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sys/time_units.h: Work around clang div-by-zero warning

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clang emits a warning for this code:

  foo.c:1:25: warning: division by zero is undefined [-Wdivision-by-zero]
  int i = (10 > 100 ? (20 / (10 / 100)) : (20 * (100 / 10)));
	                        ^ ~~~~~~~~~~

The warning is generated for code whose value does not affect the
expression result, but technically it is still 'undefined behavior'.

Work around this warning by checking for a zero divisor and substituting
one to make the compiler happy.

Signed-off-by: Keith Packard <keithp@keithp.com>
This commit is contained in:
Keith Packard
2023-10-05 10:28:07 -07:00
committed by Johan Hedberg
parent f2af4a7bfd
commit ea61c8c1bd
1 changed files with 15 additions and 5 deletions
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20
include/zephyr/sys/time_units.h
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@@ -138,6 +138,16 @@ static TIME_CONSTEXPR inline int sys_clock_hw_cycles_per_sec(void)
(__round_up) ? ((__from_hz) / (__to_hz)) - 1 : \
0)
/* Clang emits a divide-by-zero warning even though the int_div macro
* results are only used when the divisor will not be zero. Work
* around this by substituting 1 to make the compiler happy.
*/
#ifdef __clang__
#define z_tmcvt_divisor(a, b) ((a) / (b) ?: 1)
#else
#define z_tmcvt_divisor(a, b) ((a) / (b))
#endif
/*
* Compute the offset needed to round the result correctly when
* the conversion requires a full mul/div
@@ -154,12 +164,12 @@ static TIME_CONSTEXPR inline int sys_clock_hw_cycles_per_sec(void)
((uint32_t)((__t) + \
z_tmcvt_off_div(__from_hz, __to_hz, \
__round_up, __round_off)) / \
((__from_hz) / (__to_hz))) \
z_tmcvt_divisor(__from_hz, __to_hz)) \
: \
(uint32_t) (((uint64_t) (__t) + \
z_tmcvt_off_div(__from_hz, __to_hz, \
__round_up, __round_off)) / \
((__from_hz) / (__to_hz))) \
z_tmcvt_divisor(__from_hz, __to_hz)) \
)
/* Integer multiplication 32-bit conversion */
@@ -173,9 +183,9 @@ static TIME_CONSTEXPR inline int sys_clock_hw_cycles_per_sec(void)
/* Integer division 64-bit conversion */
#define z_tmcvt_int_div_64(__t, __from_hz, __to_hz, __round_up, __round_off) \
((uint64_t) (__t) + z_tmcvt_off_div(__from_hz, __to_hz, \
__round_up, __round_off)) / \
((__from_hz) / (__to_hz))
(((uint64_t) (__t) + z_tmcvt_off_div(__from_hz, __to_hz, \
__round_up, __round_off)) / \
z_tmcvt_divisor(__from_hz, __to_hz))
/* Integer multiplcation 64-bit conversion */
#define z_tmcvt_int_mul_64(__t, __from_hz, __to_hz) \