Sig_atomic_t
sig_atomic_t is an integer type whose object evaluations and assignments are guaranteed to be indivisible with respect to signal handling.
Modern C, Third Edition
sig_atomic_t is an integer type whose object evaluation and assignment operations are guaranteed to be indivisible with respect to signal handling.
- How it is used
- Uses a signal-handler flag to record an interrupt condition for handling after the handler returns.
- How deep it goes
- Defines uninterruptible loads and stores, then explains why increment is unsafe; does not develop sig_atomic_t beyond its restricted guarantees.
- Examples
- Contrasts storing a signal number in a flag with incrementing a counter, and shows a lock-free atomic counter alternative.
- What you can do after
- Build a minimal signal handler from scratch that records a signal number in a volatile sig_atomic_t flag.
Modern C
sig_atomic_t is an integer C type whose object evaluations and assignments are guaranteed to be uninterruptible with respect to signal handling.
- How it is used
- Stores a signal number for a signal handler without an interruptible assignment.
- How deep it goes
- Defines uninterruptibility and limits the guarantee to loads and stores, not increments.
- Examples
- Uses a handler that stores its received signal number and contrasts it with signal counting.
- What you can do after
- Evaluate/understand when sig_atomic_t supports a handler’s load or store and why it should not serve as a counter.
Related concepts
- signal handlerused by · A signal handler is a function or mechanism that specifies or performs a response when a signal or notification is delivered.
- atomic typealternative to · An atomic type is a type whose supported accesses and operations are indivisible with respect to concurrent execution and provide defined synchronization semantics.
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