kgiusti commented on a change in pull request #679: DISPATCH-1566: fix
safe_snptrintf
URL: https://github.com/apache/qpid-dispatch/pull/679#discussion_r379086687
##########
File path: src/router_core/terminus.c
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@@ -75,24 +76,34 @@ void qdr_terminus_free(qdr_terminus_t *term)
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,
...)
-{
+size_t safe_snprintf(char *str, size_t size, const char *format, ...) {
+ // max size allowed must be INT_MAX (since vsnprintf reutrns an int)
+ if (size == 0 || size > INT_MAX) {
+ //TODO log a warning somewhere?
+ return 0;
+ }
+ int max_possible_return_value = (int)(size - 1);
va_list ap;
va_start(ap, format);
int rc = vsnprintf(str, size, format, ap);
va_end(ap);
- if (size && rc >= size)
- return size - 1; // return actual # of bytes written (excluding null)
- return rc;
-}
+ if (rc < 0) { // parsing error!
+ //TODO log a warning somewhere?
+ return 0;
Review comment:
Good idea checking for rc < 0. I'd suggest terminating the string before
returning zero however since it may be unterminated. Example
if (rc < 0) {
if (size > 0 && str) *str = 0;
return 0;
}
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