Clang Flag: -Wnon-pod-varargs / -Wno-non-pod-varargs

The Clang compiler flags -Wnon-pod-varargs and -Wno-non-pod-varargs are associated with warnings related to the use of non-Plain Old Data (non-POD) types with variadic functions. These flags are crucial for developers who wish to ensure type safety and runtime behavior correctness when dealing with functions that accept a variable number of arguments. Activating -Wnon-pod-varargs is aimed at catching and warning about potential issues when non-POD types are passed to variadic functions or when non-POD types are specified with the va_arg macro. However, by default, this check is inactive, indicating that no elements are marked under the section for activation, suggesting that the compiler might not warn about these issues unless explicitly instructed to do so. The counterpart, -Wno-non-pod-varargs, is used to suppress warnings generated by passing non-POD types to variadic arguments. This flag becomes relevant in projects where such warnings are understood by the developers and deemed non-critical or where legacy codebases need to be compiled without modifying the code to meet the non-POD vararg requirements. Based on the article, this flag is set active by default, meaning the compiler will not warn about non-POD type issues unless the developer explicitly deactivates this behavior through the flag. Given the complexities associated with variadic functions and the nuanced behaviors of POD versus non-POD types in C++, understanding and appropriately applying these flags can significantly aid in maintaining both the portability and correctness of codebases that leverage variadic functionality.

AI Generated

Supergroups

• -Wclass-varargs (5 elements)

Warnings/Remarks

Default Active (Deactivate with -Wno-non-pod-varargs)

warn_cannot_pass_non_pod_arg_to_vararg	error: cannot pass object of non-POD non-trivial type B through variadic function block method constructor ; call will abort at runtime
warn_non_pod_vararg_with_format_string	error: cannot pass non-POD non-trivial object of type B to variadic function block method constructor ; expected type from format string was D
warn_second_parameter_to_va_arg_not_pod	error: second argument to 'va_arg' is of non-POD type A
warn_second_parameter_to_va_arg_ownership_qualified	error: second argument to 'va_arg' is of ARC ownership-qualified type A

Default Inactive (Activate with -Wnon-pod-varargs)

None