deque(size_t,const Allocator&) doesn't clear up constructed elements on exception

[achabense]

deque<T>(size_t,const Allocator&) lacks a tidy guard now. When the default constructor of a T throws, no destructor of constructed Ts will be called.

For example, in the code below, test([] {std::deque<resource>f(10); }); will print "created:5 destroyed:0". The expected behavior should be "created:5 destroyed:5" as the other code do.

#include<deque>
#include<iostream>

struct resource {
	inline static int created = 0, destroyed = 0;
	resource() {
		if (created == 5) { throw 0; }
		++created;
	}
	resource(const resource&) {
		if (created == 5) { throw 0; }
		++created;
	}
	~resource() { ++destroyed; }
};

void test(auto f) {
	resource::created = resource::destroyed = 0;
	try { f(); }
	catch (...) {}
	std::cout << "created:" << resource::created << " destroyed:" << resource::destroyed << std::endl;
}

int main() {
	//created:5 destroyed:0
	test([] {std::deque<resource>f(10); });
	//created:5 destroyed:5
	test([] {std::deque<resource>f; f.resize(10); });
	test([] {std::deque<resource>f; f.resize(10, resource{}); });
	test([] {std::deque<resource>f(10, resource{}); });
	test([] {std::deque<resource>f(10, resource{}, {}); });
}

Causes: In the implementation, the use of resize is wrong as it doesn't do cleanup on exception, and the construction is not completed so ~deque() won't be called either.

STL/stl/inc/deque

Lines 622 to 628 in a621095

	explicit deque(_CRT_GUARDOVERFLOW size_type _Count, const _Alloc& _Al = _Alloc())
	: _Mypair(_One_then_variadic_args_t{}, _Al) {
	_Alproxy_ty _Alproxy(_Getal());
	_Container_proxy_ptr12<_Alproxy_ty> _Proxy(_Alproxy, _Get_data());
	resize(_Count);
	_Proxy._Release();
	}

[CaseyCarter]

That's a nasty bug; thanks for the report.