Clang Flag: -Wc++98-compat / -Wno-c++98-compat

The Clang compiler flags -Wc++98-compat and -Wno-c++98-compat are used to manage warnings related to C++98 compatibility. Specifically, -Wc++98-compat activates warnings that flag constructs in the code that are incompatible with the C++98 standards. This is particularly useful for developers aiming to maintain compatibility with older C++ standards or for projects that must be portable across environments where only C++98 standard is supported. Given that there are no default active elements for -Wno-c++98-compat as indicated by the absence of related elements under "Default Active (Deactivate with -Wno-c++98-compat)", this part of the flag does not require further elaboration. On the other hand, the -Wc++98-compat flag is default inactive, which means it requires explicit activation to enforce C++98 compatibility checks. When enabled, it examines a wide array of features introduced in C++ standards post-C++98, such as alias declarations, alignas specifier, attributes, auto type specifier, constexpr, and many more, flagging those that are not compatible with the C++98 standard. By invoking this flag, developers can identify and refactor such features to adhere to C++98 standards, ensuring broader compatibility of their codebase. Utilizing -Wc++98-compat is essential for projects where compliance with C++98 is crucial, either due to legacy system requirements, cross-platform portability concerns, or specific project guidelines that dictate adherence to older standards. This flag supplements the thorough review and manual code adjustments by programmatically highlighting incompatibilities, thus streamlining the process of ensuring C++98 compatibility.

AI Generated

Supergroups

• -Wc++98-compat-pedantic (217 elements)

Subroups

• -Wc++98-compat-local-type-template-args (1 element)
• -Wc++98-compat-unnamed-type-template-args (1 element)
• -Wpre-c++14-compat (11 elements)
• -Wpre-c++17-compat (17 elements)
• -Wpre-c++20-compat (27 elements)
• -Wpre-c++23-compat (15 elements)

Warnings/Remarks

Default Active (Deactivate with -Wno-c++98-compat)

None

Default Inactive (Activate with -Wc++98-compat)

warn_cxx98_compat_alias_declaration	warning: alias declarations are incompatible with C++98
warn_cxx98_compat_alignas	warning: 'alignas' is incompatible with C++98
warn_cxx98_compat_alignof	warning: alignof expressions are incompatible with C++98
warn_cxx98_compat_attribute	warning: [[]] attributes are incompatible with C++ standards before C++11
warn_cxx98_compat_auto_type_specifier	warning: 'auto' type specifier is incompatible with C++98
warn_cxx98_compat_constexpr	warning: 'constexpr' specifier is incompatible with C++98
warn_cxx98_compat_ctor_list_init	warning: constructor call from initializer list is incompatible with C++98
warn_cxx98_compat_decltype	warning: 'decltype' type specifier is incompatible with C++98
warn_cxx98_compat_defaulted_deleted_function	warning: defaulted deleted function definitions are incompatible with C++98
warn_cxx98_compat_delegating_ctor	warning: delegating constructors are incompatible with C++98
warn_cxx98_compat_empty_scalar_initializer	warning: scalar initialized from empty initializer list is incompatible with C++98
warn_cxx98_compat_empty_sizeless_initializer	warning: initializing A from an empty initializer list is incompatible with C++98
warn_cxx98_compat_enum_fixed_underlying_type	warning: enumeration types with a fixed underlying type are incompatible with C++98
warn_cxx98_compat_enum_friend	warning: befriending enumeration type A is incompatible with C++98
warn_cxx98_compat_enum_nested_name_spec	warning: enumeration type in nested name specifier is incompatible with C++98
warn_cxx98_compat_explicit_conversion_functions	warning: explicit conversion functions are incompatible with C++98
warn_cxx98_compat_for_range	warning: range-based for loop is incompatible with C++98
warn_cxx98_compat_friend_is_member	warning: friend declaration naming a member of the declaring class is incompatible with C++98
warn_cxx98_compat_generalized_initializer_lists	warning: generalized initializer lists are incompatible with C++98
warn_cxx98_compat_goto_into_protected_scope	warning: jump from this goto statement to its label is incompatible with C++98
warn_cxx98_compat_indirect_goto_in_protected_scope	warning: jump from this indirect asm goto statement to one of its possible targets is incompatible with C++98
warn_cxx98_compat_initializer_list_init	warning: initialization of initializer_list object is incompatible with C++98
warn_cxx98_compat_inline_namespace	warning: inline namespaces are incompatible with C++98
warn_cxx98_compat_lambda	warning: lambda expressions are incompatible with C++98
warn_cxx98_compat_less_colon_colon	warning: '<::' is treated as digraph '<:' (aka '[') followed by ':' in C++98
warn_cxx98_compat_literal_operator	warning: literal operators are incompatible with C++98
warn_cxx98_compat_literal_ucn_control_character	warning: universal character name referring to a control character is incompatible with C++98
warn_cxx98_compat_literal_ucn_escape_basic_scs	warning: specifying character 'A' with a universal character name is incompatible with C++98
warn_cxx98_compat_noexcept_decl	warning: noexcept specifications are incompatible with C++98
warn_cxx98_compat_noexcept_expr	warning: noexcept expressions are incompatible with C++98
warn_cxx98_compat_non_static_member_use	warning: use of non-static data member A in an unevaluated context is incompatible with C++98
warn_cxx98_compat_nonclass_type_friend	warning: non-class friend type A is incompatible with C++98
warn_cxx98_compat_nonstatic_member_init	warning: default member initializer for non-static data members is incompatible with C++98
warn_cxx98_compat_nontrivial_union_or_anon_struct_member	warning: anonymous struct union member B with a non-trivial default constructor copy constructor move constructor copy assignment operator move assignment operator destructor is incompatible with C++98
warn_cxx98_compat_nullptr	warning: 'nullptr' is incompatible with C++98
warn_cxx98_compat_override_control_keyword	warning: 'A' keyword is incompatible with C++98
warn_cxx98_compat_pass_non_pod_arg_to_vararg	warning: passing object of trivial but non-POD type A through variadic function block method constructor is incompatible with C++98
warn_cxx98_compat_raw_string_literal	warning: raw string literals are incompatible with C++98
warn_cxx98_compat_ref_qualifier	warning: reference qualifiers on functions are incompatible with C++98
warn_cxx98_compat_reference_list_init	warning: reference initialized from initializer list is incompatible with C++98
warn_cxx98_compat_rvalue_reference	warning: rvalue references are incompatible with C++98
warn_cxx98_compat_scoped_enum	warning: scoped enumerations are incompatible with C++98
warn_cxx98_compat_sfinae_access_control	warning: substitution failure due to access control is incompatible with C++98
warn_cxx98_compat_static_assert	warning: 'static_assert' declarations are incompatible with C++98
warn_cxx98_compat_static_data_member_in_union	warning: static data member A in union is incompatible with C++98
warn_cxx98_compat_switch_into_protected_scope	warning: jump from switch statement to this case label is incompatible with C++98
warn_cxx98_compat_template_arg_extra_parens	warning: redundant parentheses surrounding address non-type template argument are incompatible with C++98
warn_cxx98_compat_template_arg_null	warning: use of null pointer as non-type template argument is incompatible with C++98
warn_cxx98_compat_template_arg_object_internal	warning: non-type template argument referring to function object B with internal linkage is incompatible with C++98
warn_cxx98_compat_template_outside_of_template	warning: use of 'template' keyword outside of a template is incompatible with C++98
warn_cxx98_compat_template_parameter_default_in_function_template	warning: default template arguments for a function template are incompatible with C++98
warn_cxx98_compat_trailing_return_type	warning: trailing return types are incompatible with C++98
warn_cxx98_compat_two_right_angle_brackets	warning: consecutive right angle brackets are incompatible with C++98 (use '> >')
warn_cxx98_compat_typename_outside_of_template	warning: use of 'typename' outside of a template is incompatible with C++98
warn_cxx98_compat_unelaborated_friend_type	warning: befriending B without ' struct interface union class enum ' keyword is incompatible with C++98
warn_cxx98_compat_unicode_literal	warning: unicode literals are incompatible with C++98
warn_cxx98_compat_unicode_type	warning: 'A' type specifier is incompatible with C++98
warn_cxx98_compat_using_decl_constructor	warning: inheriting constructors are incompatible with C++98
warn_cxx98_compat_variadic_templates	warning: variadic templates are incompatible with C++98
warn_cxx98_compat_template_arg_local_type	warning: local type A as template argument is incompatible with C++98
warn_cxx98_compat_template_arg_unnamed_type	warning: unnamed type as template argument is incompatible with C++98
warn_cxx11_compat_constexpr_body_invalid_stmt	warning: use of this statement in a constexpr function constructor is incompatible with C++ standards before C++14
warn_cxx11_compat_constexpr_body_multiple_return	warning: multiple return statements in constexpr function is incompatible with C++ standards before C++14
warn_cxx11_compat_constexpr_body_no_return	warning: constexpr function with no return statements is incompatible with C++ standards before C++14
warn_cxx11_compat_constexpr_local_var	warning: variable declaration in a constexpr function constructor is incompatible with C++ standards before C++14
warn_cxx11_compat_constexpr_type_definition	warning: type definition in a constexpr function constructor is incompatible with C++ standards before C++14
warn_cxx11_compat_decltype_auto_type_specifier	warning: 'decltype(auto)' type specifier is incompatible with C++ standards before C++14
warn_cxx11_compat_deduced_return_type	warning: return type deduction is incompatible with C++ standards before C++14
warn_cxx11_compat_digit_separator	warning: digit separators are incompatible with C++ standards before C++14
warn_cxx11_compat_generic_lambda	warning: generic lambdas are incompatible with C++11
warn_cxx11_compat_init_capture	warning: initialized lambda captures are incompatible with C++ standards before C++14
warn_cxx11_compat_variable_template	warning: variable templates are incompatible with C++ standards before C++14
warn_cxx14_compat_class_template_argument_deduction	warning: class template argument deduction is incompatible with C++ standards before C++17   ; for compatibility, use explicit type name B
warn_cxx14_compat_constexpr_if	warning: constexpr if is incompatible with C++ standards before C++17
warn_cxx14_compat_constexpr_on_lambda	warning: constexpr on lambda expressions is incompatible with C++ standards before C++17
warn_cxx14_compat_decomp_decl	warning: decomposition declarations are incompatible with C++ standards before C++17
warn_cxx14_compat_fold_expression	warning: pack fold expression is incompatible with C++ standards before C++17
warn_cxx14_compat_init_statement	warning: if switch initialization statements are incompatible with C++ standards before C++17
warn_cxx14_compat_inline_variable	warning: inline variables are incompatible with C++ standards before C++17
warn_cxx14_compat_nested_namespace_definition	warning: nested namespace definition is incompatible with C++ standards before C++17
warn_cxx14_compat_star_this_lambda_capture	warning: by value capture of '*this' is incompatible with C++ standards before C++17
warn_cxx14_compat_static_assert_no_message	warning: 'static_assert' with no message is incompatible with C++ standards before C++17
warn_cxx14_compat_template_nontype_parm_auto_type	warning: non-type template parameters declared with A are incompatible with C++ standards before C++17
warn_cxx14_compat_template_template_param_typename	warning: template template parameter using 'typename' is incompatible with C++ standards before C++17
warn_cxx14_compat_u8_character_literal	warning: unicode literals are incompatible with C++ standards before C++17
warn_cxx14_compat_using_attribute_ns	warning: default scope specifier for attributes is incompatible with C++ standards before C++17
warn_cxx17_compat_multi_using_declaration	warning: use of multiple declarators in a single using declaration is incompatible with C++ standards before C++17
warn_cxx17_compat_using_declaration_pack	warning: pack expansion using declaration is incompatible with C++ standards before C++17
warn_for_range_begin_end_types_differ	warning: 'begin' and 'end' returning different types (A and B) is incompatible with C++ standards before C++17
warn_cxx17_compat_adl_only_template_id	warning: use of function template name with no prior function template declaration in function call with explicit template arguments is incompatible with C++ standards before C++20
warn_cxx17_compat_bitfield_member_init	warning: default member initializer for bit-field is incompatible with C++ standards before C++20
warn_cxx17_compat_capture_binding	warning: captured structured bindings are incompatible with C++ standards before C++20
warn_cxx17_compat_constexpr_body_invalid_stmt	warning: use of this statement in a constexpr function constructor is incompatible with C++ standards before C++20
warn_cxx17_compat_constexpr_ctor_missing_init	warning: constexpr constructor that does not initialize all members is incompatible with C++ standards before C++20
warn_cxx17_compat_constexpr_function_try_block	warning: function try block in constexpr function constructor is incompatible with C++ standards before C++20
warn_cxx17_compat_constexpr_local_var_no_init	warning: uninitialized variable in a constexpr function constructor is incompatible with C++ standards before C++20
warn_cxx17_compat_constexpr_union_ctor_no_init	warning: constexpr union constructor that does not initialize any member is incompatible with C++ standards before C++20
warn_cxx17_compat_constexpr_virtual	warning: virtual constexpr functions are incompatible with C++ standards before C++20
warn_cxx17_compat_decomp_decl_spec	warning: decomposition declaration declared 'B' with 'B' specifiers is incompatible with C++ standards before C++20
warn_cxx17_compat_defaulted_comparison	warning: defaulted comparison operators are incompatible with C++ standards before C++20
warn_cxx17_compat_defaulted_method_type_mismatch	warning: explicitly defaulting this default constructor copy constructor move constructor copy assignment operator move assignment operator destructor with a type different from the implicit type is incompatible with C++ standards before C++20
warn_cxx17_compat_equals_this_lambda_capture	warning: explicit capture of 'this' with a capture default of '=' is incompatible with C++ standards before C++20
warn_cxx17_compat_explicit_bool	warning: explicit(bool) is incompatible with C++ standards before C++20
warn_cxx17_compat_for_range_init_stmt	warning: range-based for loop initialization statements are incompatible with C++ standards before C++20
warn_cxx17_compat_init_capture_pack	warning: initialized lambda capture packs are incompatible with C++ standards before C++20
warn_cxx17_compat_inline_nested_namespace_definition	warning: inline nested namespace definition is incompatible with C++ standards before C++20
warn_cxx17_compat_lambda_def_ctor_assign	warning: default construction assignment of lambda is incompatible with C++ standards before C++20
warn_cxx17_compat_lambda_template_parameter_list	warning: explicit template parameter list for lambdas is incompatible with C++ standards before C++20
warn_cxx17_compat_missing_varargs_arg	warning: passing no argument for the '...' parameter of a variadic macro is incompatible with C++ standards before C++20
warn_cxx17_compat_spaceship	warning: '<=>' operator is incompatible with C++ standards before C++20
warn_cxx17_compat_template_nontype_parm_type	warning: non-type template parameter of type A is incompatible with C++ standards before C++20
warn_cxx17_compat_unicode_type	warning: 'char8_t' type specifier is incompatible with C++ standards before C++20
warn_cxx17_compat_using_decl_class_member_enumerator	warning: member using declaration naming a non-member enumerator is incompatible with C++ standards before C++20
warn_cxx17_compat_using_decl_non_member_enumerator	warning: member using declaration naming non-class 'A' enumerator is incompatible with C++ standards before C++20
warn_cxx17_compat_using_decl_scoped_enumerator	warning: using declaration naming a scoped enumerator is incompatible with C++ standards before C++20
warn_cxx17_compat_using_enum_declaration	warning: using enum declaration is incompatible with C++ standards before C++20
ext_subscript_overload	warning: overloaded A with no a defaulted more than one parameter is a C++23 extension
warn_cxx20_alias_in_init_statement	warning: alias declaration in this context is incompatible with C++ standards before C++23
warn_cxx20_compat_auto_expr	warning: 'auto' as a functional-style cast is incompatible with C++ standards before C++23
warn_cxx20_compat_consteval_if	warning: consteval if is incompatible with C++ standards before C++23
warn_cxx20_compat_constexpr_body_invalid_stmt	warning: use of this statement in a constexpr function constructor is incompatible with C++ standards before C++23
warn_cxx20_compat_constexpr_var	warning: definition of a static variable thread_local variable variable of non-literal type in a constexpr function constructor is incompatible with C++ standards before C++23
warn_cxx20_compat_decl_attrs_on_lambda	warning: an attribute specifier sequence B in this position is incompatible with C++ standards before C++23
warn_cxx20_compat_label_end_of_compound_statement	warning: label at end of compound statement is incompatible with C++ standards before C++23
warn_cxx20_compat_operator_overload_static	warning: declaring overloaded A as 'static' is incompatible with C++ standards before C++23
warn_cxx20_compat_size_t_suffix	warning: 'size_t' suffix for literals is incompatible with C++ standards before C++23
warn_cxx20_compat_static_lambda	warning: static lambdas are incompatible with C++ standards before C++23
warn_cxx23_compat_defaulted_comparison_constexpr_mismatch	warning: defaulted definition of equality three-way equality relational comparison operator three-way comparison operator that is declared constexpr consteval but   for which the corresponding implicit 'operator==' invokes a non-constexpr comparison function is incompatible with C++ standards before C++23
warn_cxx23_compat_pp_directive	warning: use of a '# elifdef elifndef ' directive is incompatible with C++ standards before C++23
warn_cxx23_compat_warning_directive	warning: #warning is incompatible with C++ standards before C++23
warn_cxx23_delimited_escape_sequence	warning: delimited named escape sequences are incompatible with C++ standards before C++23