Clang Flag: -Wdangling / -Wno-dangling

The Clang compiler flags -Wdangling and -Wno-dangling are used to control warnings related to the potential misuse of references and pointers, which could lead to dangling references, pointers, or access to deallocated memory. Specifically, these flags target scenarios where objects may be destroyed at the end of a full-expression, leaving references or pointers to them invalid. The -Wdangling group includes various subflags designed to flag different instances of dangling issues, such as -Wdangling-field, -Wdangling-initializer-list, and -Wdangling-gsl. These subflags cover a range of situations from binding references to temporary objects, initializing pointers with stack addresses, to warnings about returning addresses of stack memory or local temporaries. As of the current state, the -Wdangling flag itself is set to be default inactive, meaning that the specific warnings it encompasses are not enabled by default. However, warnings that fall under the categories of -Wdangling-field, -Wdangling-initializer-list, -Wdangling-gsl, and -Wreturn-stack-address are activated by default. To suppress these types of warnings, developers can use the -Wno-dangling flag. In practice, enabling these warnings helps developers to identify and correct potentially unsafe code patterns that could result in undefined behavior due to accessing invalidated memory locations. It encourages best practices in managing object lifetimes and ensures safer memory management in applications compiled with Clang.

AI Generated

Subroups

• -Wdangling-field (4 elements)
• -Wdangling-initializer-list (1 element)
• -Wdangling-gsl (2 elements)
• -Wreturn-stack-address (3 elements)

Warnings/Remarks

Default Active (Deactivate with -Wno-dangling)

warn_dangling_variable	warning: temporary whose address is used as value of   implicitly bound to   reference member of local variable local variable reference array backing initializer list subobject of local variable local initializer list D   will be destroyed at the end of the full-expression
warn_unsupported_lifetime_extension	warning: sorry, lifetime extension of temporary backing array of initializer list created by aggregate initialization using default member initializer is not supported; lifetime of temporary backing array will end at the end of the full-expression
warn_bind_ref_member_to_parameter	warning: binding reference member A to stack allocated variable parameter B
warn_dangling_member	warning: reference backing array for 'std::initializer_list'   subobject of member A binds to is a temporary object whose lifetime is shorter than the lifetime of the constructed object
warn_init_ptr_member_to_parameter_addr	warning: initializing pointer member A with the stack address of variable parameter B
warn_new_dangling_reference	warning: temporary bound to reference member of allocated object will be destroyed at the end of the full-expression
warn_new_dangling_initializer_list	warning: array backing initializer list subobject of the allocated object the allocated initializer list will be destroyed at the end of the full-expression
warn_dangling_lifetime_pointer	warning: object backing the pointer will be destroyed at the end of the full-expression
warn_dangling_lifetime_pointer_member	warning: initializing pointer member A to point to a temporary object whose lifetime is shorter than the lifetime of the constructed object
warn_ret_addr_label	warning: returning address of label, which is local
warn_ret_local_temp_addr_ref	warning: returning address of reference to local temporary object
warn_ret_stack_addr_ref	warning: address of reference to stack memory associated with local variable parameter B returned

Default Inactive (Activate with -Wdangling)

None