bug#18621: [BUG] wc -c incorrectly counts bytes in /sys

[George Shuklin]

There is many sysfs (linux) attributes which reported as '4k files' but 
contains just a few bytes.

wc file and wc -c shows different sizes.
Example:

$cat /sys/kernel/vmcoreinfo
1b74c00 1024

$hexdump -Cv /sys/kernel/vmcoreinfo
00000000  31 62 37 34 63 30 30 20  31 30 32 34 0a           |1b74c00 1024.|
0000000d

$ls -la /sys/kernel/vmcoreinfo
-r--r--r-- 1 root root 4096 Oct  3 17:40 /sys/kernel/vmcoreinfo


Here wc output:

$ wc /sys/kernel/vmcoreinfo
   1    2   13 /sys/kernel/vmcoreinfo

and wc -c:

$ wc -c /sys/kernel/vmcoreinfo
4096 /sys/kernel/vmcoreinfo

4096 is not 13, and manual page for wc says that third number is byte count.

I think problem is in  cnt(const char *file)  function:

        if (dochar || domulti) {
                if (fstat(fd, &sb)) {
                        warn("%s: fstat", file);
                        (void)close(fd);
                        return (1);
                }
                if (S_ISREG(sb.st_mode)) {
                        (void)printf(" %7lld", (long long)sb.st_size);
                        tcharct += sb.st_size;
                        (void)close(fd);
                        return (0);
                }
        }