Technical Corrigendum for Atomic Operations in Signal Handlers

David Keaton

2014-10-29

The following is proposed as a technical corrigendum for DR 462 on atomic operations in signal handlers.

Proposed Technical Corrigendum

Change subclause 7.14.1.1 paragraph 5 from:

If the signal occurs other than as the result of calling the abort or raise function, the behavior is undefined if the signal handler refers to any object with static or thread storage duration that is not a lock-free atomic object other than by assigning a value to an object declared as volatile sig_atomic_t, or the signal handler calls any function in the standard library other than the abort function, the _Exit function, the quick_exit function, or the signal function with the first argument equal to the signal number corresponding to the signal that caused the invocation of the handler. Furthermore, if such a call to the signal function results in a SIG_ERR return, the value of errno is indeterminate.²⁵²⁾

to:

If the signal occurs other than as the result of calling the abort or raise function, the behavior is undefined if the signal handler refers to any object with static or thread storage duration that is not a lock-free atomic object other than by assigning a value to an object declared as volatile sig_atomic_t, or the signal handler calls any function in the standard library other than

• the abort function,

• the _Exit function,

• the quick_exit function,

• the atomic generic functions except atomic_init, when the atomic arguments are lock-free,

• the atomic_is_lock_free function with any atomic argument,

• or the signal function with the first argument equal to the signal number corresponding to the signal that caused the invocation of the handler. Furthermore, if such a call to the signal function results in a SIG_ERR return, the value of errno is indeterminate.²⁵²⁾

In subclause J.2 Undefined behavior, change:

A signal occurs other than as the result of calling the abort or raise function, and the signal handler refers to an object with static or thread storage duration that is not a lock-free atomic object other than by assigning a value to an object declared as volatile sig_atomic_t, or calls any function in the standard library other than the abort function, the _Exit function, the quick_exit function, or the signal function (for the same signal number) (7.14.1.1).

to:

A signal occurs other than as the result of calling the abort or raise function, and the signal handler refers to an object with static or thread storage duration that is not a lock-free atomic object other than by assigning a value to an object declared as volatile sig_atomic_t, or calls any function in the standard library other than the abort function, the _Exit function, the quick_exit function, the atomic generic functions (when the atomic arguments are lock-free) except atomic_init, the atomic_is_lock_free function with any atomic argument, or the signal function (for the same signal number) (7.14.1.1).