From 8bedfb6eb45f75f22c0887adaa3d2e648247bff7 Mon Sep 17 00:00:00 2001
From: Ian Rees <ian.rees@gmail.com>
Date: Mon, 5 Oct 2020 16:37:04 +1300
Subject: [PATCH] Don't close output file after writing first graph

Fixes #1845, essentially by reverting 806b8a2f
---
 cmd/dot/dot.c      | 2 +-
 lib/gvc/gvdevice.c | 7 +++++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/cmd/dot/dot.c b/cmd/dot/dot.c
index 631448663..445fefb6b 100644
--- a/cmd/dot/dot.c
+++ b/cmd/dot/dot.c
@@ -131,12 +131,12 @@ int main(int argc, char **argv)
 	    }
 	    gvLayoutJobs(Gvc, G);  /* take layout engine from command line */
 	    gvRenderJobs(Gvc, G);
-            gvFinalize(Gvc);
 	    r = agreseterrors();
 	    rc = MAX(rc,r);
 	    prev = G;
 	}
     }
+    gvFinalize(Gvc);
     r = gvFreeContext(Gvc);
     return (MAX(rc,r));
 }
diff --git a/lib/gvc/gvdevice.c b/lib/gvc/gvdevice.c
index 0a9951186..03a348d02 100644
--- a/lib/gvc/gvdevice.c
+++ b/lib/gvc/gvdevice.c
@@ -46,6 +46,7 @@ static unsigned int dfallocated;
 static uint64_t crc;
 #endif /* HAVE_LIBZ */
 
+#include <assert.h>
 #include <common/const.h>
 #include <common/memory.h>
 #include <gvc/gvplugin_device.h>
@@ -76,8 +77,10 @@ static size_t gvwrite_no_z (GVJ_t * job, const char *s, size_t len)
 	job->output_data[job->output_data_position] = '\0'; /* keep null termnated */
 	return len;
     }
-    else
-	return fwrite(s, sizeof(char), len, job->output_file);
+    else {
+        assert(job->output_file != NULL);
+        return fwrite(s, sizeof(char), len, job->output_file);
+    }
     return 0;
 }
 
-- 
2.40.0