Description of problem:

The man page for nice(2) states:

ERRORS
       EPERM  The  calling  process attempted to increase its priority by sup-
              plying a negative inc but has  insufficient  privileges.   Under
              Linux  the  CAP_SYS_NICE  capability  is required.  (But see the
              discussion of the RLIMIT_NICE resource limit in setrlimit(2).)

However, glibc() converts a call to nice(2) into a call to setpriority(2)
which WILL return with errno set to EACCES.

An strace of the program:

#include <errno.h>

main()
{
        if (nice(-19) < 0)
                printf("%d\n", errno);
}

shows it in reality calls:

setpriority(PRIO_PROCESS, 0, 4294967277) = -1 EACCES (Permission denied)

Version-Release number of selected component (if applicable):

glibc-2.4.8

How reproducible:

Run the test program above.

Steps to Reproduce:
1. Compile the code snippet above
2. Run
3. See incorrect errno set
  
Actual results:

failure with errno set to EACCES

Expected results:

failure with errno set to EPERM

Additional info:

This isn't just a man page error, as if the legacy nice syscall is invoked,
it reacts as documented.

For example, this program:

#include <sys/types.h>
#include <sys/syscall.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>

main()
{
        if (nice(-19) < 0)
                printf("%d\n", errno);

        if (syscall(__NR_nice, -19) < 0)
                printf("%d\n", errno);
}

will return:

$ ./a.out
13
1