VSX-PCTS has found a SUS-conformance defect in our implementation of the
fwrite() interface.  According to the SUS:

======================================================================
RETURN VALUE

	The fwrite() function returns the number of members successfully
	written, which may be less than nitems if a write error is
	encountered. If size or nitems is 0, fwrite() returns 0 and the
	state of the stream remains unchanged. Otherwise, if a write
	error occurs, the error indicator for the stream is set and
	errno is set to indicate the error.
======================================================================

Yet when the following test program is run, the combination of:
	(a) element size of 0
	(b) element count of 1

yields fwrite() returning 1 -- SUS says above it should return 0 (when
*either* size or nitems is 0).

[snip]
#include <stdio.h>
#include <string.h>

#define FILENAME        "./testfile"
#define STRDATA         "This is a test\n"

main()
{
        FILE *fp;
        int val, len = strlen(STRDATA);

        if ((fp = fopen(FILENAME, "w")) == (FILE *) NULL) {
                perror(FILENAME);
                exit(1);
        }
        printf("fopen(\"%s\", \"w\") returns successfully\n", FILENAME);

        if ((val = fwrite(STRDATA, len, 1, fp)) != 1) {
                perror("fwrite(size != 0, count != 0)");
                fprintf(stderr, "fwrite() returned %d, expected 1\n", val);
                exit(1);
        }
        printf("fwrite(): [size != 0, count != 0] returns %d (success)\n",
		val);
        if ((val = fwrite(STRDATA, len, 0, fp)) != 0) {
                perror("fwrite(size != 0, count == 0)");
                fprintf(stderr, "fwrite() returned %d, expected 0\n", val);
                exit(1);
        }
        printf("fwrite(): [size != 0, count == 0] returns %d (success)\n",
		val);
        if ((val = fwrite(STRDATA, 0, 1, fp)) != 0) {
                perror("fwrite(size == 0, count != 0)");
                fprintf(stderr, "fwrite() returned %d, expected 0\n", val);
                exit(1);
        }
        printf("fwrite(): [size == 0, count != 0] returns %d (success)\n",
		val);
        (void) fclose(fp);
        exit(0);
}