Save errno before function call and restore it on success (because many

internal functions there may fail and set (i.e. overwrite) errno in normal
(not error) situation). In original variant errno testing after call
(as POSIX suggest) is wrong when errno overwrite happens.

2 files changed, 11 insertions, 2 deletions

diff --git a/lib/libc/stdio/fseek.c b/lib/libc/stdio/fseek.c
index e831347..38a8bf5 100644
--- a/lib/libc/stdio/fseek.c
+++ b/lib/libc/stdio/fseek.c
@@ -63,6 +63,7 @@ fseek(fp, offset, whence)
 	int whence;
 {
 	int ret;
+	int serrno = errno;
 
 	/* make sure stdio is set up */
 	if (!__sdidinit)
@@ -71,6 +72,8 @@ fseek(fp, offset, whence)
 	FLOCKFILE(fp);
 	ret = _fseeko(fp, (off_t)offset, whence, 1);
 	FUNLOCKFILE(fp);
+	if (ret == 0)
+		errno = serrno;
 	return (ret);
 }
 
@@ -81,6 +84,7 @@ fseeko(fp, offset, whence)
 	int whence;
 {
 	int ret;
+	int serrno = errno;
 
 	/* make sure stdio is set up */
 	if (!__sdidinit)
@@ -89,6 +93,8 @@ fseeko(fp, offset, whence)
 	FLOCKFILE(fp);
 	ret = _fseeko(fp, offset, whence, 0);
 	FUNLOCKFILE(fp);
+	if (ret == 0)
+		errno = serrno;
 	return (ret);
 }
 
diff --git a/lib/libc/stdio/rewind.c b/lib/libc/stdio/rewind.c
index af9232a..2db21c78 100644
--- a/lib/libc/stdio/rewind.c
+++ b/lib/libc/stdio/rewind.c
@@ -52,13 +52,16 @@ static const char rcsid[] =
 void
 rewind(FILE *fp)
 {
+	int serrno = errno;
+
 	/* make sure stdio is set up */
 	if (!__sdidinit)
 		__sinit();
 
 	FLOCKFILE(fp);
-	if (_fseeko(fp, (off_t)0, SEEK_SET, 1) == 0)
+	if (_fseeko(fp, (off_t)0, SEEK_SET, 1) == 0) {
 		clearerr_unlocked(fp);
+		errno = serrno;
+	}
 	FUNLOCKFILE(fp);
-	/* errno required by POSIX to sense error, don't zero it here */
 }