0006-Do-not-write-to-already-errored-stream.patch

From b5e22596184664f811e359700a8248d56220385c Mon Sep 17 00:00:00 2001
Message-Id: <f13ec12b59ba006ae177b0d9e041d908293792fa.1666072612.git.demi@invisiblethingslab.com>
In-Reply-To: <9d96ef018178fb73bc4a4aba121d49e453cc9796.1666072612.git.demi@invisiblethingslab.com>
References: <9d96ef018178fb73bc4a4aba121d49e453cc9796.1666072612.git.demi@invisiblethingslab.com>
From: Demi Marie Obenour <demi@invisiblethingslab.com>
Date: Tue, 18 Oct 2022 00:43:30 -0400
Subject: [PATCH 6/6] Do not write to already errored stream

If a stream has errored, writing further to it will just corrupt it.
This ensures that e.g. errors writing JSON output will cause invalid
JSON to be written.
---
 libdm/libdm-common.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/libdm/libdm-common.c b/libdm/libdm-common.c
index d75c7046c811e3b755a00a667c09c7758ef22b1e..d02b753129c883b701d34849012edfe8c321db0d 100644
--- a/libdm/libdm-common.c
+++ b/libdm/libdm-common.c
@@ -122,18 +122,24 @@ static void _default_log_line(int level, const char *file,
 		if (level < _LOG_WARN)
 			out = stderr;
 
+		if (ferror(out))
+			goto io_error;
+
 		if (_debug_with_line_numbers < 0)
 			/* Set when env DM_DEBUG_WITH_LINE_NUMBERS is not "0" */
 			_debug_with_line_numbers =
 				strcmp(getenv("DM_DEBUG_WITH_LINE_NUMBERS") ? : "0", "0");
 
 		if (_debug_with_line_numbers)
-			fprintf(out, "%s:%d     ", file, line);
+			if (fprintf(out, "%s:%d     ", file, line) < 0)
+				goto io_error;
 
-		vfprintf(out, f, ap);
+		if (vfprintf(out, f, ap) < 0)
+			goto io_error;
 		fputc('\n', out);
 	}
 
+io_error:
 	if (_abort_on_internal_errors < 0)
 		/* Set when env DM_ABORT_ON_INTERNAL_ERRORS is not "0" */
 		_abort_on_internal_errors =
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab