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[PATCH 10/12] Warn when gettimeofday is called with non-null tzp argument.
- From: Zack Weinberg <zackw at panix dot com>
- To: libc-alpha at sourceware dot org
- Cc: Joseph Myers <joseph at codesourcery dot com>, Florian Weimer <fweimer at redhat dot com>, Lukasz Majewski <lukma at denx dot de>, Alistair Francis <alistair23 at gmail dot com>, Stepan Golosunov <stepan at golosunov dot pp dot ru>, Arnd Bergmann <arnd at arndb dot de>
- Date: Tue, 20 Aug 2019 09:21:50 -0400
- Subject: [PATCH 10/12] Warn when gettimeofday is called with non-null tzp argument.
- References: <20190820132152.24100-1-zackw@panix.com>
At this stage I don’t think we can issue warnings for settimeofday
with a non-null tzp argument, nor for arbitrary use of struct
timezone. But we can warn about gettimeofday with non-null tzp.
This uses a macro instead of an inline (fortify-style) function
because I got false positives with an inline, even with GCC 9.
* time/sys/time.h (__timezone_ptr_t): Delete.
(gettimeofday): Always declare second argument with type ‘void *’.
When possible, wrap with a macro that detects non-null and
non-constant second argument and issues a warning.
Improve commentary.
(settimeofday): Improve commentary.
* time/gettimeofday.c (gettimeofday):
Declare second argument as type ‘void *’.
---
time/gettimeofday.c | 4 ++--
time/sys/time.h | 36 +++++++++++++++++++++++++-----------
2 files changed, 27 insertions(+), 13 deletions(-)
diff --git a/time/gettimeofday.c b/time/gettimeofday.c
index 22a996a220..bd1fc3cb5e 100644
--- a/time/gettimeofday.c
+++ b/time/gettimeofday.c
@@ -23,10 +23,10 @@
If *TZ is not NULL, clear it.
Returns 0 on success, -1 on errors. */
int
-__gettimeofday (struct timeval *tv, struct timezone *tz)
+__gettimeofday (struct timeval *restrict tv, void *restrict tz)
{
if (__glibc_unlikely (tz != 0))
- memset (tz, 0, sizeof *tz);
+ memset (tz, 0, sizeof (struct timezone));
struct timespec ts;
if (__clock_gettime (CLOCK_REALTIME, &ts))
diff --git a/time/sys/time.h b/time/sys/time.h
index 5dbc7fc627..1b6c112274 100644
--- a/time/sys/time.h
+++ b/time/sys/time.h
@@ -54,23 +54,37 @@ struct timezone
int tz_minuteswest; /* Minutes west of GMT. */
int tz_dsttime; /* Nonzero if DST is ever in effect. */
};
-
-typedef struct timezone *__restrict __timezone_ptr_t;
-#else
-typedef void *__restrict __timezone_ptr_t;
#endif
-/* Get the current time of day and timezone information,
- putting it into *TV and *TZ. If TZ is NULL, *TZ is not filled.
- Returns 0 on success, -1 on errors.
- NOTE: This form of timezone information is obsolete.
- Use the functions and variables declared in <time.h> instead. */
+/* Get the current time of day, putting it into *TV.
+ If TZ is not null, *TZ must be a struct timezone, and both fields
+ will be set to zero.
+ Calling this function with a non-null TZ is obsolete;
+ use localtime etc. instead.
+ This function itself is semi-obsolete;
+ most callers should use time or clock_gettime instead. */
extern int gettimeofday (struct timeval *__restrict __tv,
- __timezone_ptr_t __tz) __THROW __nonnull ((1));
+ void *__restrict __tz) __THROW __nonnull ((1));
+
+#if __GNUC_PREREQ (4,3)
+/* Issue a warning for use of gettimeofday with a non-null __tz argument. */
+__warndecl (__warn_gettimeofday_timezone,
+ "gettimeofday with non-null or non-constant timezone parameter;"
+ " this is obsolete and inaccurate, use localtime instead");
+
+#define gettimeofday(__tv, __tz) \
+ (((!__builtin_constant_p (__tz) || (__tz) != 0) \
+ ? __warn_gettimeofday_timezone () \
+ : (void) 0), \
+ (gettimeofday) (__tv, __tz))
+#endif
#ifdef __USE_MISC
/* Set the current time of day and timezone information.
- This call is restricted to the super-user. */
+ This call is restricted to the super-user.
+ Setting the timezone in this way is obsolete, but we don't yet
+ warn about it because it still has some uses for which there is
+ no alternative. */
extern int settimeofday (const struct timeval *__tv,
const struct timezone *__tz)
__THROW;
--
2.23.0.rc1