diff --git a/libcxx/include/__format/format_functions.h b/libcxx/include/__format/format_functions.h index 185148ccba531..0f0001272d40d 100644 --- a/libcxx/include/__format/format_functions.h +++ b/libcxx/include/__format/format_functions.h @@ -258,10 +258,12 @@ __handle_replacement_field(const _CharT* __begin, const _CharT* __end, if constexpr (same_as<_Ctx, __compile_time_basic_format_context<_CharT>>) { __arg_t __type = __ctx.arg(__r.__value); - if (__type == __arg_t::__handle) + if (__type == __arg_t::__none) + std::__throw_format_error("Argument index out of bounds"); + else if (__type == __arg_t::__handle) __ctx.__handle(__r.__value).__parse(__parse_ctx); - else - __format::__compile_time_visit_format_arg(__parse_ctx, __ctx, __type); + else if (__parse) + __format::__compile_time_visit_format_arg(__parse_ctx, __ctx, __type); } else _VSTD::__visit_format_arg( [&](auto __arg) { diff --git a/libcxx/test/std/utilities/format/format.functions/format_tests.h b/libcxx/test/std/utilities/format/format.functions/format_tests.h index 86d11f2c26be6..763cf4517bffd 100644 --- a/libcxx/test/std/utilities/format/format.functions/format_tests.h +++ b/libcxx/test/std/utilities/format/format.functions/format_tests.h @@ -2617,6 +2617,10 @@ void format_tests(TestFunction check, ExceptionTest check_exception) { check(SV("{"), SV("{{")); check(SV("}"), SV("}}")); + check(SV("{:^}"), SV("{{:^}}")); + check(SV("{: ^}"), SV("{{:{}^}}"), CharT(' ')); + check(SV("{:{}^}"), SV("{{:{{}}^}}")); + check(SV("{:{ }^}"), SV("{{:{{{}}}^}}"), CharT(' ')); // *** Test argument ID *** check(SV("hello false true"), SV("hello {0:} {1:}"), false, true);