Fix fwrite() to return 0 when size or nmemb are zero.

Right now nmemb is returned when size is 0. In newer versions of the
standards, it is explicitly required that fwrite() should return 0.

Submitted by:	Christoph Mallon
Approved by:	re (kib)

1 files changed, 8 insertions, 1 deletions

diff --git a/lib/libc/stdio/fwrite.c b/lib/libc/stdio/fwrite.c
index 999d595..cf52e42 100644
--- a/lib/libc/stdio/fwrite.c
+++ b/lib/libc/stdio/fwrite.c
@@ -57,8 +57,15 @@ fwrite(buf, size, count, fp)
 	struct __suio uio;
 	struct __siov iov;
 
+	/*
+	 * ANSI and SUSv2 require a return value of 0 if size or count are 0.
+	 */
+	n = count * size;
+	if (n == 0)
+		return (0);
+
 	iov.iov_base = (void *)buf;
-	uio.uio_resid = iov.iov_len = n = count * size;
+	uio.uio_resid = iov.iov_len = n;
 	uio.uio_iov = &iov;
 	uio.uio_iovcnt = 1;