[GitHub] [qpid-dispatch] kgiusti commented on a change in pull request #599: DISPATCH-1461: correct the logging of long addresses on attach

[GitBox <gi...@apache.org>]

kgiusti commented on a change in pull request #599: DISPATCH-1461: correct the logging of long addresses on attach
URL: https://github.com/apache/qpid-dispatch/pull/599#discussion_r339190898
 
 

 ##########
 File path: src/router_core/terminus.c
 ##########
 @@ -76,30 +76,49 @@ void qdr_terminus_free(qdr_terminus_t *term)
 }
 
 
+// DISPATCH-1461: snprintf() is evil - it returns >= size on overflow.  This
+// wrapper will never return >= size, even if truncated.  This makes it safe to
+// do pointer & length arithmetic without overflowing the destination buffer in
+// qdr_terminus_format()
+//
+static inline int safe_snprintf(char *str, size_t size, const char *format, ...)
+{
+    va_list ap;
+    va_start(ap, format);
+    int rc = vsnprintf(str, size, format, ap);
+    va_end(ap);
+
+    if (size && rc >= size)
+        return strlen(str);  // return actual # of bytes written
 
 Review comment:
   Hmmm.... I suppose size - 1 would work (snprintf return count excludes the null byte).
   I'll give it a try.
   

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