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spinlock: Make sure C and C++ have the same sizeof(k_spinlock) value

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If CONFIG_SMP and SPIN_VALIDATE are both not defined the k_spinlock
struct will have no members. The result is that in C the sizeof
value of struct k_spinlock is 0 and in C++ it is 1.

This size difference causes problems when the k_spinlock
is embedded into another struct like k_msgq, because C and
C++ will have different ideas on the offsets of the members
that come after the k_spinlock member.

To prevent this we add a 1 byte dummy member to k_spinlock
when the user selects C++ support and k_spinlock would
otherwise be empty.

Signed-off-by: Erwin Rol <erwin@erwinrol.com>
This commit is contained in:
Erwin Rol 2019-09-15 20:33:14 +02:00 • committed by Maureen Helm
commit e6ffb3fdc4
1 changed files with 17 additions and 0 deletions
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17
include/spinlock.h
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@ -61,6 +61,23 @@ struct k_spinlock {
*/ */
uintptr_t thread_cpu; uintptr_t thread_cpu;
#endif #endif
#if defined(CONFIG_CPLUSPLUS) && !defined(CONFIG_SMP) && !defined(SPIN_VALIDATE)
/* If CONFIG_SMP and SPIN_VALIDATE are both not defined
* the k_spinlock struct will have no members. The result
* is that in C sizeof(k_spinlock) is 0 and in C++ it is 1.
*
* This size difference causes problems when the k_spinlock
* is embedded into another struct like k_msgq, because C and
* C++ will have different ideas on the offsets of the members
* that come after the k_spinlock member.
*
* To prevent this we add a 1 byte dummy member to k_spinlock
* when the user selects C++ support and k_spinlock would
* otherwise be empty.
*/
char dummy;
#endif
}; };
static ALWAYS_INLINE k_spinlock_key_t k_spin_lock(struct k_spinlock *l) static ALWAYS_INLINE k_spinlock_key_t k_spin_lock(struct k_spinlock *l)