On 10/24/25 01:25, Jakub Kicinski wrote:
On Tue, 21 Oct 2025 12:43:30 +0100 Gustavo A. R. Silva wrote:struct ip_options_data { - struct ip_options_rcu opt; - char data[40]; + TRAILING_OVERLAP(struct ip_options_rcu, opt, opt.__data, + char data[40]; + ); };Is there a way to reserve space for flexible length array on the stack without resorting to any magic macros? This struct has total of 5 users.
Not that I know of. That's the reason why we had to implement macros like TRAILING_OVERLAP(), DEFINE_FLEX(), DEFINE_RAW_FLEX(). Regarding these three macros, the simplest and least intrusive one to use is actually TRAILING_OVERLAP(), when the flex-array member is not annotated with the counted_by attribute (otherwise, DEFINE_FLEX() would be preferred). Of course, the most straightforward alternative is to use fixed-size arrays if flex arrays are not actually needed. Thanks -Gustavo
