c++ - Visual Studio 和 Clang 不会抛出 std::bad_array_new_length

Question

这是对 prior question 的跟进.

在以下程序中 Visual Studio 2015 and Clang两者都不会抛出 std::bad_array_new_length。 gcc does .

#include <iostream>
#include <random>
#include <exception>
#include <new>

int main()
{
    std::random_device rd;
    std::uniform_int_distribution<int> dist(2,2);
    try {

        auto arr = new int[dist(rd)][4][2]{{{1}},{{2}},{{3}}}; // may write to unallocated memory

        auto val1 = arr[0][0][0];
        auto val2 = arr[1][0][0];
        auto val3 = arr[2][0][0];
        auto result = val1 + val2 + val3;
        std::cout << result;
    }
    catch (std::exception const& e) {
        std::cerr << e.what() << '\n';
    }
    return 0;
}

在 Visual Studio 中，程序崩溃时没有任何消息。在 Clang 中没有错误(可能是因为它是 avoided the allocation 中提到的 this answer )。

三个编译器，三个结果。这是未定义的行为还是 Visual Studio 中的错误？

Answer 1

GCC 是正确的，行为由标准定义。

$5.3.4/7 新 [expr.new]

The expression in a noptr-new-declarator is erroneous if:

...

(7.4) — the new-initializer is a braced-init-list and the number of array elements for which initializers are provided (including the terminating ’\0’ in a string literal (2.13.5)) exceeds the number of elements to initialize.

...

a new-expression with an erroneous expression does not call an allocation function and terminates by throwing an exception of a type that would match a handler (15.3) of type std::bad_array_new_length (18.6.2.2).