test/libcjson: add diag output on open failure

src/common/libcjson/test.c

@@ -23,11 +23,14 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <limits.h>
-#include "cJSON.h"
+#include <errno.h>
+#include <string.h>
 
 #include "src/common/libutil/xzmalloc.h"
 #include "src/common/libtap/tap.h"
 
+#include "cJSON.h"
+
 /* Parse text to JSON, then render back to text, and print! */
 int doit(char *text)
 {
@@ -56,11 +59,14 @@ int dofile(char *filename)
 	char path[PATH_MAX+1];
 	snprintf (path, sizeof (path), "%s/%s", SRCDIR, filename);
 	f=fopen(path,"rb");
-	if (f == NULL)
+	if (f == NULL) {
+		diag ("%s: %s", path, strerror (errno));
 		return 0;
+	}
 	fseek(f,0,SEEK_END);len=ftell(f);fseek(f,0,SEEK_SET);
 	data=(char*)xzmalloc(len+1);
 	if (fread(data,1,len,f) != len) {
+		diag ("%s: fread %d failed", path, len);
 		fclose (f);
 		return 0;
 	}