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epan: don't use gmtime_s(). 

It has the "feature" that, if handed a negative value, it might just
exit.  gmtime() doesn't have that "feature", and is sufficiently
thread-safe for our purposes; use it instead, and check to make sure it
doesn't return a null pointer.

The previous fix for #17179 still used gmtime_s(); this doesn't, so it's
a better fix for #17179.


(cherry picked from commit bf265d7e7a)
This commit is contained in:
Guy Harris 2021-01-28 06:15:31 +00:00
parent e072a71256
commit 9bcc1785c1
1 changed files with 27 additions and 5 deletions
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32
epan/print.c
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@ -1273,8 +1273,10 @@ ek_write_field_value(field_info *fi, write_json_data* pdata)
gchar label_str[ITEM_LABEL_LENGTH];
char *dfilter_string;
const nstime_t *t;
struct tm *tm;
#ifndef _WIN32
struct tm tm_time;
gboolean success;
#endif
char time_string[sizeof("YYYY-MM-DDTHH:MM:SS")];
/* Text label */
@ -1304,12 +1306,32 @@ ek_write_field_value(field_info *fi, write_json_data* pdata)
case FT_ABSOLUTE_TIME:
t = (const nstime_t *)fvalue_get(&fi->value);
#ifdef _WIN32
success = (gmtime_s(&tm_time, &t->secs) == 0);
/*
* Do not use gmtime_s(), as it will call and
* exception handler if the time we're providing
* is < 0, and that will, by default, exit.
* ("Programmers not bothering to check return
* values? Try new Microsoft Visual Studio,
* with Parameter Validation(R)! Kill insufficiently
* careful programs - *and* the processes running them -
* fast!")
*
* We just want to report this as an unrepresentable
* time. It fills in a per-thread structure, which
* is sufficiently thread-safe for our purposes.
*/
tm = gmtime(&t->secs);
#else
success = (gmtime_r(&t->secs, &tm_time) != NULL);
/*
* Use gmtime_r(), because the Single UNIX Specification
* does *not* guarantee that gmtime() is thread-safe.
* Perhaps it is on all platforms on which we run, but
* this way we don't have to check.
*/
tm = gmtime_r(&t->secs, &tm_time);
#endif
if (success) {
strftime(time_string, sizeof(time_string), "%FT%T", &tm_time);
if (tm != NULL) {
strftime(time_string, sizeof(time_string), "%FT%T", tm);
} else {
g_snprintf(time_string, sizeof(time_string), "Not representable");
}