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问题[x86-64](coding)

Martin Hope
khteh
Asked: 2025-02-07 21:34:01 +0800 CST
  • 6

我尝试使用以下代码片段在 64 位系统上计算阶乘：

long double FactorialLD(long n)
{
    long double result = 1;
    if (n <= 0)
        return 1;
    for (long i = 2; i <= n; i++)
        result *= i;
    return result;
}

30!返回265252859812191058647452510846976。但是，使用桌面计算器或https://www.calculatorsoup.com/calculators/discretemathematics/factorials.php返回265252859812191058636308480000000。为什么会有这么大的差异，是什么原因造成的？

CPU：英特尔x86_64

操作系统：Ubuntu 24.10

编译器：g++ 14.2.0

x86-64
Martin Hope
OrenIshShalom
Asked: 2024-10-26 13:58:25 +0800 CST
  • 7

我在我的树莓派上编译了一个 aarch64 elf 可执行文件：

$ file kbgen.elf.aarch64
kbgen.elf.aarch64: ELF 64-bit LSB executable, ARM aarch64, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-aarch64.so.1, for GNU/Linux 3.7.0, BuildID[sha1]=4cf36e84c30ea8e53073bb64cf99df1d82084702, with debug_info, not stripped

当我尝试在我的 x64 机器（wsl）上剥离它的符号时失败了：

$ strip kbgen.elf.aarch64
strip: Unable to recognise the format of the input file `kbgen.elf.aarch64'

这很奇怪，对吧？我的意思是精灵部分是“跨平台的”，不是吗？

# get inside raspberry pi to make sure stripping is ok there
$ ls -l kbgen.elf.aarch64
-rwxr-xr-x 1 oren oren 73257408 Oct 26 08:40 kbgen.elf.aarch64
$ sudo strip kbgen.elf.aarch64
$ ls -l kbgen.elf.aarch64 # <----- size reduced by a half, good !
-rwxr-xr-x 1 root root 36358680 Oct 26 08:42 kbgen.elf.aarch64

# make sure elf was stripped with file utility
$ file kbgen.elf.aarch64
kbgen.elf.aarch64: ELF 64-bit LSB executable, ARM aarch64, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-aarch64.so.1, for GNU/Linux 3.7.0, BuildID[sha1]=4cf36e84c30ea8e53073bb64cf99df1d82084702, stripped
x86-64