[src/trunk]: src/lib/libc/stdio When fflush fails, adjust pointers and the io...

[christos <christos%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/24c0a60f4691
branches:  trunk
changeset: 984683:24c0a60f4691
user:      christos <christos%NetBSD.org@localhost>
date:      Fri Jul 16 12:34:10 2021 +0000

description:
When fflush fails, adjust pointers and the io vectors. From RVP. Fixes
core-dump at cvs(1) exit(3).

diffstat:

 lib/libc/stdio/fvwrite.c |  44 ++++++++++++++++++++++++++++++++++++++------
 1 files changed, 38 insertions(+), 6 deletions(-)

diffs (72 lines):

diff -r f304d45867ee -r 24c0a60f4691 lib/libc/stdio/fvwrite.c
--- a/lib/libc/stdio/fvwrite.c  Fri Jul 16 12:20:01 2021 +0000
+++ b/lib/libc/stdio/fvwrite.c  Fri Jul 16 12:34:10 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: fvwrite.c,v 1.27 2021/07/08 09:06:51 christos Exp $    */
+/*     $NetBSD: fvwrite.c,v 1.28 2021/07/16 12:34:10 christos Exp $    */
 
 /*-
  * Copyright (c) 1990, 1993
@@ -37,7 +37,7 @@
 #if 0
 static char sccsid[] = "@(#)fvwrite.c  8.1 (Berkeley) 6/4/93";
 #else
-__RCSID("$NetBSD: fvwrite.c,v 1.27 2021/07/08 09:06:51 christos Exp $");
+__RCSID("$NetBSD: fvwrite.c,v 1.28 2021/07/16 12:34:10 christos Exp $");
 #endif
 #endif /* LIBC_SCCS and not lint */
 
@@ -51,6 +51,40 @@
 #include "local.h"
 #include "fvwrite.h"
 
+static int
+flush_adj(FILE *fp, struct __suio *uio, struct __siov *iov, ssize_t w)
+{
+       int rc;
+
+       _DIAGASSERT(w >= 0);
+       _DIAGASSERT(fp->_w >= 0);
+
+       if ((rc = fflush(fp)) == 0)
+               return 0;
+
+       /*
+        * If we have to return without writing the whole buffer,
+        * adjust for how much fflush() has written for us.
+        * `w' is the amt. of new user data just copied into our
+        * internal buffer in _this_ fwrite() call.
+         */
+       if (fp->_w < w) {
+               /* some new data was also written */
+               ssize_t i = w - fp->_w;
+
+               /* adjust amt. written */
+               uio->uio_resid -= i;
+               iov->iov_len -= i;
+       } else {
+               /* only old stuff was written */
+
+               /* adjust _p and _w so user can retry */
+               fp->_p -= w;
+               fp->_w += w;
+       }
+       return rc;
+}
+
 /*
  * Write some memory regions.  Return zero on success, EOF on error.
  *
@@ -102,10 +136,8 @@
        if (w <= 0) \
                goto err
 #define FLUSH(nw) \
-       if (fflush(fp)) { \
-               fp->_p -= nw;   /* rewind unwritten */ \
-               goto err; \
-       }
+       if (flush_adj(fp, uio, iov - 1, nw)) \
+               goto err
 
        if (fp->_flags & __SNBF) {
                /*