Which Data Types Guarantee Atomic Reads and Writes on a 64-bit Linux System Using GCC?

Which data types have naturally atomic reads and writes on a 64-bit computer with a 64-bit x86-64 processor running Linux using the gcc compiler and gnu language?

While ISO C and C make no guarantees of atomic operations for any data type, the behavior may vary depending on the specific implementation. Here's how different types are handled in the context of atomic operations for a 64-bit computer running Linux using the gcc compiler and gnu language:

• Atomic with respect to signals:

  The sig_atomic_t type is guaranteed to have single-instruction reads and writes, making it atomic with respect to signals. This ensures that a signal handler invoked in the current thread will see either the old or new value of a sig_atomic_t variable.

• Atomic with respect to threads:

  To ensure atomic operations with respect to multiple threads, you must explicitly use _Atomic or std::atomic. Without these constructs, variables are not guaranteed to be atomic, even if the underlying hardware supports atomic operations for specific data types.

Additionally, it's crucial to understand that compiler optimizations may affect how variables are accessed. Even if a variable is inherently atomic, the compiler may optimize its access in a non-atomic manner. To ensure the intended behavior, it's always advisable to use _Atomic or std::atomic for variables that require atomic operations.

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