xl: Break out flush_stream

We are going to want to reuse this.  Adjust the code slightly to
detect right away call sites that pass something other than stdout or
stderr.

No resulting functional change.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
---
v2: New patch in this version of the mini-series

diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
index c858068b397bd5ca964128fb620336058d2348f0..ee5578684c21dbf1bb66b8f32375f9762f0d3ffc 100644 (file)
--- a/tools/libxl/xl_cmdimpl.c
+++ b/tools/libxl/xl_cmdimpl.c
@@ -389,6 +389,20 @@ static yajl_gen_status printf_info_one_json(yajl_gen hand, int domid,
 out:
     return s;
 }
+
+static void flush_stream(FILE *fh)
+{
+    const char *fh_name =
+        fh == stdout ? "stdout" :
+        fh == stderr ? "stderr" :
+        (abort(), (const char*)0);
+
+    if (ferror(fh) || fflush(fh)) {
+        perror(fh_name);
+        exit(-1);
+    }
+}
+
 static void printf_info(enum output_format output_format,
                         int domid,
                         libxl_domain_config *d_config, FILE *fh)
@@ -424,13 +438,7 @@ out:
         fprintf(stderr,
                 "unable to format domain config as JSON (YAJL:%d)\n", s);
 
-    if (ferror(fh) || fflush(fh)) {
-        if (fh == stdout)
-            perror("stdout");
-        else
-            perror("stderr");
-        exit(-1);
-    }
+    flush_stream(fh);
 }
 
 static int do_daemonize(char *name)