问题标签 [int64]

我正在尝试用 C++ 为 Windows（MinGW）和 Linux（g++）编写跨平台代码。我习惯在 Linux 中将 64 位整数定义为“long”，但是当我转到 MinGW 时，sizeof(long) 返回 4 个字节。然后我发现我可以在 MinGW 中使用“long long”或“__INT64”来定义 64 位整数。我有两个问题：

1.-为 Windows 和 Linux 定义 64 位整数的最便携方式是什么？我目前正在使用#ifdef，但我不知道这是否是最好的方法：

2.-我应该在 MinGW 中使用“long long”还是“__INT64”？为什么？

我从带有长类型限定符的第 3 方软件中得到一个字符串，例如“1L”。我想将其解析为 Int64，但 Int64.TryParse 无法将其识别为 Int64。有没有一种 .NET 方法可以安全地做到这一点？我想避免解析自己...

谢谢你的帮助！

From following code I expect to set all bits in x to 1, but somehow only first 32 bits are set:

Note: printing x after each line results in 4294967295 (32 lower bits set to 1). Also, tried using numeric_limits<int64_t>::min() with no success. My question is how to set all bits in x? Using RHEL5.5.

Thx

设a、b、c为long long (int64)数，如何计算(a*b)%c？这里的问题是你不能乘以 (a%c)*(b%c) 因为它不适合 int64 变量。那么，它可以做什么呢？

以防万一它有帮助，我正在使用 C++。

我试过：

fmt.Printf("%d", math.MaxUint64)

但我收到以下错误消息：

常量 18446744073709551615 溢出 int

我怎样才能解决这个问题？谢谢！

__int64我对和有问题%I64u。或者我的公式可能有问题。我试图模仿下面的输出。但是在某些订单项中发生了一件奇怪的事情。我不明白发生了什么，因为其他人打印得很好。

注意：这些列表的主要来源来自二进制原始数据。所以我从十六进制中获取它并尝试将其转换为__int64. 我的列表由120行项目组成，这些行项目输出良好，73并且从行中失败74，预期值为2276812558并显示18446744071691396878。从排队74到排队120的结果是intermittent。其他没问题，其他线路失败。

有人帮忙吗？？

资源：

这是我的代码：

.输出产生

Our C++ library currently uses time_t for storing time values. I'm beginning to need sub-second precision in some places, so a larger data type will be necessary there anyway. Also, it might be useful to get around the Year-2038 problem in some places. So I'm thinking about completely switching to a single Time class with an underlying int64_t value, to replace the time_t value in all places.

Now I'm wondering about the performance impact of such a change when running this code on a 32-bit operating system or 32-bit CPU. IIUC the compiler will generate code to perform 64-bit arithmetic using 32-bit registers. But if this is too slow, I might have to use a more differentiated way for dealing with time values, which might make the software more difficult to maintain.

What I'm interested in:

• which factors influence performance of these operations? Probably the compiler and compiler version; but does the operating system or the CPU make/model influence this as well? Will a normal 32-bit system use the 64-bit registers of modern CPUs?
• which operations will be especially slow when emulated on 32-bit? Or which will have nearly no slowdown?
• are there any existing benchmark results for using int64_t/uint64_t on 32-bit systems?
• does anyone have own experience about this performance impact?

I'm mostly interested in g++ 4.1 and 4.4 on Linux 2.6 (RHEL5, RHEL6) on Intel Core 2 systems; but it would also be nice to know about the situation for other systems (like Sparc Solaris + Solaris CC, Windows + MSVC).

如何将程序参数从 转换argv为int64_t？atoi()仅适用于 32 位整数。

I want to send two int64_t over UDP. To do this I store them in a four-element array, where:

• [0] - lower 32 its of the first int64_t
• [1] - higher 32 bits of the first int64_t
• [2] - lower 32 bits of the second int64_t
• [3] - higher 32 bits if the second int64_t

My code for sending:

My code for combining int32_t back to int64_t after receiving data via UDP:

The first number (from) is always correct. However, what I get from the second printf is incorrect. What's more, it seems to be dependent on the first number. Example:

Sending:

• from = 125,
• to = 20.

Received:

• from = 125,
• to = 125.

Sending:

• from = 1252,
• to = 20.

Received:

• from = 1252,
• to = 1268.

What am I doing wrong? Is it the problem of conversion or sending over the network?

我不是 C 或 C++ 方面的老手。我不知道如何time_t定义和设计。几个帖子，如：

• time_t typedef 最终是什么？
• C中的size_t是什么？
• size_t 和 std::size_t 之间的区别

但这些帖子只说明什么是time_t或size_t。它没有明确说明 time_t 或 size_t 是如何以及在何处定义和声明的。

我正在使用WIN8 VS2012 Express C++。我搜索了库，发现它size_t是在crtdefs.h而不是cstddef.

• 为什么需要像size_t,之类的类型time_t？我们可以让sizeof只是返回unsigned int。
• 为什么 C++ 库没有定义size_t？
• 我可以说 size_t不是C/C++ 内置类型吗？
• 我永远不需要在我的程序中包含相应的头文件来使用size_t或time_t（也许它们是在std命名空间中定义的）。

我在库中再次搜索，发现size_t定义为typedef _W64 unsigned int size_t，_W64定义为__w64。在这里，我无法更多地搜索__w64定义或声明的位置。

• 什么是__w64类型？C++11/C99 标准中没有说明。

同样，当我搜索 时time_t，我发现__int6. 却不知从何__int64而来。