Fix mingw-w64 building

[apocelipes]

Since v0.23.1 cpp-httplib can not be complied with mingw-w64. The error message looks like this:

> D:\a\_temp\msys64\mingw64\bin\x86_64-w64-mingw32-g++ -c -m64 -std=c++11 -IC:\Users\runneradmin\AppData\Local\.xmake\packages\c\cpp-httplib\v0.25.0\cd2fddbf26ef4285ab9708e0209f52e0\include -o D:\a\_temp\msys64\tmp\.xmake\250808\_97BBC115DC5B437086AEA0BA215614B0.o D:\a\_temp\msys64\tmp\.xmake\250808\_7D0C25F8195246278D1C039D74425C23.cpp
> checking for c++ includes(httplib.h)
> checking for c++ snippet(test)
checkinfo: ...amdir\core\sandbox\modules\import\core\tool\compiler.lua:84: @programdir\modules\core\tools\gcc.lua:1035: In file included from D:\a\_temp\msys64\tmp\.xmake\250808\_7D0C25F8195246278D1C039D74425C23.cpp:2:
C:\Users\runneradmin\AppData\Local\.xmake\packages\c\cpp-httplib\v0.25.0\cd2fddbf26ef4285ab9708e0209f52e0\include/httplib.h: In member function 'bool httplib::detail::mmap::open(const char*)':
C:\Users\runneradmin\AppData\Local\.xmake\packages\c\cpp-httplib\v0.25.0\cd2fddbf26ef4285ab9708e0209f52e0\include/httplib.h:3081:14: error: '::CreateFile2' has not been declared; did you mean 'CreateFileW'?
 3081 |   hFile_ = ::CreateFile2(wpath.c_str(), GENERIC_READ, FILE_SHARE_READ,
      |              ^~~~~~~~~~~
      |              CreateFileW

You can find the whole CI log here: link

The function ::CreateFile2 needs _WIN32_WINNT >= 0x0602, however mingw-w64 in our CI cannot detect the correct value of it and set the value to 0x0600 and 0x0502, that makes the code cannot use CreateFile2.

Because cpp-httplib requires Windows 10 or newer, let's just set the _WIN32_WINNT to _WIN32_WINNT_WIN10 if we are using mingw-w64. Now mingw-w64 should compile the code.

[thbeu]

I consider this a kludge. Any chance to define/redefine _WIN32_WINNT to the appropriate value outside? Otherwise what about a macro HAVE_CREATEFILE2?

[apocelipes]

I consider this a kludge. Any chance to define/redefine _WIN32_WINNT to the appropriate value outside? Otherwise what about a macro HAVE_CREATEFILE2?

What can we do if HAVE_CREATEFILE2 was false? I think fall back to CreateFileW is acceptable.

Code could be like:

#if defined(HAVE_CREATEFILE2)
  hFile_ = ::CreateFile2(wpath.c_str(), GENERIC_READ, FILE_SHARE_READ,
                         OPEN_EXISTING, NULL);
#else
  hFile_ = ::CreateFileW(wpath.c_str(), GENERIC_READ, FILE_SHARE_READ, NULL,
                         OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
#endif

Edited: CreateFileW has different arguments, fixed.

[apocelipes]

The code has been updated. I add the macro HAVE_CREATEFILE2.

[yhirose]

@apocelipes thanks for the pull request. However, I don't prefer seeing __MINGW32__ and introducing another macro for this purpose. I made a different pull request to fix this issue at #2203. Could you please try it to see if it works on your machine, since I don't have the mingw-w64 environment? Thanks!

[yhirose]

Or, I am thinking to use only CreateFileW in httplib.h. :)

[apocelipes]

@yhirose Thanks for your review.

I think use CreateFile2 is fine because it is a modern and safer API.

The code can be simplified and no need to introduce a new macro. You could take a look at the new code:

#if _WIN32_WINNT >= _WIN32_WINNT_WIN8
  hFile_ = ::CreateFile2(wpath.c_str(), GENERIC_READ, FILE_SHARE_READ,
                         OPEN_EXISTING, NULL);
#else
  hFile_ = ::CreateFileW(wpath.c_str(), GENERIC_READ, FILE_SHARE_READ, NULL,
                         OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
#endif

This is more simple than use std::once_flag and no runtime performance cost.

[thbeu]

We already have the _WIN32_WINNT version check in

cpp-httplib/httplib.h

Lines 29 to 34 in 3f44c80

	#ifdef _WIN32
	#if defined(_WIN32_WINNT) && _WIN32_WINNT < 0x0A00
	#error \
	"cpp-httplib doesn't support Windows 8 or lower. Please use Windows 10 or later."
	#endif
	#endif

CreateFileW will not be used then.

[apocelipes]

So, the _WIN32_WINNT is greater than _WIN32_WINNT_WIN8 but CreateFile2 does not exist. It is toolchain's bug.

I can add a cmake check to set the macro HAVE_CREATEFILE2 but maybe it's not worth for it.

[apocelipes]

A cmake compile check has been added. PTAL.

[apocelipes]

I upgraded the toolchain and it fixed. I think this PR is no longer needed. Thank you for your advice.