fixed 'localtime_*' compilation error MinGW

[Schebb]

I got the following compilation error when compiling a project including websocketpp with MinGW:

[ 95%] Building CXX object CMakeFiles/Sources/MyProject/CMakeFiles/MyProject.dir/TestClient.cpp.obj
In file included from F:/Project/MyProject/build/cmake/../../extlibs/include/websocketpp/logger/basic.hpp:49:0,
from F:/Project/MyProject/build/cmake/../../extlibs/include/websocketpp/config/core.hpp:51,
from F:/Project/MyProject/build/cmake/../../extlibs/include/websocketpp/config/asio_no_tls.hpp:31,
from F:\Project\MyProject\Sources\MyProject\WebSocketClient.hpp:8,
from F:\Project\MyProject\Sources\MyProject\TestClient.hpp:34,
from F:\Project\MyProject\Sources\MyProject\TestClient.cpp:2:
F:/Project/MyProject/build/cmake/../../extlibs/include/websocketpp/common/time.hpp: In function 'tm websocketpp::lib::localtime(const time_t&)':
F:/Project/MyProject/build/cmake/../../extlibs/include/websocketpp/common/time.hpp:44:36: error: 'localtime_s' was not declared in this scope
localtime_s(&tm_snapshot, &time);
^
compilation terminated due to -Wfatal-errors.
CMakeFiles\Sources\MyProject\CMakeFiles\MyProject.dir\build.make:57: recipe for target 'CMakeFiles/Sources/MyProject/CMakeFiles/MyProject.dir/TestClient.cpp.obj' failed
make[3]: *** [CMakeFiles/Sources/MyProject/CMakeFiles/MyProject.dir/TestClient.cpp.obj] Error 1
CMakeFiles\Makefile2:1063: recipe for target 'CMakeFiles/Sources/MyProject/CMakeFiles/MyProject.dir/all' failed
make[2]: *** [CMakeFiles/Sources/MyProject/CMakeFiles/MyProject.dir/all] Error 2
CMakeFiles\Makefile2:1075: recipe for target 'CMakeFiles/Sources/MyProject/CMakeFiles/MyProject.dir/rule' failed
make[1]: *** [CMakeFiles/Sources/MyProject/CMakeFiles/MyProject.dir/rule] Error 2

Makefile:329: recipe for target 'MyProject' failed
make: *** [MyProject] Error 2

Note

MinGW does not define neither localtime_s nor locatime_r.

Discussion here: http://stackoverflow.com/questions/18551409/localtime-r-support-on-mingw
MinGW Note here: http://sourceforge.net/p/mingw-w64/mailman/message/21523522/

[Schebb]

I naively took my change from #392
but It appears my project cannot compile with this branch (develop) of websocketpp. I got an error about the header of std::mutex that is missing. (I will check this after lunching)

[Schebb]

concerning my previous comment: my error about std::mutex is due to MinGW (again :s) that still haven't a standard threads implementation.

Users of MinGW can either:

• use this implementation https://github.com/meganz/mingw-std-threads
• or simply add -D_WEBSOCKETPP_NO_CPP11_THREAD_ to the compilation line for switching to boost's threads (I did that: no other error, it works perfectly).

(we could detect MinGW and automatically add this macro in the code or just wait the MinGW's team)

Anyway, I don't know why travis failed here.

[zaphoyd]

travis failed due to a finicky timer test that I should probably remove since it gets a lot of false positives.

Falling back to boost thread would be a good default here. I'll look into autodetecting that. A few things you could help me with in that regard:

• Does MinGW have a "C++11 mode/switch" in the way that g++ does with -std=c++11? If so are you using it?
• When used in C++11 mode, either via the switch or because its always on, what is the value of the __cplusplus define?

[Schebb]

I am not an expert in MinGW, so I compiled this code for answering your question:

#include <iostream>

int main( void ) {
    auto func = [] { std::cout << "__cplusplus : " << __cplusplus << std::endl; };
    func();
    return 0;
}

and I got the following input:

C:\Users\Scheb\Desktop\testmingw>mingw32-g++ --version
mingw32-g++ (GCC) 4.8.1
Copyright (C) 2013 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.


C:\Users\Scheb\Desktop\testmingw>mingw32-g++ -o test main.cpp
main.cpp: In function 'int main()':
main.cpp:5:7: error: 'func' does not name a type
  auto func = [] { std::cout << "__cplusplus : " << __cplusplus << std::endl; };

       ^
main.cpp:6:7: error: 'func' was not declared in this scope
  func();
       ^

C:\Users\Scheb\Desktop\testmingw>mingw32-g++ -o test main.cpp -std=c++11

C:\Users\Scheb\Desktop\testmingw>test.exe
__cplusplus : 201103

Consequently, I would answer

1. Yes, same as g++ (as often); it is "-std=c++11"
2. oh, I didn't know the value of __cplusplus could be useful.. Here, in C++11 mode it is '201103' (and without c++11 mode activated, it is 199711).

[zaphoyd]

I've pushed an update to the C++11 thread support detection code that should force the use of boost thread by default for MinGW even when it is building in C++11 mode. Can you confirm that this fixes the issue you were seeing without requiring you to include any special preprocessor defines?

[Schebb]

Confirmed; I checkout from 'develop' branch (replaced websocketpp\common\time.hpp with the changes on this pull request) and no error.

Note that in "if (defined(MINGW32) || defined(MINGW64))", checking MINGW64 is not really necessary because I think mingw64 defines also MINGW32. Thus, checking MINGW32 alone could be enough. But for me, it's more clear for an external readers that might think MINGW64 is missing.