G＆＃x2b;＆＃x2B;以及clang的处理VLAS定义和初始化的C＆＃x2b;＆＃x2b;＆＃x24

发布于 2025-02-07 21:18:06 字数 508 浏览 0 评论 0原文

源代码如下：

using namespace std;

int main()
{
        int m = 4;
        int arr[m] = {1, 2, 3, 4};
        printf("%d\n", arr[2]);
        return 0;
}

当我使用 g ++ 编译时，它将成功编译为可执行文件。但是，当我用 clang ++ 编译时，我会收到以下错误：

VLAs.cpp:8:10: error: variable-sized object may not be initialized
        int arr[m] = {1, 2, 3, 4};
                ^
1 error generated.

测试后，我发现clang ++可以支持VLBS的定义。，但在初始化它们时不支持定义VLB。我想知道这种差异的根本原因

原文

The source code as follows：

using namespace std;

int main()
{
        int m = 4;
        int arr[m] = {1, 2, 3, 4};
        printf("%d\n", arr[2]);
        return 0;
}

When I compile with g++, it compiles successfully as an executable. But when I compile with clang++, I get the following error：

VLAs.cpp:8:10: error: variable-sized object may not be initialized
        int arr[m] = {1, 2, 3, 4};
                ^
1 error generated.

After testing, I found that clang ++ can support the definition of VLBs（int arr[m]；）, but does not support defining VLBs while initializing them. I would like to know the root cause of this difference

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轻许诺言 2025-02-14 21:18:06

VLA不是C ++，编译器以不同的方式支持它们。在C初始化VLA中，不支持VLA，这似乎也是Clang在C ++中所做的。另一方面，海湾合作委员会稍微扩大了对VLA的支持。您的下一个编译器可能根本没有VLA。

那么，如果C ++对此具有较高的机制，为什么要打扰：

#include <vector>
#include <array>

constexpr int n = 4;
std::array arr{1, 2, 3, 4};
std::array<int, n> arr2 = {1, 2, 3, 4};
std::vector<int> arr3 = {1, 2, 3, 4};

VLAs are not C++ and compiler support them differently. In C initializing VLAs is not supported and that seems to be what clang does in c++ as well. gcc on the other hand has extended the support for VLAs a bit. Your next compiler might not have VLAs at all.

So why bother if C++ has far superior mechanisms for this:

#include <vector>
#include <array>

constexpr int n = 4;
std::array arr{1, 2, 3, 4};
std::array<int, n> arr2 = {1, 2, 3, 4};
std::vector<int> arr3 = {1, 2, 3, 4};

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