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)

2 files changed, 9 insertions, 4 deletions

diff --git a/lib/libc/stdio/fread.c b/lib/libc/stdio/fread.c
index 851713b..6253856 100644
--- a/lib/libc/stdio/fread.c
+++ b/lib/libc/stdio/fread.c
@@ -67,9 +67,7 @@ __fread(void * __restrict buf, size_t size, size_t count, FILE * __restrict fp)
 	size_t total;
 
 	/*
-	 * The ANSI standard requires a return value of 0 for a count
-	 * or a size of 0.  Peculiarily, it imposes no such requirements
-	 * on fwrite; it only requires fread to be broken.
+	 * ANSI and SUSv2 require a return value of 0 if size or count are 0.
 	 */
 	if ((resid = count * size) == 0)
 		return (0);
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;