对std :: regex_match（和std :: regex_search）的参数的生命周期的约束 [英] Constraints on the lifetime of the argument to std::regex_match (and std::regex_search)

问题描述

考虑C ++ 11函数的signaturer std :: regex_match（
std :: string const& std :: smatch& match，std :: regex const& re） ，什么
是第一个参数的生命周期的约束？我没有找到
任何，但是当我执行以下程序（使用VC ++ 2010编译，
迭代器调试活动）：

Considering the C++11 function with the signaturer std::regex_match( std::string const&, std::smatch& match, std::regex const& re ), what are the constraints on the lifetime of the first argument? I don't find any, but when I execute the following program (compiled with VC++ 2010, iterator debugging active):

int
main()
{
    std::string a("aaa");
    std::string c("ccc");
    std::regex re("aaa(.*)ccc");
    std::smatch m;
    if (std::regex_match(a + "xyz" + c, m, re)) {
        std::cout << m[0] << std::endl;
        std::cout << m[1] << std::endl;
    }
    return 0;
}

它崩溃，无疑是因为 sub_match 在 m 只保留
迭代器到字符串，而不是副本。我不能在禁止我的代码
标准中找到任何东西。

it crashes, doubtlessly because the sub_match in m only keep iterators into the string, and not copies. I can't find anything in the standard which forbids my code.

FWIW：它不能在 boost :: regex ，这也是基于
std :: regex 的原因。 （当然，Boost没有记录关于生命周期的任何
约束。）

FWIW: it didn't work in boost::regex, either, and that's what the std::regex is based on. (Of course, Boost didn't document any constraints with regards to the lifetime either.)

最后，我想我的问题是：发送一个DR到
标准组织，或者向Microsoft提交错误报告？

In the end, I guess my question is: should I send in a DR to the standards organization, or a bug report to Microsoft?

推荐答案

在采用 tr1 :: regex 或 std :: regex 期间对此可能性的任何讨论，所以我认为没有考虑。事后看来，这当然是我们应该预见的一个陷阱。在我的头顶部，一个重载，需要一个 std :: string&&& 会指示涉及一个临时，需要一个副本。所以我要向标准委员会报告。 （完全公开：我写了Dinkumware实现，这是微软的船）

I don't recall any discussion of this possibility during the adoption of tr1::regex or std::regex, so I think it simply was not considered. In hindsight, it's certainly a trap that we should have foreseen. Off the top of my head, an overload that takes a std::string&& would signal that a temporary is involved, and a copy is needed. So I'd report it to the Standards Committee. (full disclosure: I wrote the Dinkumware implementation, which is what Microsoft ships)

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