Clang Flag: -Wregister / -Wno-register

The Clang compiler flags -Wregister and -Wno-register are related to the use of the register storage class specifier in C and C++. The register keyword is a hint to the compiler that a variable should be stored in a register for fast access. However, its usage has become deprecated and incompatible with modern C++ standards, specifically starting with C++17, where its usage is disallowed. The -Wregister flag is not active by default, indicating that there are no warnings or errors generated specifically for the absence of this flag. This is because the considerations surrounding the register keyword are now largely managed by compilers and do not require explicit instruction from the developer. Conversely, the -Wno-register flag, which is active by default, suppresses warnings or errors related to the usage of the register storage class specifier. This is especially relevant when migrating legacy codebases to modern C++ standards or when aiming to silence warnings for code that still uses the register keyword for compatibility reasons. Using the -Wno-register flag allows developers to compile code that includes the register keyword without encountering errors or warnings related to its deprecation and incompatibility with C++17. In summary, the -Wno-register flag serves a crucial role in managing compatibility and warning verbosity for developers dealing with the transition from older standards that supported the register keyword to newer standards that do not.

AI Generated

Subroups

• -Wdeprecated-register (1 element)

Warnings/Remarks

Default Active (Deactivate with -Wno-register)

ext_register_storage_class	error: ISO C++17 does not allow 'register' storage class specifier
warn_deprecated_register	warning: 'register' storage class specifier is deprecated and incompatible with C++17

Default Inactive (Activate with -Wregister)

None