcf16a

	# Make a GUI application on windows (without having the command line window)
	if(TGUI_OS_WINDOWS)
	set(GUI_TYPE WIN32)
	endif()
	add_executable(gui-builder ${GUI_TYPE} ${GUI_BUILDER_SOURCES})

set the entry point to WinMain, see cmake docs.
But in the source file

TGUI/gui-builder/src/main.cpp

Lines 38 to 42 in dfcf16a

	#ifdef TGUI_SYSTEM_WINDOWS
	int main(int, char**) // We don't use argv on Windows
	#else
	int main(int, char* argv[])
	#endif

All the entry points are main.

I can confirm that this issue still exist on the latest commit.

Can anyone help us?

Thanks.

[texus]

The gui-builder (which the "tool" option enables) can't be build without a rendering backend (i.e. with just the "core" configuration).
There used to be an error in this case, but it seems like it was accidentally removed. I'll add the error back soon.

The gui-builder links to either sfml-main or SDL2::SDL2main on Windows, which provide a WinMain function that calls the main function from the gui builder.

[texus]

An error message has been added again in 6e53b46.
The message might not be very clear to vcpkg users since it is meant for people who use cmake directly, but at least it will be more clear that some configuration is incorrect.