在 Windows 上使用 asprintf()

问题描述

我编写了一个在 linux 上完美运行的 C 程序，但是当我在 Windows 上编译它时，它给我一个错误，说 asprintf() 未定义.它应该是 stdio 库的一部分，但似乎许多编译器不包含它.我可以为 Windows 使用哪个编译器，它允许我使用 asprintf() 函数?我已经尝试了多个编译器，但到目前为止似乎没有一个定义它.

I have written a C program which works perfectly on linux, but when I compile it on windows, it gives me an error saying that asprintf() is undefined. It should be a part of the stdio library but it seems that many compilers do not include it. Which compiler can I use for windows which will allow me to use the asprintf() function? I have tried multiple compilers and none seem to define it so far.

推荐答案

asprintf() 函数不是 C 语言的一部分，并非在所有平台上都可用.Linux 拥有它的事实不寻常.

The asprintf() function is not part of the C language and it is not available on all platforms. The fact that Linux has it is unusual.

您可以使用 _vscprintf 和 _vsprintf_s 编写自己的代码.

You can write your own using _vscprintf and _vsprintf_s.

int vasprintf(char **strp, const char *fmt, va_list ap) {
    // _vscprintf tells you how big the buffer needs to be
    int len = _vscprintf(fmt, ap);
    if (len == -1) {
        return -1;
    }
    size_t size = (size_t)len + 1;
    char *str = malloc(size);
    if (!str) {
        return -1;
    }
    // _vsprintf_s is the "secure" version of vsprintf
    int r = _vsprintf_s(str, len + 1, fmt, ap);
    if (r == -1) {
        free(str);
        return -1;
    }
    *strp = str;
    return r;
}

这是从记忆中得出的，但它应该与您为 Visual Studio 运行时编写 vasprintf 的方式非常接近.

This is from memory but it should be very close to how you would write vasprintf for the Visual Studio runtime.

_vscprintf 和 _vsprintf_s 的使用是 Microsoft C 运行时独有的奇怪之处，您不会在 Linux 或 OS X 上以这种方式编写代码._s 版本，虽然标准化，但实际上在 Microsoft 生态系统之外并不经常遇到，而且 _vscprintf 甚至在其他地方都不存在.

The use of _vscprintf and _vsprintf_s are oddities unique to the Microsoft C runtime, you wouldn't write the code this way on Linux or OS X. The _s versions in particular, while standardized, in practice are not often encountered outside the Microsoft ecosystem, and _vscprintf doesn't even exist elsewhere.

当然，asprintf 只是对 vasprintf 的包装:

Of course, asprintf is just a wrapper around vasprintf:

int asprintf(char **strp, const char *fmt, ...) {
    va_list ap;
    va_start(ap, fmt);
    int r = vasprintf(strp, fmt, ap);
    va_end(ap);
    return r;
}

这不是编写 asprintf 的可移植"方式，但如果您的唯一目标是支持 Linux + Darwin + Windows，那么这是最好的方式.

This is not a "portable" way to write asprintf, but if your only goal is to support Linux + Darwin + Windows, then this is the best way to do that.

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