[boost] boost.context cause strange crash on certan WIN32 API

28 Nov 2014

      Hi, I was using Boost.Asio.Spawn happliy until I ported my project to windows.

I got stange openssl crash. many debug days speeded and there was nothing 
wrong with openssl.

Strange thing is, openssl didn't crash when used in normal code, unless I used 
them in asio stackful coroutine.

Now I finnally find the root cause and make it 100% reproducible.

here is the code that demostrade the crash:

<code>

boost::context::fcontext_t fcm,fc1;

void f1(intptr_t)
{
	HMODULE advapi = LoadLibrary(TEXT("advapi32")); // crash there
	FreeLibrary(advapi);
	boost::context::jump_fcontext(fc1, &fcm, 0);
}

std::thread([](){
	boost::context::guarded_stack_allocator alloc;
	std::size_t size(8192);
	void* sp1(std::malloc(size));

	fc1=boost::context::make_fcontext(sp1, size, f1);
	boost::context::jump_fcontext(&fcm, fc1, 0);
});

</code>

the context created in threads other that main thread, can't call certain 
APIs. If LoadLibrary get called by an context that created in thread, it will 
crash.

100% reproducible on WIN64 platform with MSVC2013.
And nothing wrong on WIN32 !

[boost] boost.context cause strange crash on certan WIN32 API

microcai