rand_s() issues

[bidnajunkeol]

I am trying to include rand_s() into my source code.

#define _CRT_RAND_S
#include <cstdlib>

I convinced this would work...

BUT IT DIDN'T!!! ARRGH!

1>.\main.cpp(23) : error C3861: 'rand_s': undeclared identifier

why doesn't this work?

anybody plz help me! OTL

[sohguanh]

Hmmm... is there rand_s() function ? From my Linux I only can see int rand(void) and void srand(unsigned int seed) available for use.

Above assume the default provided cstdlib.

[bidnajunkeol]

there IS a rand_s() in <stdlib.h>, although it is disabled when _CRT_RAND_S is not defined.

[sohguanh]

Can I know you are on which platform? Linux? Windows? etc etc.

[bidnajunkeol]

I am currently using Windows 7.

[sohguanh]

So most likely they do provide rand_s() function. I am referring to Linux cstdlib.h if you read my post correctly.

For your problem, maybe you need to link to some specific libraries (those that have rand_s() functions inside) on top of those default libraries provided in order to be able to access rand_s() function ?

[S6k9GNh0]

What compiler do you use?

http://cplusplus.com/forum/articles/31613/

[modoran]

This is an example from Visual Studio documentation. Does it wprk ?

// crt_rand_s.c
// This program illustrates how to generate random
// integer or floating point numbers in a specified range.

// Remembering to define _CRT_RAND_S prior
// to inclusion statement.
#define _CRT_RAND_S

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

int main( void )
{
    int             i;
    unsigned int    number;
    double          max = 100.0;
    errno_t         err;

    // Display 10 random integers in the range [ 1,10 ].
    for( i = 0; i < 10;i++ )
    {
        err = rand_s( &number );
        if (err != 0)
        {
            printf_s("The rand_s function failed!\n");
        }
        printf_s( "  %u\n", (unsigned int) ((double)number /
                       ((double) UINT_MAX + 1 ) * 10.0) + 1);
    }

    printf_s("\n");

    // Display 10 random doubles in [0, max).
    for (i = 0; i < 10;i++ )
    {
        err = rand_s( &number );
        if (err != 0)
        {
            printf_s("The rand_s function failed!\n");
        }
        printf_s( "  %g\n", (double) number / 
                          ((double) UINT_MAX + 1) * max );
    }
}

Of course rand_s does not work in Linux as it uses internally RtlGenRandom API, which is only available in Windows XP and later.

[kbw]

The _s functions in Visual Studio 2005 and beyond are "safe" versions. They are not portable and will only work with Microsoft compilers.

BTW, Microsoft aren't the only ones (or first ones) to provide "safe" versions of standard C library functions. For example, OpenBSD provides "safe" versions of string functions.

[Disch]

how is rand() "unsafe"? what's the point of rand_s()?

[kbw]

I didn't quite see the point either. I never use the "safe" versions of the Microsoft Functions.

I'm generally unsupportive of divergent standards, especially the pointless ones.

[S6k9GNh0]

See the post here: http://www.devmaster.net/forums/showthread.php?t=12246