Visual Studio 2015中的安全功能

Question

While coding C under windows,visual studio 2015,I found my self forced to amend my code due to the deprecated functions,by adding a second parameter,and of course using a safe function(eg ending with _s).

I was wondering,do these functions exist in the C standard library,and will i be able to compile them with a C compiler if I transfer them to my linux partition?

My concern arose when i was writing a string flip about an offset function:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char *flipstr(char *str, size_t size, size_t offset);

int main(int , char **)
{
    char str[] = "JonSon";
    char *p = flipstr(str, sizeof(str), 3);
    if (p) {
        printf("%s\n", p);
    }
    return 0;
}

char *flipstr(char *str, size_t size, size_t offset)
{
    if (offset > strlen(str)) {
        return NULL;
    }

    char *tmp = (char *)calloc(size, sizeof(char));

    strncpy_s(tmp, size, str, offset);

    memmove(str, str + offset, strlen(str + offset));

    memcpy(str + strlen(str + offset), tmp, strlen(tmp));

    free(tmp);

    return str;
}

Answer 1

No, most of them aren't standard and you shouldn't use them just because somebody in Microsoft decided to "deprecate" half the standard library in favor of their non-standard extensions. Sure, there is some justification of what they did, but in the end it's simply ridiculous. You are better to disable the warnings and write a portable C/C++.

Answer 2

There are several issues here...

First of all, there is nothing wrong with using strcpy , that's a myth. And it is not deprecated, that's just Microsoft gaga.

Second, strncpy was never intended to be a safe version of strcpy . It was never intended to be used for anything but an old, non-standard string format in ancient Unix.

Third, strncpy is unsafe and dangerous. See this and this . Plenty of blogs about this to be found.

So forget about strncpy , and consequently, also forget about strncpy_s . There is actually a function called strncpy_s in the C11 bounds-checking interface (which isn't mandatory for compilers to implement).

If this C11 standard function is fully compatible with non-standard Microsoft junk functions with the same name, I have no idea. I wouldn't count on it. But since Visual Studio 2015 is an ancient compiler from the early 90s, C11 is not something you can use anyhow.