嵌套的lambdas導致編譯器用完堆

我正在撰寫一些將 lambda 函式傳遞給一組遞回函式的代碼。其中一些 lambda 函式嵌套在其他 lambda 函式中。我想我正在撰寫有效的代碼，但我遇到了fatal error C1060: compiler is out of heap space錯誤。

這是代碼的精簡版本

struct Null
{
    template <typename SK>
    static void match(SK sk)
    {
    }
};

template <typename T>
struct Repetition
{
    template <typename SK>
    static void match(SK sk)
    {  // <--------------------------------- error message points to this line
        T::match([]() { match([]() {}); });
    }
};

int main()
{
    using Test = Repetition<Null>;
    Test::match([](){});
}

現在這個最小版本沒有多大意義，但它有相同的編譯器錯誤。我已經指出了上面錯誤的行。

我的問題是，這是編譯器錯誤/限制還是我的代碼在某種程度上無效？

編譯器是編譯 C 20 的 Visual Studio 2022。

謝謝

uj5u.com熱心網友回復：

每[expr.prim.lambda.closure]

lambda 運算式的型別（也是閉包物件的型別）是唯一的、未命名的非聯合型別別

要實體化Repetition::match，編譯器必須實體化Null::match，這需要Repetition::match...的實體化，依此類推。每次編譯器遞回時，[]() {}都被視為一種全新的型別，無限回圈。

要讓它停止遞回，請將您的呼叫替換為：

T::match(sk);

uj5u.com熱心網友回復：

雖然 VS2022 和 gcc 11 和 12 都崩潰了，但 clang 確實設法給出了一條錯誤訊息：

<source>:15:25: fatal error: recursive template instantiation exceeded maximum depth of 1024
        T::match([]() { match([]() {}); });
                        ^
<source>:15:25: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:15:31)>' requested here
<source>:15:25: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:15:31)>' requested here
<source>:15:25: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:15:31)>' requested here
<source>:15:25: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:15:31)>' requested here
<source>:15:25: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:15:31)>' requested here
<source>:15:25: note: (skipping 1015 contexts in backtrace; use -ftemplate-backtrace-limit=0 to see all)
<source>:15:25: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:15:31)>' requested here
<source>:15:25: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:15:31)>' requested here
<source>:15:25: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:15:31)>' requested here
<source>:15:25: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:15:31)>' requested here
<source>:22:11: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:22:17)>' requested here
    Test::match([](){});
          ^
1 error generated.
ASM generation compiler returned: 1
<source>:15:25: fatal error: recursive template instantiation exceeded maximum depth of 1024
        T::match([]() { match([]() {}); });
                        ^
<source>:15:25: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:15:31)>' requested here
<source>:15:25: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:15:31)>' requested here
<source>:15:25: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:15:31)>' requested here
<source>:15:25: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:15:31)>' requested here
<source>:15:25: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:15:31)>' requested here
<source>:15:25: note: (skipping 1015 contexts in backtrace; use -ftemplate-backtrace-limit=0 to see all)
<source>:15:25: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:15:31)>' requested here
<source>:15:25: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:15:31)>' requested here
<source>:15:25: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:15:31)>' requested here
<source>:15:25: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:15:31)>' requested here
<source>:22:11: note: in instantiation of function template specialization 'Repetition<Null>::match<(lambda at <source>:22:17)>' requested here
    Test::match([](){});
          ^
1 error generated.
Execution build compiler returned: 1

標籤：C c 11

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