include: add stream error checking facility

The close_stream() is copied from GNU lib.  Inspiration to do this is
talk by Jim Meyering - Goodbye World! The perils of relying on output
streams in C.

Reference: http://www.irill.org/events/ghm-gnu-hackers-meeting/videos/jim-meyering-goodbye-world-the-perils-of-relying-on-output-streams-in-c
Signed-off-by: Sami Kerola <kerolasa@iki.fi>

1 files changed, 41 insertions, 0 deletions

diff --git a/include/closestream.h b/include/closestream.h
new file mode 100644
index 000000000..fb507eab8
--- /dev/null
+++ b/include/closestream.h
@@ -0,0 +1,41 @@
+#ifndef UTIL_LINUX_CLOSESTREAM_H
+#define UTIL_LINUX_CLOSESTREAM_H
+
+#include <stdio.h>
+#include <stdio_ext.h>
+#include <unistd.h>
+
+#include "c.h"
+#include "nls.h"
+
+static inline int
+close_stream(FILE * stream)
+{
+	const int some_pending = (__fpending(stream) != 0);
+	const int prev_fail = (ferror(stream) != 0);
+	const int fclose_fail = (fclose(stream) != 0);
+	if (prev_fail || (fclose_fail && (some_pending || errno != EBADF))) {
+		if (!fclose_fail)
+			errno = 0;
+		return EOF;
+	}
+	return 0;
+}
+
+/* Meant to be used atexit(close_stdout); */
+static inline void
+close_stdout(void)
+{
+	if (close_stream(stdout) != 0 && !(errno == EPIPE)) {
+		if (errno)
+			warn(_("write error"));
+		else
+			warnx(_("write error"));
+		_exit(EXIT_FAILURE);
+	}
+
+	if (close_stream(stderr) != 0)
+		_exit(EXIT_FAILURE);
+}
+
+#endif /* UTIL_LINUX_CLOSESTREAM_H */